Volume 48,Issue 5,2020 Table of Contents
2020, 48(5):615-621.
Abstract:
The Meteorological decision service mobile platform of the National Meteorological Center （NMC） is designed and developed by the NMC researchers for the massive meteorological data and efficient demands of meteorological disaster emergency service. The paper introduces the structure of the mobile platform server and client, and the platform functions such as observation, locationbased service (LBS) gridded forecast, early warning, decision service product delivering, disastrous weather autowarning and delivering and so on. This platform adopts the realtime distributed process computation to solve the massive data processing and analysis efficiently in mobile mode, and visualize and interoperate massive meteorological data based on HTML5 and mobile GIS technologies. This platform has already been stably applied in the national and provincial meteorological decision service operations, such as typhoon, storm and other disaster emergency service. The efficient and convenient functions of this platform illustrate that the platform has strong practicability.
The Meteorological decision service mobile platform of the National Meteorological Center （NMC） is designed and developed by the NMC researchers for the massive meteorological data and efficient demands of meteorological disaster emergency service. The paper introduces the structure of the mobile platform server and client, and the platform functions such as observation, locationbased service (LBS) gridded forecast, early warning, decision service product delivering, disastrous weather autowarning and delivering and so on. This platform adopts the realtime distributed process computation to solve the massive data processing and analysis efficiently in mobile mode, and visualize and interoperate massive meteorological data based on HTML5 and mobile GIS technologies. This platform has already been stably applied in the national and provincial meteorological decision service operations, such as typhoon, storm and other disaster emergency service. The efficient and convenient functions of this platform illustrate that the platform has strong practicability.
2020, 48(5):622-629.
Abstract:
The uncertainty of the satellite precipitation products limits their applicability in coastal areas. This paper evaluates the applicability of a new precipitation product IMERG from Global Precipitation Measurements (GPM) in Sanya based on the meteorological stations data. The measured precipitation data of meteorological stations in 2016 are used to evaluate and compare the accuracy of IMERG data. Correlation coefficient, Standard Deviation and Percent Bias are used to assess the applicability of IMERG data. The results show: There was a significant correlation between IMERG and the observed data. The IMERG precipitation data and the measured precipitation from meteorological stations have an identical spatialtemporal variation regularity, but in the mountain areas and islands, the estimated precipitation of IMERG is not as good as that in plain areas. At the same time, the analysis of daily and halfhour IMERG data shows that there are also deviations of the precipitation estimated by daily IMERG data for different grades, and the estimated precipitation of halfhour IMERG data is higher in the island stations. Generally speaking, IMERG precipitation data are reasonable in estimating temporal variation and spatial distribution patterns of precipitation, but there are still some deviations in the estimation of rainfall in mountainous and island areas. Therefore, IMERG data should be used reasonably in combination with topographic information in the future.
The uncertainty of the satellite precipitation products limits their applicability in coastal areas. This paper evaluates the applicability of a new precipitation product IMERG from Global Precipitation Measurements (GPM) in Sanya based on the meteorological stations data. The measured precipitation data of meteorological stations in 2016 are used to evaluate and compare the accuracy of IMERG data. Correlation coefficient, Standard Deviation and Percent Bias are used to assess the applicability of IMERG data. The results show: There was a significant correlation between IMERG and the observed data. The IMERG precipitation data and the measured precipitation from meteorological stations have an identical spatialtemporal variation regularity, but in the mountain areas and islands, the estimated precipitation of IMERG is not as good as that in plain areas. At the same time, the analysis of daily and halfhour IMERG data shows that there are also deviations of the precipitation estimated by daily IMERG data for different grades, and the estimated precipitation of halfhour IMERG data is higher in the island stations. Generally speaking, IMERG precipitation data are reasonable in estimating temporal variation and spatial distribution patterns of precipitation, but there are still some deviations in the estimation of rainfall in mountainous and island areas. Therefore, IMERG data should be used reasonably in combination with topographic information in the future.
2020, 48(5):630-634.
Abstract:
Acquired by the Fengyun4 meteorological satellite ranging system, the distance from the ground station on the earth to the satellite is the main factor influencing the accuracy of the satellite’s orbit determination. After introducing the working principles and procedure of the Fengyun4 ranging system, the techniques used to improve the ranging precision are analyzed from different aspects, including the measurements in the stations’ site coordinates, the delay caused by ground equipment, satellite transponder, propagation through atmosphere and the time synchronization of different stations.
Acquired by the Fengyun4 meteorological satellite ranging system, the distance from the ground station on the earth to the satellite is the main factor influencing the accuracy of the satellite’s orbit determination. After introducing the working principles and procedure of the Fengyun4 ranging system, the techniques used to improve the ranging precision are analyzed from different aspects, including the measurements in the stations’ site coordinates, the delay caused by ground equipment, satellite transponder, propagation through atmosphere and the time synchronization of different stations.
2020, 48(5):635-639.
Abstract:
The article mainly analyzes the measurement 〖JP2〗errors based on the structural principle of the SL31〖JP〗 double tipping bucket rainfall sensor. According to the different water capacities of the sensor tipping bucket, the precipitation errors are compared by a precipitation simulation experiment. The purpose is to obtain the proper proportional relationship between the upper bucket and the metering bucket when measuring 10 mm precipitation under the heavy and light rainfall intensities (1 mm/min and 4 mm/min). Therefore, the measurement errors are minimized and the measurement error consistency is the best under the two rain intensities. The results show that for the 10 mm precipitation measurement, the most appropriate ratio of the number of times the upper bucket turned to that of the measuring bucket turned is 9∶10. The determination of the proportional relationship provides a technical reference and basis for the outoftolerance adjustment of the double tipping bucket rainfall sensor, and provides guarantees for the accuracy and reliability of the rainfall observation data.
The article mainly analyzes the measurement 〖JP2〗errors based on the structural principle of the SL31〖JP〗 double tipping bucket rainfall sensor. According to the different water capacities of the sensor tipping bucket, the precipitation errors are compared by a precipitation simulation experiment. The purpose is to obtain the proper proportional relationship between the upper bucket and the metering bucket when measuring 10 mm precipitation under the heavy and light rainfall intensities (1 mm/min and 4 mm/min). Therefore, the measurement errors are minimized and the measurement error consistency is the best under the two rain intensities. The results show that for the 10 mm precipitation measurement, the most appropriate ratio of the number of times the upper bucket turned to that of the measuring bucket turned is 9∶10. The determination of the proportional relationship provides a technical reference and basis for the outoftolerance adjustment of the double tipping bucket rainfall sensor, and provides guarantees for the accuracy and reliability of the rainfall observation data.
2020, 48(5):640-647.
Abstract:
In order to improve the service capability of monitoring and forecasting agricultural droughts and reduce the impact of agricultural droughts on social life and production, this paper sorts out and perfects the collection, storage, processing, production and release of drought information, and builds an operational agricultural drought monitoring and forecasting system for Liaoning Province, which realizes the integration, refinement, quantitative monitoring and forecasting of agricultural droughts, as well as the standardization, automatic production and distribution of drought products. Depending on meteorological drought monitoring technology, agricultural drought monitoring technology and remote sensing drought monitoring technology, the functions of observation data collecting and storing, drought information displaying and analyzing, drought product making and releasing are realized, and the integrated drought service system of provincial, city and county levels is finally formed, so as to improve the capability of disaster prevention and mitigation in response to drought disasters. The operational application of the system improves the quantitative, automatic and intelligent level of agricultural drought monitoring and prediction, and the operational capability of ground and satellite remote sensing drought monitoring and prediction. The integrated service mode of provincial, city and county levels constructed by the system facilitates the provincial operation center to produce drought products in a unified way, which allows the specialists of the provincial, municipal and county levels to simultaneously carry out refined drought guidance services.
In order to improve the service capability of monitoring and forecasting agricultural droughts and reduce the impact of agricultural droughts on social life and production, this paper sorts out and perfects the collection, storage, processing, production and release of drought information, and builds an operational agricultural drought monitoring and forecasting system for Liaoning Province, which realizes the integration, refinement, quantitative monitoring and forecasting of agricultural droughts, as well as the standardization, automatic production and distribution of drought products. Depending on meteorological drought monitoring technology, agricultural drought monitoring technology and remote sensing drought monitoring technology, the functions of observation data collecting and storing, drought information displaying and analyzing, drought product making and releasing are realized, and the integrated drought service system of provincial, city and county levels is finally formed, so as to improve the capability of disaster prevention and mitigation in response to drought disasters. The operational application of the system improves the quantitative, automatic and intelligent level of agricultural drought monitoring and prediction, and the operational capability of ground and satellite remote sensing drought monitoring and prediction. The integrated service mode of provincial, city and county levels constructed by the system facilitates the provincial operation center to produce drought products in a unified way, which allows the specialists of the provincial, municipal and county levels to simultaneously carry out refined drought guidance services.
2020, 48(5):648-654.
Abstract:
The allforone tourism meteorological service system model based on multisource data integration technology is designed based on the needs of allforone tourism weather services. According to the model, the local weather, geography, tourism, ecology, economy, society and other multisource data from Hainan Province are combined to develop a “sitebased weather navigation map of scenic roads” on WeChat. Through actual operational application for a period of time, the system can provide more accurate comprehensive tourism information for clothing, food, housing, travel, and entertainment, as a reference for tourists, to avoid harm and enhance the capabilities of overall tourism weather service in Hainan. At the same time, some problems that need further improvement and optimization are also discussed.
The allforone tourism meteorological service system model based on multisource data integration technology is designed based on the needs of allforone tourism weather services. According to the model, the local weather, geography, tourism, ecology, economy, society and other multisource data from Hainan Province are combined to develop a “sitebased weather navigation map of scenic roads” on WeChat. Through actual operational application for a period of time, the system can provide more accurate comprehensive tourism information for clothing, food, housing, travel, and entertainment, as a reference for tourists, to avoid harm and enhance the capabilities of overall tourism weather service in Hainan. At the same time, some problems that need further improvement and optimization are also discussed.
2020, 48(5):655-663.
Abstract:
Studying the climatic characteristics of gravity wave parameters constitutes an important part of the parameterization of gravity waves in the development of a global atmospheric model. The disturbance fields obtained by using the highresolution radiosonde data are the basic data and important means to obtain the climate characteristics of gravity wave parameters. At present, the 2 to 4 order curve fitting and bandpass filtering methods are used to obtain the disturbance fields of high vertical resolution radiosonde data. However, there are few studies on the differences in the characteristics of disturbance fields resulted from different methods. In the paper, the disturbance fields of the high vertical resolution radiosonde data in Taiyuan (112.55°E, 37.78°N) from 2014 to 2017 are obtained by the 2 to 4 order curve fitting and bandpass filtering methods (0.5 to 5.0 km), subsequently, studied by correlation coefficient, LombScargle, and different interval range occupancy methods. The results show: (1) the disturbance fields from differentorder curve fitting methods show different amplitudes, different trends with height, and weak correlation; (2) the LombScargle analysis shows that the significant vertical wavelengths (passed the 90% confidence test) are contained in the average zonal wind disturbance fields, the average meridional wind disturbance fields and the average temperature disturbance fields from different methods, and there are significant differences; (3) the significant vertical wavelengths are contained in the zonal wind disturbance fields, meridional wind disturbance fields and temperature disturbance fields from different methods, and there are significant differences in their occupancy rate within different intervals.
Studying the climatic characteristics of gravity wave parameters constitutes an important part of the parameterization of gravity waves in the development of a global atmospheric model. The disturbance fields obtained by using the highresolution radiosonde data are the basic data and important means to obtain the climate characteristics of gravity wave parameters. At present, the 2 to 4 order curve fitting and bandpass filtering methods are used to obtain the disturbance fields of high vertical resolution radiosonde data. However, there are few studies on the differences in the characteristics of disturbance fields resulted from different methods. In the paper, the disturbance fields of the high vertical resolution radiosonde data in Taiyuan (112.55°E, 37.78°N) from 2014 to 2017 are obtained by the 2 to 4 order curve fitting and bandpass filtering methods (0.5 to 5.0 km), subsequently, studied by correlation coefficient, LombScargle, and different interval range occupancy methods. The results show: (1) the disturbance fields from differentorder curve fitting methods show different amplitudes, different trends with height, and weak correlation; (2) the LombScargle analysis shows that the significant vertical wavelengths (passed the 90% confidence test) are contained in the average zonal wind disturbance fields, the average meridional wind disturbance fields and the average temperature disturbance fields from different methods, and there are significant differences; (3) the significant vertical wavelengths are contained in the zonal wind disturbance fields, meridional wind disturbance fields and temperature disturbance fields from different methods, and there are significant differences in their occupancy rate within different intervals.
2020, 48(5):664-674.
Abstract:
Based on the mesoscale numerical forecast system that is operationally implemented in the Chongqing Meteorological Service, the influence of different terrain smoothing schemes in the WRF model on precipitation forecast is studied. The differences between the static terrain height fields generated without smoothing and with two smoothing schemes (sds and 121) in the WRF model are studied and compared in detail. Based on this, one month consistent experiments using different terrain smoothing schemes were carried out, and a typical heavy precipitation case was selected for further comparative analysis. The results show that there are obvious difference between the static terrain height fields generated by different terrain smoothing schemes, especially for the steep plateau regions or mountain regions while the maximum mean absolute error can be more than 462.56 m; the two terrain smoothing schemes (sds and 121) mainly smooth out the topographic features of small scale in the mode terrain, and in general, the smoothing degree of the 121 scheme is greater than that of the sds scheme. The verification results of the one month consistent experiments show that the model terrain smoothing process has a positive impact on the forecasts of heavy or above rainfall, and the prediction results using the 121 smoothing scheme are better than those using the sds smoothing scheme. The comparative analysis results of a typical precipitation case show that different terrain smoothing schemes will cause significant differences in the prediction of vertical velocity and water vapor flux divergence, and such significant differences will further affect the fall area and intensity of heavy precipitation prediction.
Based on the mesoscale numerical forecast system that is operationally implemented in the Chongqing Meteorological Service, the influence of different terrain smoothing schemes in the WRF model on precipitation forecast is studied. The differences between the static terrain height fields generated without smoothing and with two smoothing schemes (sds and 121) in the WRF model are studied and compared in detail. Based on this, one month consistent experiments using different terrain smoothing schemes were carried out, and a typical heavy precipitation case was selected for further comparative analysis. The results show that there are obvious difference between the static terrain height fields generated by different terrain smoothing schemes, especially for the steep plateau regions or mountain regions while the maximum mean absolute error can be more than 462.56 m; the two terrain smoothing schemes (sds and 121) mainly smooth out the topographic features of small scale in the mode terrain, and in general, the smoothing degree of the 121 scheme is greater than that of the sds scheme. The verification results of the one month consistent experiments show that the model terrain smoothing process has a positive impact on the forecasts of heavy or above rainfall, and the prediction results using the 121 smoothing scheme are better than those using the sds smoothing scheme. The comparative analysis results of a typical precipitation case show that different terrain smoothing schemes will cause significant differences in the prediction of vertical velocity and water vapor flux divergence, and such significant differences will further affect the fall area and intensity of heavy precipitation prediction.
2020, 48(5):675-684.
Abstract:
In this paper, coupling with the Noah land surface model and CLM lake model, the WRF model is used to simulate a gale event in the Erhai basin, Dali of Yunnan Province on 23 January 2015. An analysis is made of the characteristics of 3D dynamic and thermal structure in the onset, prevailing and retreat periods of the gale and its mechanism is analyzed. In the onset period of gale, the west wind dominated in the upper atmosphere, the local small cyclone appeared at the height of 1 km around the central Erhai basin, and the east wind dominated on the ground. The westerly flow in the upper atmosphere created fluctuation disturbance over Mt. Cangshan, and the cavity zone and secondary vertex in the leeward slope, and unstable wave region in the lowerlevel atmosphere. The unstable wave broke in the lowerlevel atmosphere, where the turbulences were quite active. The energy in the upper atmosphere was transported downwards. In the prevailing period of the gale, the upper atmosphere over the south and north parts of the Erhai basin was controlled by two westerly flows, while the upper atmosphere over the central part of the basin was a weak divergence field. This structure over the Erhai basin brought about disturbance in the upper atmosphere, which made the shallow inversion layer near the surface layer over the east part of Mt. Cangshan disappear, and temperature above this shallow inversion layer increase with height. The atmosphere was unstable and beneficial to momentum being transported downwards from the upper atmosphere. In the retreat period of the gale, the west wind in the upper atmosphere weakened, the disturbance disappeared, turbulent kinetic energy dissipated, and the wind at ground level decreased.
In this paper, coupling with the Noah land surface model and CLM lake model, the WRF model is used to simulate a gale event in the Erhai basin, Dali of Yunnan Province on 23 January 2015. An analysis is made of the characteristics of 3D dynamic and thermal structure in the onset, prevailing and retreat periods of the gale and its mechanism is analyzed. In the onset period of gale, the west wind dominated in the upper atmosphere, the local small cyclone appeared at the height of 1 km around the central Erhai basin, and the east wind dominated on the ground. The westerly flow in the upper atmosphere created fluctuation disturbance over Mt. Cangshan, and the cavity zone and secondary vertex in the leeward slope, and unstable wave region in the lowerlevel atmosphere. The unstable wave broke in the lowerlevel atmosphere, where the turbulences were quite active. The energy in the upper atmosphere was transported downwards. In the prevailing period of the gale, the upper atmosphere over the south and north parts of the Erhai basin was controlled by two westerly flows, while the upper atmosphere over the central part of the basin was a weak divergence field. This structure over the Erhai basin brought about disturbance in the upper atmosphere, which made the shallow inversion layer near the surface layer over the east part of Mt. Cangshan disappear, and temperature above this shallow inversion layer increase with height. The atmosphere was unstable and beneficial to momentum being transported downwards from the upper atmosphere. In the retreat period of the gale, the west wind in the upper atmosphere weakened, the disturbance disappeared, turbulent kinetic energy dissipated, and the wind at ground level decreased.
2020, 48(5):685-694.
Abstract:
Improving the capability of extendedrange forecast of precipitation during the Meiyu season has become an important research area for operational developments of both weather forecast and climate prediction. By taking the Meiyu season in Shanghai as an example, this paper analyzes the characteristics of intraseasonal pentad anomalies of Meiyu precipitation and its associating key lowfrequency signals on the extendedrange scale through investigating multivariable intraseasonal components extracted by nontraditional filtering. An extendedrange forecast model of pentad precipitation anomalies during the Meiyu season is further established by integrating the multivariable lowfrequency signals, and the performances of the forecast model are evaluated by the hindcasts and forecast experiments. Results show that: (1) The intraseasonal component of pentad precipitation anomaly during the Meiyu season has significant features of 40 to 60 day lowfrequency oscillation, which also has an significant positive correlation and high sign consistency rate with the observed precipitation anomaly. (2) The intraseasonal pentad anomaly of Meiyu precipitation is related to the low frequency signals from both tropics and the middlehigh latitudes, such as the eastward propagation of tropical MJO from the Arabian sea, the northwestward propagation of the western Pacific subtropical high, the intraseasonal phase conversion of PNA (PacificNorth American) teleconnection and the persistent anomaly influences of cold air activities in Northeast Asia. (3) The extendedrange forecast model of the pentad precipitation anomalies by integrating the above multivariable lowfrequency signals is statistically skillful to forecast the intraseasonal component of pentad precipitation anomalies with a leading time of 10 to 35 days. It also shows outstanding capability in predicting the trend of the observed pentad precipitation anomaly.
Improving the capability of extendedrange forecast of precipitation during the Meiyu season has become an important research area for operational developments of both weather forecast and climate prediction. By taking the Meiyu season in Shanghai as an example, this paper analyzes the characteristics of intraseasonal pentad anomalies of Meiyu precipitation and its associating key lowfrequency signals on the extendedrange scale through investigating multivariable intraseasonal components extracted by nontraditional filtering. An extendedrange forecast model of pentad precipitation anomalies during the Meiyu season is further established by integrating the multivariable lowfrequency signals, and the performances of the forecast model are evaluated by the hindcasts and forecast experiments. Results show that: (1) The intraseasonal component of pentad precipitation anomaly during the Meiyu season has significant features of 40 to 60 day lowfrequency oscillation, which also has an significant positive correlation and high sign consistency rate with the observed precipitation anomaly. (2) The intraseasonal pentad anomaly of Meiyu precipitation is related to the low frequency signals from both tropics and the middlehigh latitudes, such as the eastward propagation of tropical MJO from the Arabian sea, the northwestward propagation of the western Pacific subtropical high, the intraseasonal phase conversion of PNA (PacificNorth American) teleconnection and the persistent anomaly influences of cold air activities in Northeast Asia. (3) The extendedrange forecast model of the pentad precipitation anomalies by integrating the above multivariable lowfrequency signals is statistically skillful to forecast the intraseasonal component of pentad precipitation anomalies with a leading time of 10 to 35 days. It also shows outstanding capability in predicting the trend of the observed pentad precipitation anomaly.
2020, 48(5):695-703.
Abstract:
Based on the typhoon (TC) data in 1949-2016 and daily precipitation data of the surface climate data in China, (annual: June to October; monthly: July to September) mean precipitation characteristics in the western China under the background of TC activity and their landing are studied by using the statistical analysis and long sample data. The results are as follows: (1) In 67 years, the annual average number of the TCs landing on the mainland of China is 9.09. The active phase of typhoons is June to October. The TC landing appeared first in April and the latest in December, and the highest frequency of the landing typhoon is in August. (2) Typhoon activity has a significant impact on the precipitation in Ningxia, Shaanxi, the Sichuan Basin, the central and eastern Gansu and Qinghai. The numbers of typhoon activities are positively correlated with the precipitation in the corresponding areas. The precipitation in Xinjiang and the Tibet is very little affected by typhoons, and in Guizhou and Chongqing, the correlation is reverse. TC activities have little effect on precipitation in Yunnan. (3) TC activities are positively correlated with precipitation in some parts of the western China, which is the most significant for the annual average precipitation, followed by the precipitation from June to October. The characteristics of longdistance TC and precipitation in the western China are focused in this study, which will help systematically and comprehensively understand the characteristics of TC activities, the relationship between landing TC and precipitation in the western China and the mechanisms of precipitation in the western China.
Based on the typhoon (TC) data in 1949-2016 and daily precipitation data of the surface climate data in China, (annual: June to October; monthly: July to September) mean precipitation characteristics in the western China under the background of TC activity and their landing are studied by using the statistical analysis and long sample data. The results are as follows: (1) In 67 years, the annual average number of the TCs landing on the mainland of China is 9.09. The active phase of typhoons is June to October. The TC landing appeared first in April and the latest in December, and the highest frequency of the landing typhoon is in August. (2) Typhoon activity has a significant impact on the precipitation in Ningxia, Shaanxi, the Sichuan Basin, the central and eastern Gansu and Qinghai. The numbers of typhoon activities are positively correlated with the precipitation in the corresponding areas. The precipitation in Xinjiang and the Tibet is very little affected by typhoons, and in Guizhou and Chongqing, the correlation is reverse. TC activities have little effect on precipitation in Yunnan. (3) TC activities are positively correlated with precipitation in some parts of the western China, which is the most significant for the annual average precipitation, followed by the precipitation from June to October. The characteristics of longdistance TC and precipitation in the western China are focused in this study, which will help systematically and comprehensively understand the characteristics of TC activities, the relationship between landing TC and precipitation in the western China and the mechanisms of precipitation in the western China.
12 Characteristics of Persistent Heavy Rainfall and Water Vapor Transport in Western Sichuan Plateau
2020, 48(5):704-716.
Abstract:
Based on the routine observational data, NCEP FNL data and the HYSPLIT model, the spatiotemporal distribution, circulation situation, water vapor source and transport path of the persistent heavy rainfall events in the western Sichuan Plateau from 2008 to 2017 are analyzed. The main results are as follows: The total frequency of persistent heavy rainfall events in all observation stations of the western Sichuan Plateau is 337, and the frequency of regional heavy rainfall episodes is 21, in which the transition areas between plateau and basin including Luding, Kangding and Wenchuan have the highest frequency of persistent heavy rainfall. The longest duration of heavy rainfall events is about 3 to 4 days. In this study, the influencing circulation situations contains two troughs and one ridge, one trough and one ridge, and westerly trough. The cyclone over the Bay of Bengal is found to be a crucial weather system, which appears in 16 of the 21 regional persistent heavy rainfall cases. Moreover, all the regional cases in June and July are affected by the Bay of Bengal cyclone. The air masses on the western Sichuan Plateau are mainly accessed through four paths. The southwest and southeast routes originating from the tropical Indian Ocean are 43% and 11%, respectively, and the northwestern routes originating from the North Atlantic, the Mediterranean and the northcentral Iran account for 29%. The northeast path from the Caspian Sea to the Aral Sea accounts for 17%. The initial altitude of air particles of the northerly path is higher than that of the southerly path, and the corresponding temperature and water vapor content are lower. After analyzing the water vapor flux and water vapor flux divergence, the water vapor transport in regional persistent heavy rainfall in the western Sichuan Plateau is classified as three types, namely the S type, the westerly airflow type and the southerly airflow type.
Based on the routine observational data, NCEP FNL data and the HYSPLIT model, the spatiotemporal distribution, circulation situation, water vapor source and transport path of the persistent heavy rainfall events in the western Sichuan Plateau from 2008 to 2017 are analyzed. The main results are as follows: The total frequency of persistent heavy rainfall events in all observation stations of the western Sichuan Plateau is 337, and the frequency of regional heavy rainfall episodes is 21, in which the transition areas between plateau and basin including Luding, Kangding and Wenchuan have the highest frequency of persistent heavy rainfall. The longest duration of heavy rainfall events is about 3 to 4 days. In this study, the influencing circulation situations contains two troughs and one ridge, one trough and one ridge, and westerly trough. The cyclone over the Bay of Bengal is found to be a crucial weather system, which appears in 16 of the 21 regional persistent heavy rainfall cases. Moreover, all the regional cases in June and July are affected by the Bay of Bengal cyclone. The air masses on the western Sichuan Plateau are mainly accessed through four paths. The southwest and southeast routes originating from the tropical Indian Ocean are 43% and 11%, respectively, and the northwestern routes originating from the North Atlantic, the Mediterranean and the northcentral Iran account for 29%. The northeast path from the Caspian Sea to the Aral Sea accounts for 17%. The initial altitude of air particles of the northerly path is higher than that of the southerly path, and the corresponding temperature and water vapor content are lower. After analyzing the water vapor flux and water vapor flux divergence, the water vapor transport in regional persistent heavy rainfall in the western Sichuan Plateau is classified as three types, namely the S type, the westerly airflow type and the southerly airflow type.
2020, 48(5):717-722.
Abstract:
Based on the data of buoy, island and inland stations of the Beibu Gulf from 2016 to 2017, the seasonal variation, occurrence and disappearance characteristics, and duration of fogs and the difference between sea and land heavy fogs are statistically analyzed. The result shows that the number of sea fog days occurred in 2016 is 37 and 19 in 2017. The largest number of sea fog days occurred in March; the second is in April; and there was no sea fog occurred in December and from June to October every year. The peak time of sea fog appearing was 03:00 to 05:00, and the peak time of dissipation was 08:00 to 10:00. The duration of sea fog maintenance was within 3 hours. The generation time of sea fogs was different in different areas and underlying surfaces over the Beibu Gulf. The generation time of sea fogs (buoy stations) was about 3 hours earlier than those of island fogs (Weizhou Station) and coastal fogs (Beihai Station), and the dissipation time was about 3 hours later. The sea fogs over the Beibu Gulf mostly took place under the condition when wind speed was less than 5 m/s (l to 3 m/s is most suitable) and wind direction was NNE to SE; ninetyfive percent of sea fogs occurred when the sea water temperature was lower than 25.0 ℃.
Based on the data of buoy, island and inland stations of the Beibu Gulf from 2016 to 2017, the seasonal variation, occurrence and disappearance characteristics, and duration of fogs and the difference between sea and land heavy fogs are statistically analyzed. The result shows that the number of sea fog days occurred in 2016 is 37 and 19 in 2017. The largest number of sea fog days occurred in March; the second is in April; and there was no sea fog occurred in December and from June to October every year. The peak time of sea fog appearing was 03:00 to 05:00, and the peak time of dissipation was 08:00 to 10:00. The duration of sea fog maintenance was within 3 hours. The generation time of sea fogs was different in different areas and underlying surfaces over the Beibu Gulf. The generation time of sea fogs (buoy stations) was about 3 hours earlier than those of island fogs (Weizhou Station) and coastal fogs (Beihai Station), and the dissipation time was about 3 hours later. The sea fogs over the Beibu Gulf mostly took place under the condition when wind speed was less than 5 m/s (l to 3 m/s is most suitable) and wind direction was NNE to SE; ninetyfive percent of sea fogs occurred when the sea water temperature was lower than 25.0 ℃.
14 Spatiotemporal Characteristics and Variation Trends of Annual Maximum Rainfall Intensity in Guizhou
2020, 48(5):723-730.
Abstract:
Based on the existing data of selfrecorded and automatic precipitation in Guizhou, the temporal and spatial distribution characteristics of the annual maximum rainfall intensity, the maximum rainfall intensity during 1954-2017 in national meteorological stations in Guizhou, and the variation trends of rain intensity from 1968 to 2017 are statistically analyzed. The results show that the annual rain intensity in Guizhou was between 13.6 mm to 117.4 mm per hour, and the maximum of the years in Guizhou was between 53.0 mm to 117.4 mm per hour. The hourly maximum rainfall intensity in the southwest, midwest, northeast, and southeast areas were all over 100 mm per hour. The southwest had the strongest rainfall intensity. The heavy rainfall in Guizhou occurred from March to November, mainly between May and August, while the heaviest rainfall happened in June. The heavy rainfall in Guizhou was characterized by obvious night occurrence, usually around 02:00 at midnight, more in the first half of the night than in the second half. The occurrence frequency at noontime was the least. The increase/decrease trend of rain intensity in Guizhou was not obvious, with the slight increases in southeast, south and west, and the slight decreases in northeast and northwest.
Based on the existing data of selfrecorded and automatic precipitation in Guizhou, the temporal and spatial distribution characteristics of the annual maximum rainfall intensity, the maximum rainfall intensity during 1954-2017 in national meteorological stations in Guizhou, and the variation trends of rain intensity from 1968 to 2017 are statistically analyzed. The results show that the annual rain intensity in Guizhou was between 13.6 mm to 117.4 mm per hour, and the maximum of the years in Guizhou was between 53.0 mm to 117.4 mm per hour. The hourly maximum rainfall intensity in the southwest, midwest, northeast, and southeast areas were all over 100 mm per hour. The southwest had the strongest rainfall intensity. The heavy rainfall in Guizhou occurred from March to November, mainly between May and August, while the heaviest rainfall happened in June. The heavy rainfall in Guizhou was characterized by obvious night occurrence, usually around 02:00 at midnight, more in the first half of the night than in the second half. The occurrence frequency at noontime was the least. The increase/decrease trend of rain intensity in Guizhou was not obvious, with the slight increases in southeast, south and west, and the slight decreases in northeast and northwest.
2020, 48(5):731-740.
Abstract:
Using the ground meteorological observation data, ERA5 reanalysis data, FY2E satellite and Doppler radar data, a diagnosis and analysis of a severe convective rainstorm occurred in Chaohu on 17 July 2011 is made. The weather analysis shows that the 500hPa deep trough, the 850hPa shear line, and the ground lowpressure were the synoptic scale impact systems of the heavy rain process. The precipitation process occurred in the deep wet and warm clouds, low LCL (Lifting Condensation Level), medium convection instability and weak vertical wind shear. The FY2E satellite cloud image analysis shows that the heavy precipitation process was mainly caused by the merger of multiple mesoscale convective systems in Lake Chaohu, and the shortterm heavy precipitation area mainly fell near the TBB isoline dense area of the mesoscale convective system. The stronger the TBB center intensity, the larger the TBB contour gradient, the stronger the corresponding 1hour precipitation would be. Doppler radar analysis reveals that shortterm heavy precipitation occurred during the merge of two convection echoes. The convective storm moved slowly, and the strong echoes greater than 45 dBz were below 6 km, showing lowlevel strong cyclonic convergence and highlevel divergence. The ground mesoscale convergence line was the trigger of the storm. The diagnostic results of wet potential vorticity show that convective instability below 600 hPa and symmetrical instability above 600 hPa are beneficial to the occurrence and development of heavy rain and mesoscale systems.
Using the ground meteorological observation data, ERA5 reanalysis data, FY2E satellite and Doppler radar data, a diagnosis and analysis of a severe convective rainstorm occurred in Chaohu on 17 July 2011 is made. The weather analysis shows that the 500hPa deep trough, the 850hPa shear line, and the ground lowpressure were the synoptic scale impact systems of the heavy rain process. The precipitation process occurred in the deep wet and warm clouds, low LCL (Lifting Condensation Level), medium convection instability and weak vertical wind shear. The FY2E satellite cloud image analysis shows that the heavy precipitation process was mainly caused by the merger of multiple mesoscale convective systems in Lake Chaohu, and the shortterm heavy precipitation area mainly fell near the TBB isoline dense area of the mesoscale convective system. The stronger the TBB center intensity, the larger the TBB contour gradient, the stronger the corresponding 1hour precipitation would be. Doppler radar analysis reveals that shortterm heavy precipitation occurred during the merge of two convection echoes. The convective storm moved slowly, and the strong echoes greater than 45 dBz were below 6 km, showing lowlevel strong cyclonic convergence and highlevel divergence. The ground mesoscale convergence line was the trigger of the storm. The diagnostic results of wet potential vorticity show that convective instability below 600 hPa and symmetrical instability above 600 hPa are beneficial to the occurrence and development of heavy rain and mesoscale systems.
2020, 48(5):741-751.
Abstract:
A new technique for forecasting meteorological conditions of air pollution is developed by the analysis based on Air Quality Index (AQI) of PM2.5 from 2013 to 2016. According to the correlation analysis between AQI and meteorological factors, the IBAM (Index Between Air pollution and Meteorology) is built by four factors (specific humidity, surface wind velocity, surface pressure change in 24 hours, and the difference of total temperature between two levels in the lower troposphere) from 2013 to 2016 in Chongqing. Then the past IBAM is attained by use of the EC numerical forecast products from 1 April 2013 to 31 〖JP2〗December 2016, and the prediction model of meteorological conditions is established by introducing the concepts of extreme weather events and Kmeans cluster analysis. The fitting curve equation between IBAM and AQI of 1day lagging can be used to calculate the forecast value of AQI; then according to the ranking standards of air quality, the forecasting accuracy of air pollution grades in 72h prediction reaches about 70% by a test with the samples of nearly two years (from 1 January 2017 to 1 September 2018). Through the error analysis of two air pollution events, the results show that the prediction of air pollution grades is relatively well when the meteorological condition is the major factor impacting the spread of the pollutants in atmosphere or the change of air pollution sources is not obvious (local accumulation as main air pollution mode). However, the prediction errors increase evidently when the change of air pollution sources is relatively remarkable because of upstream transportation. This forecast technique is applied in the realtime prediction services in the Chongqing Meteorological Observatory, which has important reference value for preventing heavy air pollution events and improving air quality in Chongqing.〖JP〗
A new technique for forecasting meteorological conditions of air pollution is developed by the analysis based on Air Quality Index (AQI) of PM2.5 from 2013 to 2016. According to the correlation analysis between AQI and meteorological factors, the IBAM (Index Between Air pollution and Meteorology) is built by four factors (specific humidity, surface wind velocity, surface pressure change in 24 hours, and the difference of total temperature between two levels in the lower troposphere) from 2013 to 2016 in Chongqing. Then the past IBAM is attained by use of the EC numerical forecast products from 1 April 2013 to 31 〖JP2〗December 2016, and the prediction model of meteorological conditions is established by introducing the concepts of extreme weather events and Kmeans cluster analysis. The fitting curve equation between IBAM and AQI of 1day lagging can be used to calculate the forecast value of AQI; then according to the ranking standards of air quality, the forecasting accuracy of air pollution grades in 72h prediction reaches about 70% by a test with the samples of nearly two years (from 1 January 2017 to 1 September 2018). Through the error analysis of two air pollution events, the results show that the prediction of air pollution grades is relatively well when the meteorological condition is the major factor impacting the spread of the pollutants in atmosphere or the change of air pollution sources is not obvious (local accumulation as main air pollution mode). However, the prediction errors increase evidently when the change of air pollution sources is relatively remarkable because of upstream transportation. This forecast technique is applied in the realtime prediction services in the Chongqing Meteorological Observatory, which has important reference value for preventing heavy air pollution events and improving air quality in Chongqing.〖JP〗
2020, 48(5):752-757.
Abstract:
Solar irradiance is closely related to the power generation of photovoltaic power plants, and the accuracy of irradiance forecast directly affects the accuracy of power generation forecast. Based on the reality of solar irradiance of the photovoltaic power plants and weather stations, WRF model irradiance forecast, the EC fine grid numerical forecast, and theoretical solar irradiance, a study of the revised solar irradiance forecast is carried out by means of stepwise regression. The conclusions are as follows: (1) the correlation between irradiance ratio and meteorological elements is better than that between irradiance and meteorological elements; (2) there are differences in meteorological factors that affect solar irradiance at different times, and a prediction model of solar irradiance at different times is established through the stepwise regression method; (3) in the case of nonclear weather, the RMSE of the regressed prediction irradiance is about 10% lower than that of the WRF model. The results have some application value in the new energy numerical forecasting service for photovoltaic power stations.
Solar irradiance is closely related to the power generation of photovoltaic power plants, and the accuracy of irradiance forecast directly affects the accuracy of power generation forecast. Based on the reality of solar irradiance of the photovoltaic power plants and weather stations, WRF model irradiance forecast, the EC fine grid numerical forecast, and theoretical solar irradiance, a study of the revised solar irradiance forecast is carried out by means of stepwise regression. The conclusions are as follows: (1) the correlation between irradiance ratio and meteorological elements is better than that between irradiance and meteorological elements; (2) there are differences in meteorological factors that affect solar irradiance at different times, and a prediction model of solar irradiance at different times is established through the stepwise regression method; (3) in the case of nonclear weather, the RMSE of the regressed prediction irradiance is about 10% lower than that of the WRF model. The results have some application value in the new energy numerical forecasting service for photovoltaic power stations.
2020, 48(5):758-765.
Abstract:
Pu’er is located in the southwest of Yunnan Province. Magma rocks are widely distributed. The geological structure of this area is not only complex, but also a typical red bed landslideprone area. The characteristics and the rainfall threshold curve of raininduced landslide disasters can be obtained by using the Caine threshold curve, rainfall intensity and duration, clustering analysis and other methods, by means of the data of rainfall and landslids from 2009 to 2014 over Pu’er, so as to provide a theoretical basis for the prediction and warning of rainfallinduced landslides in the red bed areas. The statistical analysis indicates: (1) The landslide hazards in the study area mainly focus on the Ailaoshan Mountain group, Wuliang Mountain group and Lancang Mountain group, and belong to the corresponding fault zones. (2) Landslide hazards account for 77.1% of the total, occurred most frequently from July to September. (3) Landslide hazards can be divided into the shortterm heavy rainfall type, midterm weak rainfall type and longterm weak rainfall type. The statistical analysis shows that there are 40 landslides without significant correlation with rainfall (0.7%). (4) Using the improved Caine model, it can be obtained that the rainfall threshold curves of landslides can be divided into four categories in the study area: I=85D－0.874, I=45D－0.811, I=27D－0.782, and I=12D－0.774. The minimum threshold is higher than the global threshold of Guzzetti, but lower than that of Caine, and the maximum threshold is higher than the threshold of landslides induced by typhoon rainfall in Fujian.
Pu’er is located in the southwest of Yunnan Province. Magma rocks are widely distributed. The geological structure of this area is not only complex, but also a typical red bed landslideprone area. The characteristics and the rainfall threshold curve of raininduced landslide disasters can be obtained by using the Caine threshold curve, rainfall intensity and duration, clustering analysis and other methods, by means of the data of rainfall and landslids from 2009 to 2014 over Pu’er, so as to provide a theoretical basis for the prediction and warning of rainfallinduced landslides in the red bed areas. The statistical analysis indicates: (1) The landslide hazards in the study area mainly focus on the Ailaoshan Mountain group, Wuliang Mountain group and Lancang Mountain group, and belong to the corresponding fault zones. (2) Landslide hazards account for 77.1% of the total, occurred most frequently from July to September. (3) Landslide hazards can be divided into the shortterm heavy rainfall type, midterm weak rainfall type and longterm weak rainfall type. The statistical analysis shows that there are 40 landslides without significant correlation with rainfall (0.7%). (4) Using the improved Caine model, it can be obtained that the rainfall threshold curves of landslides can be divided into four categories in the study area: I=85D－0.874, I=45D－0.811, I=27D－0.782, and I=12D－0.774. The minimum threshold is higher than the global threshold of Guzzetti, but lower than that of Caine, and the maximum threshold is higher than the threshold of landslides induced by typhoon rainfall in Fujian.
2020, 48(5):766-773.
Abstract:
Based on the observation data of 8 meteorological stations in the southern Hebei Province from 1962 to 2018, the characteristics and trends of climate change in summer maize growing season (June to September) are analyzed by the regression analysis, wavelet analysis and MannKendall test. The frequency of drought in the seedling stage of summer maize was 31.5%. After 1966, the climate in the seedling stage showed a humidification trend. A sudden change in climate humidification occurred around 1968 and 2009. The drywet changes during the entire analysis period (1962 to 2018) contained the periodic oscillations of 13 to 18 years and 5 to 8 years. The frequency of drought at the ear stage of summer corn was 40.3%, and the climate at the ear stage after 2006 showed a continuous aridity trend. A sudden change in climate aridification occurred around 1980 and 1997. The drywet changes in the entire analysis period contained the periodic oscillations of 15 to 22 years and 6 to 10 years. The frequency of drought during the flower and grain period of summer maize was 29.8%. After 1989, the climate during the flower and grain period showed a continuous aridification trend. It is possible that a sudden change of climate aridity occurred in 1992 and 2002. The frequency of drought in the summer corn growing season is about 30%. The climate in the growing season showed a trend of aridification, especially after 1997, and there experienced abrupt climate aridification around 1996. The above results are expected to provide a theoretical basis for drought disaster monitoring, prediction, early warning and prevention.
Based on the observation data of 8 meteorological stations in the southern Hebei Province from 1962 to 2018, the characteristics and trends of climate change in summer maize growing season (June to September) are analyzed by the regression analysis, wavelet analysis and MannKendall test. The frequency of drought in the seedling stage of summer maize was 31.5%. After 1966, the climate in the seedling stage showed a humidification trend. A sudden change in climate humidification occurred around 1968 and 2009. The drywet changes during the entire analysis period (1962 to 2018) contained the periodic oscillations of 13 to 18 years and 5 to 8 years. The frequency of drought at the ear stage of summer corn was 40.3%, and the climate at the ear stage after 2006 showed a continuous aridity trend. A sudden change in climate aridification occurred around 1980 and 1997. The drywet changes in the entire analysis period contained the periodic oscillations of 15 to 22 years and 6 to 10 years. The frequency of drought during the flower and grain period of summer maize was 29.8%. After 1989, the climate during the flower and grain period showed a continuous aridification trend. It is possible that a sudden change of climate aridity occurred in 1992 and 2002. The frequency of drought in the summer corn growing season is about 30%. The climate in the growing season showed a trend of aridification, especially after 1997, and there experienced abrupt climate aridification around 1996. The above results are expected to provide a theoretical basis for drought disaster monitoring, prediction, early warning and prevention.
20 Analysis of Meteorological Affecting Factors During Flowering Period of Autumn Osmanthus in Chengdu
2020, 48(5):774-778.
Abstract:
Correlation analysis and factor analysis are used to study the relationship between the flowering of autumn osmanthus and the meteorological factors four weeks before flowering， based on the osmanthus phenology data and the meteorological data from 2004 to 2017 in Chengdu. The results show: (1) There is a negative correlation between the flowering stage and the average minimum temperature and precipitation in one week before flowering. The higher the minimum temperature in the week before flowering, the more abundant the precipitation, and the earlier the flowering is. (2) The main components of temperature and light and rainfall are extracted by factor analysis. The main components of temperature and light are most closely related to the flowering period of autumn osmanthus, and temperature played a leading role in the flowering of autumn osmanthus. (3) A score model for the comprehensive evaluation of flowering period is established by using the variance contribution rate of the first principal component and the second principal component. The period of 4 weeks before flowering (from late July to midAugust) is an important period for flowering, and also for the completion of flower bud differentiation. The comprehensive application of correlation analysis and factor analysis can better reflect the relationship between meteorological factors and the flowering of autumn osmanthus, reveal the influence of meteorological factors on the flowering, and provide scientific and technological supports for the meteorological service for autumn osmanthus flowering in Chengdu.
Correlation analysis and factor analysis are used to study the relationship between the flowering of autumn osmanthus and the meteorological factors four weeks before flowering， based on the osmanthus phenology data and the meteorological data from 2004 to 2017 in Chengdu. The results show: (1) There is a negative correlation between the flowering stage and the average minimum temperature and precipitation in one week before flowering. The higher the minimum temperature in the week before flowering, the more abundant the precipitation, and the earlier the flowering is. (2) The main components of temperature and light and rainfall are extracted by factor analysis. The main components of temperature and light are most closely related to the flowering period of autumn osmanthus, and temperature played a leading role in the flowering of autumn osmanthus. (3) A score model for the comprehensive evaluation of flowering period is established by using the variance contribution rate of the first principal component and the second principal component. The period of 4 weeks before flowering (from late July to midAugust) is an important period for flowering, and also for the completion of flower bud differentiation. The comprehensive application of correlation analysis and factor analysis can better reflect the relationship between meteorological factors and the flowering of autumn osmanthus, reveal the influence of meteorological factors on the flowering, and provide scientific and technological supports for the meteorological service for autumn osmanthus flowering in Chengdu.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.