Founded in 1973, Meteorological Science and Technology（Bimonthly, ISSN：1671—6345, CN 11—2374/P）is governed by China Meteorological Administration, and jointly sponsored by CMA Meteorological Observation Centre, Chinese Academy of Meteorological Sciences, Beijing Meteorological Service, National Satellite Meteorological Center and National Meteorological Information Centre. As a comprehensive technical journal with engineering features, Meteorological Science and Technology aims to provide a platform for the exchange of knowledge, technology, and experience for scientific and technical personnel. The journal mainly publishes research articles that reflect new theories, methods, and technologies in atmospheric science and related sciences. Main columns include Atmospheric Sounding and Information Technology; Weather & Climate and Numerical Forecasting; Applied Meteorology and Scientific Experiments, and Practical Techniques.

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    2025,53(4):457-467, DOI: 10.19517/j.1671-6345.20240346
    Abstract:
    Global climate warming leads to an increase in the frequency and intensity of forest and grassland fires. During the rescue process of forest and grassland fires, wind is the most important meteorological factor affecting the spread of the fire. It determines not only the speed of the fire’s spread but also the area and direction of the fire’s spread. Moreover, the changeable wind field information under complex terrain conditions further increases the risks for firefighting efforts and the safety guarantee of rescue workers. The wind lidar, which has the capabilities of high spatial and temporal resolution and non-contact measurement, is of great significance for the prevention and control of forest fires and the on-site rescue command. However, the detection range of the existing wind lidar is difficult to meet the demand for long-distance wind field monitoring at the forest and grassland fire site, which restricts the precise monitoring and early warning of secondary disasters at the forest fire rescue site. Therefore, The study conducts research from two aspects: high-power laser emission technology and clear-sky weak signal algorithm, and comprehensively improves the detection range from both hardware technology and data processing aspects. The high-power laser emission technology mainly includes low-noise narrow linewidth technology, multi-stage pump source amplification technology, and Brillouin scattering suppression technology, so as to achieve high-power output as a whole and ensure the measurement accuracy, sensitivity, and reliability of the lidar system. In terms of data processing, the maximum likelihood discrete spectrum peak estimation algorithm and the optimised power spectrum frequency shift estimation algorithm are used to improve the detection ability of the lidar for weak signals. The research results show that after adopting the above technologies and algorithms, the wind lidar achieves large-scale wind field measurement over a range of 15 km. The data acquisition rate exceeds 90% at 12,600 metres, reaches more than 80% at 14,400 metres, and is above 75% at 15,000 metres, with a significant improvement in detection ability. In terms of detection accuracy, there is a high degree of consistency when compared with the data from the wind measurement tower. The determination coefficients of the horizontal wind speed and wind direction at the two heights of 77 metres and 103 metres between the wind lidar and the wind measurement tower are all above 0.99, the deviation of the linear regression fitting degree is all below 0.005, the average deviation of the wind speed is below 0.05 m/s, and the average deviation of the wind direction is below 2 degrees.
    2025,53(4):468-478, DOI: 10.19517/j.1671-6345.20240339
    Abstract:
    The deep learning-based radar echo extrapolation method is widely applied to the challenging task of short-term precipitation forecasting. However, existing methods still face issues with prediction accuracy, and when dealing with high-resolution and long-time sequence data, the training speed tends to be slow. To address these problems, this paper proposes a deep learning model based on sparse fusion attention - PFA-TransUNet (ProbSparse Fusion Attention TransUNet). This model is an encoder-decoder architecture, where a multi-layer Transformer is introduced in the encoder path. It then decomposes the traditional multi-head self-attention mechanism into computations in the spatiotemporal dimensions, allowing for the full integration of spatiotemporal information. In addition, the sparse attention method is incorporated to reduce the computational complexity of self-attention, significantly shortening the training time. Experimental results on the Hebei Province radar dataset show that compared to other advanced classical models, PFA-TransUNet outperforms them in various evaluation metrics such as extrapolation accuracy, Mean Squared Error (MSE), Structural Similarity Index (SSIM), Critical Success Index (CSI) at 20, 30, and 40 dBz, and training speed. The model demonstrates exceptional overall performance. In recent years, radar echo extrapolation becomes an increasingly important approach in precipitation forecasting, especially for nowcasting (short-term forecasting) tasks, where the ability to predict precipitation with high accuracy and efficiency is critical. However, due to the complex spatiotemporal nature of radar echoes, previous methods struggle to efficiently capture both spatial and temporal dependencies, which leads to suboptimal forecasting results. Furthermore, the computational cost associated with high-resolution and long-time series data further hampers the efficiency of current deep learning models. PFA-TransUNet addresses these limitations by incorporating a sparse attention mechanism, which helps reduce the computational load without sacrificing model performance. Traditional self-attention mechanisms in Transformer models can be computationally expensive due to the quadratic complexity of attention calculations, especially when applied to large datasets. By leveraging sparse attention, the proposed model focuses on the most relevant parts of the input data, thus improving computational efficiency and speeding up training. Another key feature of PFA-TransUNet is its ability to effectively model spatiotemporal dependencies. By decomposing the multi-head self-attention into spatiotemporal dimensions, the model captures the intricate relationships between space and time, leading to more accurate extrapolations of radar echoes. This is crucial in precipitation forecasting, as both spatial distribution and temporal evolution play a significant role in the prediction accuracy. The experimental results from the Hebei radar dataset indicate that PFA-TransUNet achieves superior performance compared to traditional models. The model shows a substantial improvement in forecast accuracy, with lower MSE values and higher SSIM scores, indicating better preservation of the structure of radar echoes. Furthermore, the model excels in terms of CSI at different dBz thresholds, demonstrating its robustness in detecting precipitation events under various conditions. Most importantly, the model’s training speed is significantly improved due to the sparse attention mechanism, making it suitable for real-time forecasting applications. In conclusion, PFA-TransUNet presents a promising solution for radar echo extrapolation tasks, especially in the context of short-term precipitation forecasting. Its combination of sparse fusion attention and spatiotemporal modelling makes it a powerful tool for improving the accuracy and efficiency of radar-based forecasting systems.
    2025,53(4):479-487, DOI: 10.19517/j.1671-6345.20240172
    Abstract:
    GNSS receivers and antennas are set up in Beijing to receive the second-level signals of the GNSS system. Data quality checks are conducted using software. Leveraging precise ephemeris data from the BeiDou Navigation Satellite System (BDS) B2b signal, real-time zenith total delay (ZTD) and precipitable water vapour (PWV) retrieval experiments are conducted using BDS Precise Point Positioning (PPP) techniques, single GPS, and their integrated solutions. These results are systematically compared against ZTD/PWV estimates derived from BDS/GPS dual-difference network solutions, radiosonde observations, and ERA5 reanalysis datasets. The results show that the average signal-to-noise ratio of the GNSS signal is greater than 35, and the multipath effect is better than 0.5 m, ensuring robust observational conditions for inversion modelling. Compared with the double-difference network solution, the average deviation of the tropospheric delay inversion based on BeiDou precise point positioning is 4.5 mm, the root mean square error is 9.94 mm, and the correlation coefficient is 90%. The corresponding PWV inversion average deviation is 0.35 mm, the root mean square error is 1.33 mm, and the correlation coefficient is 96%. Compared with radiosonde, the average deviation of the tropospheric delay inversion is 5.83 mm, the RMSE is 7.38 mm, and the correlation coefficient is 95.07%. The corresponding PWV inversion average deviation is 1.03 mm, the root mean square error is 1.72 mm, and the correlation coefficient is 94.45%. This indicates that the ZTD/PWV inversion technology derived from BDS makes single-system and single-point solutions possible. This method adopts a distributed computing strategy, avoiding the bandwidth and storage pressure of returning the solution data to the central station at the station end in the past, improving the real-time performance of water vapour solutions, and can represent the trend of water vapour change. It is of great significance for the monitoring and early warning of weather phenomena and meteorological disasters related to water vapour.
    2025,53(4):488-496, DOI: 10.19517/j.1671-6345.20240324
    Abstract:
    The China Meteorological Administration Satellite Broadcasting System (CMACast system), owing to its extensive coverage and the significant advantage of being intercontinental and end-to-end, unaffected by ground communication conditions, becomes one of the crucial communication means for global meteorological data distribution services. As the China Meteorological Administration continuously enhances its global monitoring, global forecasting, and global service capabilities, the requirements for providing meteorological data distribution services to international users, especially those along the Belt and Road lnitiative, become increasingly demanding. However, the CMACast system has an obvious service shortcoming in that its broadcast signal coverage is limited to the Asia-Pacific region. To meet the global meteorological service demands, the satellite broadcasting system of the meteorological informatisation system project is comprehensively upgraded. Among these upgrades, the expansion of the broadcast coverage area is one of the most significant. The selection of transponders for the new broadcast communication satellites and the design of broadcast parameters are key issues that need to be addressed with priority. Through a survey of all communication satellite resources over China, based on the coverage area of satellite C transponders, four communication satellites are initially selected as the research objects from 20 on-orbit communication satellites of CITIC Satcom and China Satcom. Through a comprehensive comparison and analysis of the coverage area, signal strength, transponder frequency, and the coverage of existing users of these four satellites, the results show that the AsiaSat 7 is the optimal choice. Therefore, based on the AsiaSat 7, the broadcast links to the Belt and Road lnitiative regions and countries are calculated and analysed respectively. The results indicate that using the AsiaSat 7 can meet the requirements of the broadcast service, verifying the correctness of choosing the AsiaSat 7 as the broadcast transmission design. At the same time, to make the new broadcast system compatible with all existing users, actual tests are carried out on various modulation methods, coding rates, roll-off factors, and broadcasting rates under the condition of antennas with different receiving apertures. Through actual tests, 8PSK modulation, 3/4 coding rate, and 0.1 roll-off factor are optimally selected as the operation parameters for the broadcast service. This not only meets the needs of the expanded and upgraded broadcast coverage but also is compatible with all existing users. The achievements are applied to the upgrade and construction of the CMACast system in the meteorological informatisation system project. As a result, the coverage of the new-generation CMACast system is expanded from the Asia-Pacific region to the Belt and Road lnitiative regions such as the Middle East and Africa, enhancing the information network support for meteorological services in these regions.
    2025,53(4):497-507, DOI: 10.19517/j.1671-6345.20240298
    Abstract:
    The development of refined tropical cyclone (TC) forecasting operations relies on high-resolution regional TC numerical forecasting. However, when faced with both the characteristic of expensive computational consumption of high-resolution models and the characteristic of the wide range of TC forecasting responsibility areas, it is difficult for the existing numerical forecasting techniques to meet the high timeliness requirements in operational high-resolution TC forecasting. High-resolution numerical models face challenges in balancing computational demands, forecast timeliness, and prediction accuracy for TC forecasting operations. To save computational resources and meet high timeliness requirements while ensuring TC forecast accuracy, this study proposes an adaptive setting-up approach of a limited area for the short-term forecast of TC by combining an adaptive objective calculation method for the TC simulation domain with multi-TC coexistence processing technology. This approach dynamically adjusts the position and size of the high-resolution TC model simulation domain based on the forecast timeliness and the actual situation of the TC. By automatically providing a scientifically reasonable simulation domain, the computer resource consumption is reduced without losing forecasting skills. Applying this approach to the high-resolution CMA-MESO model, a High-Resolution Typhoon Numerical Prediction System (HRTYM) is established. The numerical experiments and comparative analysis are carried out using Typhoon Lekima (2019) and 16 major typhoon events in 2020 and 2021. The experimental results of Typhoon Lekima show that, compared with the 9 km-resolution operational model (CMA-TYM), the 3 km-resolution HRTYM requires fewer computational resources with model integration time reduced by 11.2%-17.5% and storage space reduced by 58.6%-66.7%, the TC track forecast error decreases by 20.7%-61.0%, and the TS scores for 24-hour rainstorm and heavy rainstorm predictions improve significantly. The results of batch experiments in 2020 show that after 24-48 hours of mode integration, the track error of the 3 km-resolution HRTYM decreases by 3.44-34.91 km compared to the 9 km-resolution CMA-TYM, and the results of batch experiments in 2021 show that after 27-48 hours of mode integration, the track error of the 3 km-resolution HRTYM decreases by 0.6-22.35 km compared to the 9 km-resolution CMA-TYM. The results of batch experiments in 2020 and 2021 demonstrate that HRTYM exhibits superior track prediction skill over CMA-TYM beyond 27 hours. The high-resolution TC numerical prediction system applying the adaptive setting-up approach of a limited area for the short-term forecast of TC proposed in this study effectively reduces the cost of computing resources and computer storage space resources and ensures the skill of TC numerical prediction at the same time.
    2025,53(4):508-519, DOI: 10.19517/j.1671-6345.20240309
    Abstract:
    With the continuous improvement of the horizontal resolution of the numerical weather prediction model, cumulus clouds are not distinguishable by the grid scale in the “grey area” (1-10 km) of the convective parameterisation scheme, making the traditional cumulus convective parameterisation scheme difficult to apply to the simulation of precipitation at different resolutions. Therefore, the development of scale-aware cumulus cloud parameterisation schemes is one of the development trends of numerical model refinement. By introducing the scale-aware KFeta (Kain-Fritsch eta) convective parameterisation scheme into the CMA-MESO (China Meteorological Administration Mesoscale model) model, the paper combines three resolutions (1 km, 3 km, and 10 km) and designs three sets of experiments so that a numerical simulation test is carried out on a precipitation process on 11-12 July 2023, in the mountainous area of southwest China, and a 7-day batch test is carried out on the precipitation process on 17-23 June 2023. This is done to test and evaluate the effect of the scale adaptation scheme on precipitation simulation in the southwest mountainous area. The results show that: (1) In the case experiment, the scale adaptation scheme has a good grasp of the precipitation rain band and precipitation intensity, and the simulation of the heavy precipitation centre has certain advantages. With the increase in resolution, the precipitation intensity and falling area of the scale adaptation group are closer to reality, which greatly reduces the false precipitation caused by cumulus clouds and increases the grid precipitation. (2) The combined reflectance factor and vertical velocity simulation results in the strong convection region of the scale adaptation scheme are better. (3) In the batch test, the scale adaptation scheme has a good and stable simulation ability for precipitation in the southwest mountain area, especially the simulation results of the scale adaptation scheme for moderate rain and above, which are more advantageous, and the precipitation TS score of the original scheme improves by 4% overall. In general, the scale adaptation scheme performs well in the forecast of heavy precipitation in the southwest mountainous area, providing a basis for improving the current numerical model of heavy precipitation forecasts.
    2025,53(4):520-534, DOI: 10.19517/j.1671-6345.20240361
    Abstract:
    This study utilises best-track datasets of tropical cyclones (TCs) from the Joint Typhoon Warning Center (JTWC), Japan Meteorological Agency Tokyo Regional Specialised Meteorological Center (RSMC), and Shanghai Typhoon Institute of China Meteorological Administration (CMA), along with NCEP reanalysis data and correlation analysis methods, to investigate the fundamental characteristics of TC intensity and frequency in different seasons (July-September for summer and October-November for autumn) and subregions over the Western North Pacific (WNP) during 1989-2020, as well as their relationships with local environmental factors. The results indicate that: (1) The total TC frequency observed in the three summer WNP subregions (Area I: 10°-25°N, 110°-145°E; Area II: 10°-25°N, 145°E-180°; Area III: 25°-37.5°N, 125°E-180°) is 10164, while the total TC frequency in the three autumn subregions (Area I: 5°-17.5°N, 110°E-180°; Area II: 17.5°-35°N, 142.5°E-180°; Area III: 17.5°-35°N, 120°-142.5°E) is 4984. This demonstrates significantly higher TC activity in summer than in autumn. (2) TC activity during both summer and autumn exhibits statistically significant correlations with 850 hPa relative vorticity (RVOR), except for Area II in autumn. In addition to low-level RVOR, summer TC frequency in Area I is associated with 500 hPa vertical velocity (OMEGA) and 700-500 hPa relative humidity (RHUM). Summer TC intensity in Area II is linked to 700-500 hPa RHUM, 500 hPa OMEGA, and vertical wind shear (VWS), while summer TC frequency in Area II correlates with 500 hPa OMEGA and VWS. Autumn TC frequency in Area I shows a relationship with 500 hPa OMEGA. Regardless of season, TC activity generally displays either nonsignificant correlations or significantly negative correlations with oceanic factors. The local environmental factors influencing TC activity vary across regions and seasons, depending on seasonal and regional divisions, which indicates complex interactions. (3) A strong monsoon trough enhances TC activity in summer and autumn Area I through low-level high RVOR, mid-level ascending motion, and high humidity. The warming of sea surface temperature in the Nino3.4 region can induce anomalous westerly winds at 850 hPa in Area II during summer, leading to increased low-level RVOR. Concurrently, an anomalous anticyclonic circulation emerges at 200 hPa, resulting in reduced VWS. The combination of the enhanced low-level RVOR and upper-level anticyclonic circulation further strengthens mid-level upward motion and moisture convergence, thereby influencing TC activity in this region. When the Western Pacific subtropical high extends westward (retreats eastward), it generates localised negative (positive) vorticity anomalies, leading to reduced (increased) TC frequency entering summer Area III. Strengthened mid-level steering flows further enhance the intrusion of intense TCs into this region. The convergence in the relative low region between two highs enhances low-level RVOR, which consequently modulates TC activity in Area III during autumn.
    2025,53(4):535-544, DOI: 10.19517/j.1671-6345.20240350
    Abstract:
    The study of intraseasonal oscillation (ISO) characteristics is crucial for both understanding internal variability and improving prediction skill at the sub-seasonal time scale. Based on daily precipitation from 108 national meteorological stations across Shanxi and NCEP/NCAR daily atmospheric reanalysis datasets spanning 1980 to 2022, this study investigates the climatological spatiotemporal evolution of summer precipitation ISO in Shanxi and its association with atmospheric circulation by using statistical methods of Lanczos filtering, power spectrum analysis, and composite analysis. The main findings are as follows: (1) Summer precipitation in Shanxi shows a significant 10-50-day ISO signal. The intensity of the precipitation ISO displays a significant and positive correlation with precipitation, with a high temporal correlation value of 0.88 and a consistent increasing trend after 2000. Specifically, precipitation increases at a rate of 35.4 mm/decade, while ISO intensity increases by 0.27 (mm·d-1)/decade. Spatially, areas with higher precipitation generally experience stronger ISO, and the most active ISO centres are located in southern Shanxi and the mountainous areas. (2) Two typical summer precipitation ISO cycles in Shanxi exhibit three-stage evolution according to their composite analysis. The initial stage is characterised by a weakening of drought conditions and the onset of positive precipitation anomalies in parts of Shanxi; the active stage features the expansion and intensification of positive precipitation anomalies until peak precipitation progresses southward to southern Shanxi; and the weakening stage begins when ISO-induced positive precipitation anomalies retreat and terminates when the negative precipitation anomalies re-emerge over most parts of Shanxi. (3) The evolution of precipitation ISO is closely linked to vertically integrated water vapour transport. The enhancement (weakening) and westward-northward (eastward-southward) shift of low-frequency anticyclonic water vapour transport over the subtropical western Pacific plays a vital role in regulating the ISO precipitation cycle. During the dry phase, the water vapour transport is too weak to reach Shanxi. As the anomalous anticyclone shifts westward and northward, the ISO enters its active stage, accompanied by strengthened and persistent southeasterly water vapour transport, placing Shanxi in a water vapour convergence zone. As this transport weakens and retreats eastward, the water vapour convergence zone gradually shifts out of Shanxi. After the weakening stage, a new ISO cycle restarts. This study elucidates the climatological spatiotemporal evolution of summer precipitation ISO in Shanxi and its synergistic interaction with atmospheric circulation, providing a scientific foundation for regional sub-seasonal precipitation forecasting and offering new insights into the ISO characteristics and mechanisms over mid-latitude regions with complex terrain.
    2025,53(4):545-556, DOI: 10.19517/j.1671-6345.20250023
    Abstract:
    Based on the National Basic Meteorological Station observation data, European Centre for Medium-Range Weather Forecasts Reanalysis, and the typhoon best track data of Shanghai Typhoon Research Institute from 1951 to 2022, the characteristics of daily extreme rainfall events caused by typhoons and the points of daily extreme rainfall forecast in Wenzhou are studied and analysed using the percentile method and composite analysis. The results show that typhoons causing daily extreme rainfall in Wenzhou are all landing typhoons. Daily extreme rainfall is concentrated between July and October, with the most occurring in August and the strongest in September. According to similar rainfall patterns and paths, they are divided into four types: Southern Zhejiang, Eastern Guangdong, Middle, and Southwest types. The heavy rainfall centres of the Southern Zhejiang type and Eastern Guangdong type are located in the northeast of Wenzhou, and the corresponding typhoons land in the south of Zhejiang Province and the east of Guangdong Province, respectively. The heavy rainfall centre of the Middle type is located in the middle of Wenzhou, and the corresponding typhoons land in the area from the junction of Zhejiang and Fujian Provinces to the middle of Fujian Province. The heavy rainfall centre of the Southwest type is located in the southwest of Wenzhou, and the corresponding typhoons land in the middle and south of Fujian Province. Except for the Eastern Guangdong type, low-layer vorticity at 850 hPa reaches 8×10-5/s or above, which provides a good indication for daily extreme rainfall forecasts. The intensity differences of water vapour transport, water vapour convergence, vertical water vapour flux gradient between 850-925 hPa, and different types of low-layer jets correspond well with the intensity of extreme rainfall. The differences between the west boundary of the water vapour transport above 30 g/(s·hPa·cm) and the position of the strong water vapour convergence centre below -(2-4)×10-6 g/(cm2·hPa·s) correspond to the differences in extreme rainfall areas. The dense zone of water vapour flux and the convergence centre of water vapour flux at 925 hPa correspond well with the area of heavy rainfall, except for the Eastern Guangdong type. The differences in the development height and intensity of vertical ascending motion below -0.8 Pa/s correspond to the differences in extreme rainfall area and intensity. The characteristics of the low-layer convergence zone explain the distribution of vertical ascending motion. The uplift caused by sea-land terrain in the east and mountainous terrain in the west strengthens the ascending motion. The intensity difference of differential pseudo-equivalent potential temperature advection in the middle and lower levels corresponds with the difference in rainfall intensity. Cold air has a certain enhancement effect on the extreme rainfall events of the Eastern Guangdong, Middle and Southwest types.
    2025,53(4):557-571, DOI: 10.19517/j.1671-6345.20240265
    Abstract:
    Convection initiation (CI) directly affects the early warning of severe convective weather, while the mechanism of CI with obvious regional characteristics is complex. Based on multi-source high-resolution observation data and ERA5 reanalysis data, the characteristics and causes of the extreme severe convection triggered at the trumpet-shaped terrain in the eastern foot of the Taihang Mountains on 17 May 2023 are explored, combined with a similar case. The results show that under the unstable stratification of the 500 hPa shallow trough carrying weak cold air from the middle layer invading the surface thermal low pressure, the extreme convection caused by a supercell storm evolved from a mesoscale convective cell triggered at the 400 m height of the trumpet-shaped terrain in the eastern foot of the Taihang Mountains. Under the environment of continuous high temperature and weak vertical wind shear, a convective cell was triggered near Wangkuai Reservoir on the warm side of the temperature front below 850 hPa. The 2-m temperature difference between the north and south sides of the convective cell was 3-4 ℃, and the water vapour was close to saturation. Meanwhile, the convergence line of southeast wind and northerly wind extended from the ground to 850 hPa, and the thickness of easterly wind with a maximum wind speed of 6-8 m/s near 0.5 km was about 1 km. Before convection initiation, the new banded convective cumulus clouds at the 200-600 m slope of the eastern foot of the Taihang Mountains were consistent with the mountain direction, which was related to the boundary convergence line and the thermal forcing on the mountain. The convection was triggered on the side of the convergence line near the mountain. Froude number (Fr) , terrain vorticity and terrain divergence quantitatively characterised the terrain uplift effect. The Fr number decreased from the mountain to the plain with the peak value at the height of 400 m where the convective cell was triggered. Before CI, the Fr number escalated to about 1, indicating the airflow climbing effect, and the cyclonic terrain vorticity and terrain horizontal divergence were enhanced, then the convective cell was triggered.
    2025,53(4):572-584, DOI: 10.19517/j.1671-6345.20240281
    Abstract:
    From June 26 to 28, 2022, a regional heavy rainfall event occurred in Shandong Province, characterised by significant precipitation intensity and extensive spatial coverage. This event ranks among the most severe heavy rainfall processes that induce disasters in recent years. The precipitation process is divided into three distinct stages, with warm-sector precipitation driven by a low vortex and low-level jet playing a dominant role in this heavy rainstorm. The instability mechanisms of warm-sector precipitation, as well as the triggering and maintenance of heavy precipitation, present significant challenges for operational forecasting and are the primary focus of this study. Based on conventional surface and upper-air meteorological observation data, ERA5 hourly reanalysis data, and radar data, this study analyses the water vapour conditions, atmospheric instability, and frontogenetic characteristics of this heavy rainfall event. The results indicate that the precipitation process in the warm sector of the low vortex primarily occurred within the low-level jet zone south of the warm shear region of the low vortex. The low-level jet provided ample water vapour conditions for precipitation, while a region of strong water vapour flux convergence north of the jet stream served as an effective indicator for heavy precipitation. At the onset of precipitation in the warm vortex region, strong convective instability was observed in the mid-to-lower troposphere, with upward motion initiated by the release of convective instability, exhibiting vertical convection characteristics. During the peak precipitation period, the ascending motion was influenced by both convective instability and symmetric instability, with symmetric instability being predominant, resulting in a combination of vertical and oblique convective processes. This precipitation process was accompanied by pronounced frontogenesis, featuring strong geostrophic wind deviation convergence in the frontogenesis region, which supplied essential dynamic uplift conditions for precipitation initiation and intensification. Analysis of the deformation term and divergence term in the frontogenesis function reveals that the divergence term was the main factor of frontogenesis in this process. Low-level convergence not only provided dynamic conditions for precipitation initiation but also integrated radar precipitation echoes with mesoscale convergence lines at the surface, influencing the morphology of cumulus precipitation echoes and forming mesoscale convective rainbands aligned along the guiding airflow. The mesoscale convective rainband moved along the guiding airflow, creating a “train effect” that resulted in heavy precipitation. These findings enhance operational forecasting capabilities for warm-sector precipitation associated with low vortices and similar processes, providing valuable insights for forecasters to develop systematic models of warm-sector precipitation weather systems.
    2025,53(4):585-594, DOI: 10.19517/j.1671-6345.20240276
    Abstract:
    Based on the observation data of Shenyang X-band dual-polarisation phased-array radars (XPAR-D) and S-band radar (CINRAD/SC), combined with minutely precipitation data collected by automatic meteorological stations in Shenyang, this paper analyses the characteristics of a short-time heavy rainfall process that occurred in Shenyang on September 18, 2023. The results are as follows. The comparative observation results of XPAR-D were more detailed. However, its detection capability for weak radar echoes and those that were far away from the radar were weaker than that of the SC radar. The comparative observation results show that the SC radar had a larger coverage area and a more complete structure than XPAR-D. In the area with less influence of electromagnetic attenuation, the detection capabilities of the XPAR-D and SC radar in terms of the structure and intensity of the reflectivity factor and radial velocity were basically comparable. The area of strong echoes of the XPAR-D was wider, while the area of the region with high wind speed of the SC radar was larger. The rapid development and maintenance of the relatively strong echoes of XPAR-D, the relatively large values of CR and ZDR, as well as the sharp increase and maintenance of the KDP value jointly contributed to the occurrence of this short-time heavy rainfall. Before the precipitation started, the detection results of XPAR-D often showed large values of ZDR. The rapid increase of CR and the abnormally high value of ZDR had good indicative significance for the onset of precipitation. After the onset of the short-time heavy rainfall, there was a good corresponding relationship between CR and ZDR, which effectively indicated the duration and variation trend of the heavy precipitation. The sharp increase of KDP served as a warning for high values of minute precipitation, and the value of KDP more intuitively reflected the intensity of minute precipitation. During this short-time heavy rainfall process, the ZDR column in the XPAR-D observation results was located on the left side of the updraft of the convective cell, which corresponded well to the location of the weak echo area, and there was a separation phenomenon between the ZDR column and the KDP column. The high-value band of KDP value corresponded to the strong echo centre of the convective cell, and the KDP column corresponded to the heavy precipitation centre on the ground. Although the radial velocity results detected by XPAR-D during this short-time heavy rainfall event didn’t meet the criteria for a mesocyclone, they indicated that weak eddies also had the potential to enhance precipitation.
    2025,53(4):595-605, DOI: 10.19517/j.1671-6345.20240337
    Abstract:
    Lightning, as one of the frequent natural disasters in China, poses significant meteorological hazards. Weather radar systems, with their inherent advantages of high spatiotemporal resolution, enable precise characterisation of lightning formation mechanisms and evolutionary patterns through synergistic integration with lightning detection datasets. This paper analyses lightning forecasting and early warning services in the eastern and western regions of China, using Shanghai and Kashgar as representatives. By leveraging multi-source observations, including lightning locators, weather radar mosaic products, and sounding data, an annual statistical analysis of the spatiotemporal distribution, three-dimensional characteristics of lightning, and their corresponding radar signatures is conducted in these two regions. The study explores the causes of the differences in lightning characteristics between the eastern and western regions. The results indicate that: (1) Both Shanghai and Kashgar exhibit concentrated lightning activity between May and September, with peak occurrences from afternoon to evening. Notably, Kashgar demonstrates distinct nocturnal characteristics in lightning distribution due to topographic effects. Geospatial analysis reveals contrasting spatial patterns: Shanghai’s lightning hotspots predominantly cluster over urbanised areas and land-water interfaces, whereas Kashgar’s lightning distribution shows strong orographic correlation, with maximum density zones located along the southern foothills of the Western Tianshan Mountains, eastern flanks of the Pamir Plateau, and northern slopes of the Kunlun Mountains. Statistically, the average lightning stroke density in Shanghai significantly surpasses that in Kashgar, maintaining a ratio of approximately 732.1∶1. (2) The combined reflectivity factor intensity, echo top height, and vertical liquid water content associated with lightning echo cells in Shanghai are markedly greater than those observed in Kashgar. The extension height of lightning echo cells in Shanghai is substantially higher than that in Kashgar. Notably, the 30 dBz, 35 dBz, and 40 dBz echo exceeding the -20 ℃, -10 ℃, and 0 ℃ layer height serves as a crucial indicator for lightning forecasting and early warning in Shanghai, whereas for Kashgar, the echo top height surpassing the -10 ℃ layer and the 30 dBz echo reaching the 0 ℃ layer hold greater predictive value. (3) Lightning activity is formed under the combined effects of three essential factors: sufficient atmospheric instability energy, dynamic lifting mechanisms, and adequate moisture supply. Comparative analysis reveals that during thunderstorm days, Shanghai exhibits significantly higher values of Most Unstable CAPE (MUCAPE), mid-level Relative Humidity (midRH), and Precipitable Water (PW) compared to Kashgar, while demonstrating lower Most Unstable Lifted Index (MULI) values. These meteorological parameters indicate stronger convective activity in Shanghai, where intense updrafts transport abundant moisture to upper colder layers. This enhanced vertical transport mechanism creates more favourable conditions for charge separation processes, making Shanghai more prone to lightning activity than Kashgar.
    2025,53(4):606-616, DOI: 10.19517/j.1671-6345.20240270
    Abstract:
    Based on the precipitation data from meteorological stations along the Baomao Expressway in Xiangxi Prefecture from 2016 to 2023, this study conducts a comprehensive analysis of the temporal and spatial distribution characteristics of precipitation along the expressway, including annual and monthly characteristics, various levels of precipitation characteristics, short-term heavy precipitation characteristics, continuous precipitation characteristics, and diurnal variation characteristics. By integrating precipitation data, geographic information data, and road data, an evaluation index system for the risk level of slope failures along the expressway is established from three aspects: precipitation factors, terrain environment factors, and road factors. The slope failure risk level zoning research of the Baomao Expressway in Xiangxi Prefecture is carried out using the Analytic Hierarchy Process (AHP) and the Natural Breakpoint Method. The results show that: (1) The annual average precipitation along the expressway shows a spatial distribution pattern of higher precipitation in the south and lower in the north. In 2020, precipitation is abundant, while in 2022 and 2023, precipitation is scarce. Precipitation mainly occurs from April to September, with an average monthly precipitation exceeding 140 mm, and the highest precipitation is in June, reaching 236 mm. (2) The average number of days with rainstorm and above precipitation at each station along the expressway is 4.5 days, with an average intensity of 77.7 mm/d. Short-term heavy precipitation shows significant differences in distribution, with the maximum being 80 mm/h and the minimum being 46 mm/h. The total frequency of continuous precipitation is the highest at GS56-2 (Longjingao) with 31 times, and the lowest at GS56-7 (Fenghuang) with less than one time per year. The peak precipitation occurs in the afternoon and after dusk, and the night rain feature is obvious. (3) The risk level of slope failures along the expressway is divided into four grades: high, relatively high, medium, and low. The overall risk shows a characteristic of being higher in the north than in the south. The high-risk and relatively high-risk areas of slope failures are distributed in sections such as Biancheng, Longjingao, Maliuchang, and Jixin. The low-risk areas are located near the Jishou Station and the Fenghuang Station. For high-risk and relatively high-risk areas, in terms of disaster prevention and mitigation, measures such as reinforcing the slope and taking drainage measures should be taken, and monitoring and early warning should be strengthened. The results of this study have certain guiding significance for the prevention of slope failure disasters along the Baomao Expressway in Xiangxi Prefecture.
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    2020,48(6):917-922, DOI:
    [Abstract] (1054) [HTML] (0) [PDF 1.07 M] (65593)
    Abstract:
    Using the meteorological observation data of Yuepuhu in Xinjiang from 1981 to 2019, combined with the growth and development of Flos Lonicerae, the relationship between the climatic conditions and the growth of Flos Lonicerae in Yuepuhu are analyzed. According to the ecological characteristics of Flos Lonicerae, the meteorological conditions of Flos Lonicerae cultivation in Yuepuhu are systematically analyzed, and the results show that the average temperature of each phenological stage of Flos Lonicerae in Yuepuhu show an obvious increasing trend; the number of sunshine hours has an obvious increasing trend; and the water source is sufficient. These are conducive to the normal growth and development of Flos Lonicerae. As the temperature rises and the number of sunshine hours increases, the planting time has been advanced from the previous mid March to early March; the planting area has expanded year by year, from tens of hectares in 2016 to 345 hm2 in 2019; and the planting mode has been adjusted from the plain cropping to inter cropping method. In the inter planting mode, the varieties are unified with Beihua No.1. The number of consecutive high temperature days of ≥38 ℃ during the growth and development of Flos Lonicerae, especially in ≥40 ℃ high temperature weather, the short term heavy precipitation weather, windy and sandy weather and other meteorological conditions have certain influence on the quality and yield of Flos Lonicerae. Exploration of the favorable climatic conditions for the development of the Flos Lonicerae planting industry in Yuepuhu provides a scientific basis for the construction of the Yuepuhu Flos Lonicerae industrial base, as well as the meteorological guarantee for the increase of income of flower farmers.
    2021,49(1):55-62, DOI:
    [Abstract] (1007) [HTML] (0) [PDF 11.58 M] (64693)
    Abstract:
    Clouds are an important part of the earth system, which can affect the radiation balance of the earth atmosphere system by affecting atmospheric radiation transmission. At present, the information obtained from three dimensional cloud observation has certain limitations, so it is necessary to obtain more accurate three dimensional cloud information by using multi source observation data merging analysis. Based on the successive correction method, 〖JP2〗the Three Dimensional Cloud Merge Analysis Operation System (3DCloudA V1.0) integrates multi source data such as numerical forecast products, geostationary meteorological satellite observation, meteorological radar observation to produce the real time 0.05°/h three dimensional cloud merging analysis product covering China and its surrounding areas (0°-60°N, 70°-140°E), which is distributed to the national and provincial meteorological departments through the China Telecommunication System. The modular system framework is considered in the operation system design and construction process, and the fault tolerant functions such as EC Flow scheduling process real time monitoring and automatic restarting are developed, which effectively improves the stability and reliability of the operation system. Evaluations show that through merging multi source observation data, the three dimensional cloud merge analysis product can describe cloud the top, inside and bottom information more accurately.〖JP〗
    2014,42(5):823-831, DOI:
    [Abstract] (1770) [HTML] (0) [PDF 2.17 M] (61634)
    Abstract:
    In order to improve the weather forecast quality over the low latitude plateau regions, the wind data retrieved with VAD (Velocity Azimuth Display) method are assimilated to the WRF (Weather Research and Forecasting) model by WRF 3DVar (3 Dimensional Variational Data Assimilation System). With different assimilation schemes, a torrential rain event occurred in Yunnan Province from 00:00UTC 30 June 2009 to 00:00UTC 1 July 2009 is numerically simulated and comparatively analyzed. The results indicate that the initial wind fields of the WRF model are markedly improved by assimilating the retrieved wind data. The WRF 3DVar can availably introduce the information of the retrieved wind to the initial conditions of the regional numerical model. The assimilation of the retrieved wind data helps enhance the wind convergence and vapor transportation over the rainy area. Furthermore, the assimilation help improve quantitative precipitation forecasts. The quantitative test of the 18 hour rainfall forecast shows that forecasts are more accurate, less pretermissions, and more rational pertinence for over 250 mm precipitation in the assimilation experimentations. The higher the assimilation frequency and the longer the assimilation time is, the more obvious the influence of data assimilation on the initial fields and forecast fields of the regional model is. But long assimilation time may increase the speed of synoptic systems and the overestimate rainfall, and so the suitable selection of frequency and time is crucial in numerical experimentations.
    2013,41(4):758-763, DOI:
    [Abstract] (2123) [HTML] (0) [PDF 26.87 M] (61366)
    Abstract:
    Through investigating the lightning disasters of ancient buildings, the distribution of ancient buildings being stricken by lightning are analyzed. It is found that animal finials and prominent parts of the like, old trees, towers and kiosks, service facilities and other parts of ancient buildings are vulnerable to lightning strikes. It is found that once an ancient building is stricken by lightning, it is probable to be stricken again by lightning. The reasons for that ancient buildings are stricken and caught fire by lightning are analyzed, and the proportions of casualties caused by ancient building lightning disasters are calculated. It is concluded that the reasons for ancient buildings stricken by lightning includes the appropriate location and structure of ancient buildings, tree triggering, internal environment changes, and water infiltration because of disrepair and other factors vulnerable to lightning.
    2017,45(6):1116-1124, DOI:
    [Abstract] (1324) [HTML] (0) [PDF 2.65 M] (50152)
    Abstract:
    Data quality assessment is an important part in model operation application. In this paper, the soil moisture observation data and China Meteorological Administration Land Data Assimilation System (CLDAS) data are used to establish the online CLDAS data quality assessment system through the MySQL database and the Web technology like html, JavaScript, HighChart， etc. The assessment analysis between the simulated soil moisture and the observed soil moisture at any of stations and provinces, times and different soil layers is implemented in the form of correlation coefficient, root mean square error, relative deviation, and mean deviation. Diagrams such as time series and scatter are visually displayed to compare the observation and simulated data in the system. The statistical indexes can be calculated immediately using JavaScript language in the Web platform. The assessment results and the comparison diagrams can be showed through the internet Web page, and the real time monitoring of the model product data quality can be achieved.
    2013,41(1):15-19, DOI:
    [Abstract] (2615) [HTML] (0) [PDF 12.84 M] (31620)
    Abstract:
    Due to the influence of the curve Earth, the fixed detection mode of the CINRAD/SA weather radar uses the minimum elevation angle of 0.5 °, so the blind area is relatively big, and the detection capability for low level precipitation echoes is limited. On the basis of experiments, the calculation formulas of the minimum height applicable when CINRAD/SA detects with positive and negative elevation angles are devised. Then the minimum detecting heights of CINRAD/SA at different distances with different elevation angles (0.5°, 0°, -0.3°,-0.5°) are calculated. Through analyzing characteristics of radar products detected under different elevation angles, some suggestions on CINRAD/SA about using negative elevation angles are presented.
    2010,38(3):289-294, DOI:
    [Abstract] (2803) [HTML] (0) [PDF 63.01 M] (30470)
    Abstract:
    With the intensive observation data and NCEP/NCAR reanalyzed data, an unusual heavy fog process occurred over the east central China from 25 to 27 December in 2006 is analyzed in aspects of the large scale synoptic condition and dynamic and thermodynamic mechanisms. It was shown that the fog occurred while the near ground wind velocity varied from 0.3 to 2.9 m/s and the dense fog occurred while the wind velocity varied from 0.3 to 2.4 m/s and the visibility was within 15 meters when velocity was from 0.8 to 1.1 m/s. Although vapor condition was bad and rainfall didn’t occur within a few days before the heavy fog, the continuous vapor transportation of the southwestern air current before a trough offered plentiful vapor for the fog. The results also show that the stable stratification gradually established before the fog.At first, the instable stratification built at higher levels after sunrise, subsequently passed downward to lower levels, and then the inversion layer destroyed and the fog dispersed and cleared off. The results indicate that the visibility changed rapidly and violently before the first stage of the severe heavy fog but it did not before the second stage.
    2010,38(3):281-288, DOI:
    [Abstract] (2359) [HTML] (0) [PDF 57.54 M] (29369)
    Abstract:
    In order to reveal the development mechanisms of heavy snowfall in Hebei Province,two heave snow processes on 14 to 16 March 2003 and 20 to 21 February 2004 are selected. A contrast analysis of their meteorological characteristics is made from aspect of synoptic situation and physical mechanism by means of numerical diagnosis with the NCEP reanalysis data and conventional observation data. The results show that the combination of south and north troughs with identical phase around 110°E at 500 hPa, the allocation of the surface pressure field with high in north and low in south, and the appearance of the ground inverted trough in the Hetao area of NW China, as well as the thermodynamic conditions with warm temperature tongue and warm advection in the lower troposphere, are the favorable large scale background for the formation of heavy snowfall. There are three important paths of water vapor in the two snow events: from southwest in front of the 500 hPa trough, from east at low level, and from low level jet. From the cross sections of vorticity, divergence, vertical velocity and vertical helicity, it is found that the vertical distribution of convergence at low level but divergence at upper level and ascending motion in the whole troposphere benefit the forming and maintaining of heavy snowfall, and the distribution of positive vorticity (vertical helicity) in the whole troposphere is most favorable. It is also suggested the temperature descending to below 0 ℃ at both 850 hPa and 925 hPa, meanwhile below 1 ℃ in the surface, is favorable to snowing. The results can be used as reference in the forecasting heavy snowfall.
    2010,38(4):432-436, DOI:
    [Abstract] (2260) [HTML] (0) [PDF 13.24 M] (24713)
    Abstract:
    A whole province range thunderstorm occurred in Zhejiang Province on 26 June 2009, and the occurrence frequency of cloud to ground lightning in this thunderstorm is the highest since the establishment of the lightning position system in 2006. By means of the observation data from the lightning position system, the intensive rainfall observation system, and Doppler radar, the characteristics of the cloud to ground lightning process are analyzed. The results indicate that lightning strokes were mainly negative; in the lightning echo image, negative strokes were mostly distributed in the area of 25 dBz to 55 dBz, and positive strokes were usually in the area of 25 dBz to 35 dBz; lightning strokes occurred mostly on the side of echo development or advancement, distributed around the area with maximum gradients, and there seldom appeared lightning strokes around a strong echo center; the frequency of cloud to ground lightning was correlated closely with the accumulated precipitation of the whole province during the thunderstorm. The peak value of precipitation lagged more than 0.5 hour behind the peak value of the frequency of cloud to ground lightning, and the accumulated precipitation of the whole province occurred 1 to 2 hours behind the peak value of the frequency of cloud to ground lightning. Therefore, the cloud to ground lightning data can be used as a basis in short range severe precipitation forecasting.
    2009,37(1):67-73, DOI:
    [Abstract] (2802) [HTML] (0) [PDF 788.79 K] (22883)
    Abstract:
    Soil moisture is a key variable in water and energy exchanges in land atmosphere interface. The passive microwave remote sensing is the most potent technology to retrieve soil moisture. A brief introduction is made to microwave theory, and a general review of soil moisture retrieval algorithms is given. Three typical cases are illustrated based on the different microwave sensors by comparing various algorithms, which correspond to the three parameter AMSR based retrieval developed by Njoku and Li, the two parameter SMMR based retrieval developed by Owe et al. and the two parameter SSM/I based retrieval developed by Wen et al. The insufficiency and potentials in the researches on soil moisture are discussed.
    2024,52(3):318-329, DOI: 10.19517/j.1671-6345.20230129
    [Abstract] (204) [HTML] (0) [PDF 75.13 M] (19614)
    Abstract:
    By introducing the relief shading method, which is often used in making the topographic maps, into the visualisation of numerical weather forecast data, this article presents the achievement in three-dimensional drawing of meteorological variables, such as air pressure and geopotential height. Based on the principle and implementation of hill shading, which uses the relationship between the illumination angle, the direction, the slope, and the orientation of the terrain to calculate the brightness value of luminous flux, the relief shading method makes use of the brightness value to display the three-dimensional sense of meteorological model data. At the same height, the steeper the terrain, the darker (brighter) the shaded (sunny) side; under the same slope, the higher the terrain, the darker (brighter) the shaded (sunny) side, which is consistent with the real-life visual effect. The colouring method of the shaded relief map is to use the brightness value (V) in the HSV colour space which is calculated on each grid point, combined with hue (H) and saturation (S) to obtain a complete HSV colour scheme. Through the conversion from the HSV colour space to the RGB colour space, the latter colour space is used for drawing a coloured shaded relief map for meteorological model data. In the shaded relief map, the high-pressure centre in the weather system is often shown as a raised peak, and the low pressure is shown as a depressed valley; a large pressure gradient can be seen as a steep slope, while a small pressure gradient can be seen as a gentle slope. Compared with the traditional isoline and colour filling analysis, it is found that the shaded relief map can help to identify high-low weather systems by concave-convex shapes and reflects the gradient changes of weather systems through the steepness of slope, thus intuitively representing the three-dimensional distribution of atmospheric circulation. In addition, the shaded relief map has the ability to visualise model data in pixel level details, identify early eddy current disturbances in small gradients, and reveal equivalent terrain effects, which helps the meteorologists better interpret the model data and provides the references for the improvements of data process functions in numerical models. Furthermore, the relief shading method is suitable for using the synthetic animations to showcase the fluid characteristics of atmospheric motion, which is conducive to popularising the concept of various weather systems, such as the high, the low, the trough and ridge, and their evolution to the public.
    2024,52(3):403-414, DOI: 10.19517/j.1671-6345.20230186
    [Abstract] (293) [HTML] (0) [PDF 25.35 M] (19613)
    Abstract:
    Based on the hourly and daily precipitation data of 61 national meteorological stations from 1961 to 2020 and 998 regional automatic meteorological observation stations from the beginning of the establishment to 2020 in Liaoning Province, we analyse the main causing factors of rainstorm and flood disaster, calculate the environmental indicators of rainstorm and flood disaster, and complete the hazard assessment of rainstorm and flood disaster in Liaoning Province. The results show that the high-risk area of rainstorms and floods is mainly located in Dandong. The high population risk areas of rainstorm and flood disaster are mainly located in Shenyang and Dalian urban areas. The high economic risk areas of rainstorm and flood disaster are mainly located in Dalian and Panjin urban areas. The high-risk areas of rice and maize are mainly located in Jinzhou, Panjin, and Dandong. The disaster risk of the rainstorm process on 28-29 July 2022 is pre-assessed using the intelligent grid forecast data of Liaoning Province. It is found that the high hazardous areas are mainly distributed in Chaoyang, Huludao, and the central part of Liaoning. The population and economic high-risk areas caused by the rainstorm disaster are mainly located in the western and central areas. The high-risk areas of rice and maize caused by rainstorm disaster are mainly located in Shenyang, Tieling, and the north of Chaoyang. It is estimated that the population affected in the high-risk area is about 4.49 million, the economic loss is about 14.32 million yuan. The affected rice area is about 10,280 hectares, the maize area is about 17,798 hectares. Through the post-disaster effect test, it is found that the pre-assessment model is effective and can be used in the actual rainstorm and flood disaster risk assessment business.
    2024,52(3):446-455, DOI: 10.19517/j.1671-6345.20230140
    [Abstract] (239) [HTML] (0) [PDF 17.35 M] (19608)
    Abstract:
    Under the common influence of factors including complex terrain, subtropical high pressure, and monsoon weather, the wind field in the alpine canyon areas of is complex and changeable, and it is easy to form the “narrow pipe effect”, which leads to disastrous gales that have a great impact on the construction and operation of large-scale projects. In this paper, based on Fluent, a fluid dynamics computing software, a standard turbulence model and PISO algorithm are used to study the variation of wind velocity field near the dam during dam construction and the influence of dam construction on the wind velocity field, taking the level 7 north wind in Baihetan Hydropower Station as a typical calculation condition. The research results show that the blocking effect of the dam body makes the wind velocity field at the top of the dam generate flow separation and wind field uplift, and a low wind velocity zone forms below the dam elevation. When the dam elevation is 650 m and 750 m, the wind speed within the cable platform is about 15 m/s to 16 m/s, and the channel length of the significant influence area by the wind speed vertical distribution downstream of the dam is 4.4 Ht and 4.5 Ht (Ht being the dam height). The significant influence heights of the wind velocity field at the top of the dam are 2.0 Ht and 3.0 Ht respectively. When the dam is filled to the normal water level of 825 m, the channel length of the significant influence area by the wind field downstream of the dam is 8.0 times the dam height (2.3 km), and the maximum influence channel length is 30.4 times the dam height (8.8 km). The influence height of the dam top reaches about 1500 m height, which is 3.5 times the dam height.
    2024,52(3):347-355, DOI: 10.19517/j.1671-6345.20230189
    [Abstract] (299) [HTML] (0) [PDF 11.03 M] (19583)
    Abstract:
    In order to expand the space of meteorological business, integrate multiple fields of monitoring, and promote the development of the meteorological industry towards efficiency, convenience, and intensification, the Guizhou Province Meteorological Comprehensive Monitoring System APP is developed using mainstream mobile apps as carriers, based on the Springboot+Vue+Mybatis Plus development framework, and using multi-platform compatible development (uni-app), real-time capture of change data (FlinkCDC), and an efficient packaging framework (Mybatis-Plus) among other technical means. The article provides a detailed introduction to the framework structure and functional design adopted by the APP as an independent monitoring system, as well as the big data development technology and its business advantages involved. At the technical level, the system utilises uni-app development technology to make the APP client more compatible and can simultaneously adapt to various application platforms such as iOS, Android, Web, and various mini-programs; using Mybatis-Plus as the database driver framework to improve code reusability and reduce database performance overhead; by using FlinkCDC as a data processing and incremental synchronisation tool, resource waste caused by full data synchronisation can be avoided, simultaneously serving as a one-way synchronisation tool to enhance the security of meteorological data. At the framework level, in order to avoid security risks caused by network mixing, the system introduces a Demilitarised Zone (DMZ) to isolate the internal and external network data environments. The internal network department is responsible for collecting and storing meteorological data from various formats such as databases, static files, API interfaces, logs, etc. Then, it will be synchronised unidirectionally with the external network environment through FlinkCDC. The external network interacts with the mobile APP by receiving data pushed by FlinkCDC. The software is aimed at meteorological users at all levels of province, city, county, and station. Through preliminary research and analysis, four functional modules have been developed for different users, including regional automatic stations, weather radar stations, network connectivity, and interface service status. This provides convenience for meteorological data monitoring and equipment maintenance, and improves the timeliness of response. The system has been put into use throughout the province since 2022. The application results show that the APP adapts to multiple mobile system platforms such as Android and iOS, and has a friendly interface, simple operation, and stable operation. Since its application, the timeliness of meteorological data has improved, enriching the monitoring business methods of Guizhou Province, meeting the user needs at all levels, and playing a positive role in the development of the meteorological industry.
    2024,52(3):380-391, DOI: 10.19517/j.1671-6345.20230246
    [Abstract] (239) [HTML] (0) [PDF 14.80 M] (19579)
    Abstract:
    Flash heavy rain and the resulting low visibility make it difficult for pilots to visually assess the runway clearly, severely impacting the take-off and landing of aircraft, thereby posing a threat to aviation operational safety. Moreover, the flight delays and diversions caused by this also result in significant losses for airlines and negatively affect socioeconomic benefits. Therefore, conducting comprehensive studies on flash heavy rain is crucial for ensuring aviation safety and enhancing flight punctuality. A thorough analysis of sufficiently detailed observational data is beneficial for clarifying the dynamic mechanisms of convective organisation and enhancement. On July 15, 2022, Xiamen Airport experienced a rare flash heavy rain event triggered by a weak background gust front. During this period, the precipitation intensity peaked at 2.5 mm per minute, and runway visibility rapidly decreased to 600 m, which is relatively uncommon at Xiamen Airport. To analyse this flash heavy rain event, this study utilises minute rainfall data from both ends of the runway, conventional observational data, densified automatic weather station data, ERA5 reanalysis, and S-band dual-polarisation and X-band dual-polarisation phased array radar data of Xiamen. The results of the study indicate that this event occurred under weak weather-scale forcing, where the gust front triggered uplift by intersecting and merging with the surface convergence line during propagation. In an environment characterised by negative large values of pseudo-equivalent potential temperature (θse500-850 hPa) and a warm and humid lower atmosphere, new convection was stimulated, resulting in the rare flash heavy rain at Xiamen Airport. During heavy rain, strong water vapour convergence appeared in the boundary layer at 1000 hPa. Minute rainfall on the runway showed an inverse correlation with visibility, but this correlation weakened when the minute rainfall exceeded 1.6 mm, and the visibility minimum lagged behind the rainfall peak by 7 minutes. Observational analysis reveals that the cyclonic shear of radial velocity was consistent with the trend of minute rainfall change. The peak minute rainfall at both ends of the runway corresponded to the peak cyclonic shear at a certain height layer, indicating a good correspondence between the two. When there was cyclonic shear in the radial velocity at heights of 2-5 km, rainfall significantly intensified. When the shear intensity at two height layers exceeded 2×10-3s-1, minute rainfall could reach approximately 2 mm (equivalent to an hourly rainfall of 120 mm), which emerged as a characteristic feature of this flash heavy rain event.
    2024,52(3):309-317, DOI: 10.19517/j.1671-6345.20230123
    [Abstract] (359) [HTML] (0) [PDF 8.58 M] (19397)
    Abstract:
    Aiming at the problems of data quality degradation caused by multi-channel scanning-type loads on geostationary orbit remote sensing satellites in the process of imaging, transmission and storage, i.e., the influence of texture distortion and edge blurring in the meteorological remote sensing feature recognition images on the analysis of meteorological remote sensing images, this study proposes an improved BM3D noise reduction algorithm. The algorithm combines Morlet wavelet decomposition theory (with good symmetry and its decay characteristics follow the exponential law, it is able to match the mutation signals in the meteorological remote sensing images, thus realising signal denoising) and BM3D denoising principle (a non-local filtering algorithm that includes two parts: block matching and 3D collaborative filtering. Block matching involves grouping image blocks similar to a given reference block and composing them into a 3D array). Firstly, the image decomposes using wavelet transform to get four components. Secondly, the meteorological remote sensing image decomposes into three levels with a total of ten components. Finally, each component denoises using a separate BM3D filter, and the output image of the 10 components reconstructs. The output reconstructed image views as an estimate of the desired image, capable of suppressing meteorological remote sensing image noise and preserving edge detail. Compared with the traditional BM3D denoising algorithm, the improved BM3D algorithm is able to reduce the computation by about one-fifth. The eight meteorological remote sensing images process by equalising the grayscale and adding additive Gaussian white noise with mean 0 and standard deviation σ and random impulse noise. The median filter (suitable for removing isolated noise such as pepper noise), mean filter (suitable for removing noise from images), NL-Bayes (suitable for smoothing images and preserving image details), BM3D algorithm and the improved BM3D algorithm also compare to process the images respectively, and based on the results of peak signal-to-noise ratio (according to the definition of peak signal-to-noise ratio, it considers as the main metric to evaluate the quality of an image and utilises to measure the degree of realism of an image, with higher values indicating better denoising effects) of the meteorological remote sensing images, it finds that the average PSNR gain of the algorithms proposed in this study is in the range of 0.39 dB to 4.45 dB. The above experimental results of meteorological remote sensing images indicate that the improved BM3D algorithm works better, especially in the mixed noise denoising of Gaussian white noise and impulse noise.
    2024,52(3):424-433, DOI: 10.19517/j.1671-6345.20230152
    [Abstract] (308) [HTML] (0) [PDF 9.05 M] (19320)
    Abstract:
    In order to further strengthen the application of satellite-to-ground lightning, the spatial-temporal distribution characteristics and spatial-temporal matching features are comparatively analysed in Zhejiang Province based on lightning data from FengYun (FY)-4A Lightning Mapping Imager (LMI) and Advanced Direction and Time-of-arrival Detecting (ADTD)-2C three-dimensional lightning location system from June to August in 2020. In addition, by combining reflectivity of Doppler radar mosaics and cloud top brightness temperature from FY-4A Advanced Geosynchronous Radiation Imager (AGRI), the spatial and temporal evolution patterns of lightning data from two observation systems are analysed during a thunderstorm process in Zhejiang Province on 15 July 2020. The results show that from June to August in 2020, the number of LMIG detected by LMI was 8483, while the number of lightning detected by the ADTD-2C three-dimensional lightning location system was 376932. The ratio of the two sets of data was approximately 1∶44.43. The monthly and spatial distributions of lightning detected by these two systems were generally consistent, while diurnal variation of which were different. Specifically, diurnal variation of LMIG presented two peaks, and diurnal variation of three-dimensional lightning showed only one peak. Besides, when the time matching window was larger than 1.8 seconds, and the latitude and longitude matching window was larger than 0.5°, the matching rate gradually tended to be stable. Furthermore, the height of three-dimensional lightning matched with LMIG was mainly concentrated below 16 km, and the lightning intensity of which was mainly concentrated below 50 kA. During the thunderstorm weather in Zhejiang Province in the afternoon on 15 July 2020, the ratio of LMIG to three-dimensional lightning was approximately 1∶25.44. The time of the first LMIG and its peak time were both later than the time of the first three-dimensional lightning and its peak time. What’s more, the lightning data observed by the two systems corresponded well with the development process of the thunderstorm. When the thunderstorm was at the developing stage, the number of lightning data detected by the two systems was both gradually increasing, and when the thunderstorm was at the mature stage, the number of lightning data detected by the two systems was both maintaining a relatively high value, and when the thunderstorms were at the dissipation stage, the number of lightning data detected by the two systems was both decreasing rapidly. When it came to the spatial distribution of the lightning, both of the two datasets corresponded well with the spatial distribution of low cloud top brightness temperature.
    2024,52(3):367-379, DOI: 10.19517/j.1671-6345.20230172
    [Abstract] (198) [HTML] (0) [PDF 13.77 M] (19311)
    Abstract:
    Based on the ensemble forecast data derived from European Centre for Medium-range Weather Forecasts (ECMWF) ensemble forecast system and observation data derived from automatic observation stations in Zhejiang region, the Bayesian Model Averaging (BMA) method is used to calibrate the probabilistic forecasts of precipitation during the super long Meiyu season in 2020. In this paper, we verify the raw ensemble probabilistic forecast and BMA calibrated probabilistic forecast from 1 June to 15 July, 2020, by Mean Absolute Error (MAE), Continuous Ranked Probability Score (CRPS), Brier Score (BS), Talagrand, Probability Integral Transform (PIT) histogram, and attribute diagram. The verification results before and after calibration are compared. The analysis results are listed as follows. (1) In 8 different training periods (10 days to 80 days), 50 days correspond to smaller MAE and CRPS score values. So we set 50 days as the optimal BMA training period for ECMWF ensemble forecast calibration in the Meiyu season in Zhejiang Province. After BMA calibration in the optimal training period, the spread of ensemble forecast increases and the forecast error decreases. Analysing from the quantitative verification indicators, BMA can effectively calibrate the overall precipitation in the test stage, but it cannot calibrate the daily precipitation in the test stage. (2) For forecasting of different threshold precipitation, BMA has different calibration performance. For the thresholds of 0.1 mm, 10.0 mm, and 25.0 mm, BMA has a significant calibration effect. After BMA calibration, the CRPS of precipitation probabilistic forecast for these three thresholds (0.1 mm, 10.0 mm, and 25.0 mm) decreases by 25.92%, 19.29%, and 4.76%, respectively. However, the calibration effect of BMA weakens with the increase of precipitation threshold. For the events with total precipitation exceeding 50.0 mm, the BMA calibration effect is not as significant as that of the smaller threshold. In addition, BMA can effectively improve the forecast skills of 0.1 mm, 10.0 mm and 25.0 mm threshold precipitation and make the forecast probability more closely match the observation. (3) In the case of heavy rain, the high probability range of the raw ensemble probabilistic forecast is always wider than that of the observation. BMA has the ability to slightly calibrate the raw ensemble forecast probability. After BMA calibration, the high probability range of precipitation forecast at each threshold effectively reduces the deviation. The empty message information and the probability of empty message events also reduce after calibration. So BMA can make the calibrated high probability range of precipitation forecast more consistent with the observed range. But unfortunately, BMA cannot adjust the spatial distribution of precipitation forecast probability.
    2024,52(3):330-339, DOI: 10.19517/j.1671-6345.20230166
    [Abstract] (459) [HTML] (0) [PDF 1.48 M] (19293)
    Abstract:
    In order to apply the Hail Detection Algorithm (HDA) related products more extensively and correctly, for the 22 hail cases monitored in Pu’er area from 2015 to 2020, the new Radar Operational Software Engineering (ROSE2.0) is used to replay radar-based data and analyse the relevant products. The recognition effect of the HDA algorithm in the Pu’er area is evaluated with the probability of detection (POD), false alarm rate (FAR), and critical success index (CSI), and a localised parameter configuration scheme is provided after that, which is useful to improve the local hail warning ability. The results show that although the POD of the HDA algorithm in Pu’er area is close to 100%, there are also many ordinary storm cells that are identified as hail cells mistakenly. The number of false alarms is very huge, and the low CSI cannot meet the requirement of the weather forecasting operation. The warning effect of using Probability of Severe Hail (POSH) is better than that of Probability of Hail (POH) for any size of hail, and the larger the size of hail, the lower the probability of false alarm of POSH. Further analysis of the adaptation parameters of the POSH algorithm by a simulation test method shows that the height of the 0 ℃ and -20 ℃ layers has a significant impact on the recognition ability of POSH, the original default value is significantly lower in Pu’er area, correctly inputting the height of 0 ℃ and -20 ℃ layers on the day of hail can effectively reduce the FAR and improve the CSI of POSH; at the same time, it can control the situation that the maximum hail diameter predicted by the algorithm is generally too large, and the maximum expected hail size (MEHS) is closer to the observation value; the deviation percentage of small and medium-sized hail diameter decreases by 76.07%, with a significantly higher improvement effect than large hail, but the diameter prediction error of MEHS for large hail is smaller. In addition, increasing the reflectivity factor and POSH threshold can effectively control FAR, but it also leads to a rapid increase in the number of missed alarms. When the threshold is too large, the POD significantly decreases. In order to achieve a higher POD and CSI, selecting Z=50 dBz or POSH=70% as the threshold can improve the recognition effect of the HDA algorithm. Setting the optimal threshold of multiple parameters at the same time can effectively improve the recognition ability of the HDA algorithm in Pu’er.
    2024,52(3):340-346, DOI: 10.19517/j.1671-6345.20230182
    [Abstract] (223) [HTML] (0) [PDF 2.24 M] (19241)
    Abstract:
    In order to achieve the goal of independent and controllable key core technologies for Meteo by 2025, the Meteo Big Data Cloud Platform (referred to as Tianqing) establishes a simulation environment based on Hygon X86 CPU and Kylin OS. However, in the operation of simulation platforms, it finds that the docker scheduling performance of data processing and assembly line subsystems based on Kubernetes is poor, which cannot meet the timeliness requirements of user integration algorithms. In response to this issue, this article adopts a comparative analysis method, selecting servers based on three types of CPU and three types of operating systems from the simulation environment and business environment for Tianqing as the research objects. A series of combined comparative test cases are designed. It finds that the kernel is the key factor affecting docker scheduling performance. Further analysis is conducted on the impact of operating system kernel settings on real-time and throughput, as well as the suitable business scenarios. Finally, a method for adjusting the Kylin OS kernel is provided. By adjusting the kernel settings, the docker scheduling performance significantly improves, meeting the timeliness requirements of the data processing system and laying the foundation for achieving self-supporting of the key core technology of Tianqing.
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    2004,32(4):251, DOI:
    [Abstract] (6128) [HTML] (0) [PDF 423.81 K] (5796)
    Abstract:
    CINRAD/SA, China Next Generation Weather Radar,was produced by the Beijing METSATAR Radar Co., Ltd, based on the NEXRAD WSR-88D technology.Its software system was modified to provide the new RHI/PPI scan mode because NEXRAD WSR-88D provides only the volume scan mode. The design and realization of the RHI/PPI scan mode on the CINRAD/SA are described.
    2008,36(6):760-763, DOI:
    [Abstract] (5711) [HTML] (0) [PDF 464.40 K] (5617)
    Abstract:
    An analysis is made of the annual, seasonal, and monthly variation characteristics of sunshine duration in recent 50 years and its relationship with total cloudiness, trying to detect the variation of sunshine duration in Chengdu by the abrupt climate change theory. The results indicate that in recent 50 years, the sunshine duration decreased with a tendency of 69.41 hours per ten years; the interannual variation amplitude was obviously greater; and the difference between the sunshine durations in 1963 and in 1989 is up to 662.8 hours. There is obvious seasonal difference in sunshine duration, with bigger decreasing amplitude in summer and winter than those in spring and autumn and a tendency of -29.77 and -20.17, -9.91 and -9.56 hours per ten years, respectively. The decreasing tendency is obviously greater in August and less in April. The annual variation of sunshine duration is consistent with sunshine percentage. The sudden change occurred around 1978, with the annual sunshine duration decreased rapidly.
    2008,36(4):474-479, DOI:
    [Abstract] (4495) [HTML] (0) [PDF 650.10 K] (5154)
    Abstract:
    An observational experiment was conducted on the impact of air temperature and humidity variation on soil resistivity and earthing resistance with different structures by selecting three typical soil conditions to set three vari structure lightning protecting earthing bodies in Ningxia for one year. By means of comparative and regression analysis, the impacts of different soil conditions on soil resistivity at different temperatures and humidity in different seasons, and the variation characteristics and regularities of the lightning protecting earthing bodies with different structures are studied, and accordingly the optimal requirements for the layout and structure of lightning protecting earthing bodies are presented.
    2005,33(4):340-344, DOI:
    [Abstract] (4475) [HTML] (0) [PDF 146.22 K] (7299)
    Abstract:
    In order to develop and utilize reasonably climate resources and offer a scientific basis for the sub-area management of livestock production over grasslands, an analysis was made of the Inner Mongolia grassland climate characteristics and effects of climate on the growth of pasture grass, the distribution of domestic animal breeds and the soil environment. It is found that some isolines of climatic moisture are almost superposed with the boundaries of soil, which indicates that the formation of soil zones is closely related to climatic conditions, and climate and soil environment are main influence factors for pasture types and the ecosystem. Based on the climatic moisture, in combination with the distribution characteristics of soil over Inner Mongolia, a regionalization was carried out of grassland ecological types, which is not only rational, but also stable. It is pointed out that the climatic warming and the resulting changes in recent years improved, to some extent, the productivity of the grasslands, but not changed the ecotype in Inner Mongolia.
    2010,38(1):1-8, DOI:
    [Abstract] (3936) [HTML] (0) [PDF 988.69 K] (8238)
    Abstract:
    An introduction of the main reanalysis data of NCEP, ECMWF, JMA and the preliminary comparison among them are given from the following aspects: (1) assimilation systems, including the assimilation module and method; (2) the data used in the reanalysis; and (3) the methods of quality control and bias correction. The main assimilation methods of all reanalysis datasets include the 3D variational method, 4D variational method, and optimum interpolation. The dominating differences of these reanalysis datasets are data types and the resolution of modules. In addition, the advantages and deficiencies of these reanalysis datasets are given by empirical analysis. It is helpful for selecting the correct reanalysis dataset. The advances in reanalysis in China ars introduced simply and some problems on the improvement of the reanalysis in China are discussed.

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