Volume 51,Issue 4,2023 Table of Contents
WANG Haofei
,
ZHANG Peng
,
SHANG Jian
,
YIN Dekui
,
LI Zhengqiang
,
WU Shengli
,
XU Hanlie
,
GU Songyan
,
HU Xiuqing
2023, 51(4):455-462.
DOI: 10.19517/j.1671-6345.20220216
Abstract:
Accurate measurement of the radiative properties of clouds and aerosols is of great significance to global climate change and numerical weather prediction. The polarization payload mounted on the Fengyun-3 precipitation satellite is the first domestic multiangle polarization imager (PMAI) with short-wave infrared channels. It is planned to be launched at the beginning of 2023, providing important support for the aerosol-cloud-precipitation observation chain. The instrument operates in a non-sun-synchronized inclined orbit and provides images with a spatial resolution of 3 km (sub-satellite) and a width of 700 km. The observation channels of PMAI include 1030 nm, 1370 nm, and 1640 nm polarization channels and corresponding non-polarization channels, which can provide observation information from 14 angles. PMAI will utilize onorbit vicarious calibration of natural targets and cross-calibration of instruments on the same platform to achieve 5% radiometric accuracy. PMAI has the unique advantage of characterizing clouds and aerosols. The multi-angle polarization measurement of the new short-wave infrared channel can optimize cloud phase state identification and cloud micro-physical parameter inversion, as well as ground-air decoupling of aerosols, and at the same time, characterize surface directional reflection characteristics. The unique observation geometry of non-sun-synchronous orbits can make full use of the distribution characteristics of earth-atmosphere radiation with scattering angles for parameter inversion. In addition, PMAI can optimize cloud and aerosol retrieval in conjunction with the observational information of the visible, near-infrared and thermal infrared channels of the mid-resolution spectral imager on the same platform.
Accurate measurement of the radiative properties of clouds and aerosols is of great significance to global climate change and numerical weather prediction. The polarization payload mounted on the Fengyun-3 precipitation satellite is the first domestic multiangle polarization imager (PMAI) with short-wave infrared channels. It is planned to be launched at the beginning of 2023, providing important support for the aerosol-cloud-precipitation observation chain. The instrument operates in a non-sun-synchronized inclined orbit and provides images with a spatial resolution of 3 km (sub-satellite) and a width of 700 km. The observation channels of PMAI include 1030 nm, 1370 nm, and 1640 nm polarization channels and corresponding non-polarization channels, which can provide observation information from 14 angles. PMAI will utilize onorbit vicarious calibration of natural targets and cross-calibration of instruments on the same platform to achieve 5% radiometric accuracy. PMAI has the unique advantage of characterizing clouds and aerosols. The multi-angle polarization measurement of the new short-wave infrared channel can optimize cloud phase state identification and cloud micro-physical parameter inversion, as well as ground-air decoupling of aerosols, and at the same time, characterize surface directional reflection characteristics. The unique observation geometry of non-sun-synchronous orbits can make full use of the distribution characteristics of earth-atmosphere radiation with scattering angles for parameter inversion. In addition, PMAI can optimize cloud and aerosol retrieval in conjunction with the observational information of the visible, near-infrared and thermal infrared channels of the mid-resolution spectral imager on the same platform.
2023, 51(4):463-472.
DOI: 10.19517/j.1671-6345.20220236
Abstract:
China needs more cloud data in the icing meteorological conditions. The icing conditions in Appendix C of Part 25 of the Civil Aviation Regulations of China can only be copied from the American Aviation Regulations. There needs to have more research on the compliance analysis method of Appendix C for the icing cloud data obtained from flight detection. The icing conditions in Appendix C were formed in the late 1940s. The detection methods at that time were quite different from the data forms obtained by advanced detection instruments today. Therefore, the specific definitions of the icing conditions parameters in Appendix C are first clarified, and the data processing and analysis methods are studied according to the highresolution characteristics of the data measured by the current detection instruments. Finally, based on this method, the ice meteorological observation data of Anqing are analyzed. From the analysis results, this method can clearly show the basic characteristics of the icing conditions of the detected cloud and its compliance with Appendix C.
China needs more cloud data in the icing meteorological conditions. The icing conditions in Appendix C of Part 25 of the Civil Aviation Regulations of China can only be copied from the American Aviation Regulations. There needs to have more research on the compliance analysis method of Appendix C for the icing cloud data obtained from flight detection. The icing conditions in Appendix C were formed in the late 1940s. The detection methods at that time were quite different from the data forms obtained by advanced detection instruments today. Therefore, the specific definitions of the icing conditions parameters in Appendix C are first clarified, and the data processing and analysis methods are studied according to the highresolution characteristics of the data measured by the current detection instruments. Finally, based on this method, the ice meteorological observation data of Anqing are analyzed. From the analysis results, this method can clearly show the basic characteristics of the icing conditions of the detected cloud and its compliance with Appendix C.
2023, 51(4):473-479.
DOI: 10.19517/j.1671-6345.20220295
Abstract:
The lack of snow parameters such as snow density and snow pressure is one of the difficulties in the study of snow disaster prevention in the Southern China. It is a helpful supplement to the existing snow monitoring data to invert the snow density of the station and its surroundings through historical ground snow meteorological observation data. Based on the daily meteorological observation data of 76 stations in Hubei Province, this paper analyzes and selects eight independent variable factors affecting snow density, such as the number of snow days, snow depth, air temperature and sunshine, and constructs a Random Forest (RF) regression model of snow density. Through the inversion data of the RF model, the distributions of snow density and snow pressure in Hubei Province are analyzed. The results show that: (1) The root mean square error predicted by the snow density RF model is about 0.04 g/cm3, which can be used for the inversion of snow density data in Hubei Province. (2) The average snow density in Hubei Province is between 0.14 and 0.20 g/cm3, and is divided into east and west regions based on the value of 0.17 g/cm3, with the larger snow density in the eastern region. (3) The maximum snow pressure in Hubei Province in recent 60 years is between 1.3 and 6.7 g/cm2. The distributions of maximum snow pressure in different return periods have two high-value areas in northwest and east of Hubei Province, and the basic snow pressure value in the northcentral part of the east of Hubei Province is greater.
The lack of snow parameters such as snow density and snow pressure is one of the difficulties in the study of snow disaster prevention in the Southern China. It is a helpful supplement to the existing snow monitoring data to invert the snow density of the station and its surroundings through historical ground snow meteorological observation data. Based on the daily meteorological observation data of 76 stations in Hubei Province, this paper analyzes and selects eight independent variable factors affecting snow density, such as the number of snow days, snow depth, air temperature and sunshine, and constructs a Random Forest (RF) regression model of snow density. Through the inversion data of the RF model, the distributions of snow density and snow pressure in Hubei Province are analyzed. The results show that: (1) The root mean square error predicted by the snow density RF model is about 0.04 g/cm3, which can be used for the inversion of snow density data in Hubei Province. (2) The average snow density in Hubei Province is between 0.14 and 0.20 g/cm3, and is divided into east and west regions based on the value of 0.17 g/cm3, with the larger snow density in the eastern region. (3) The maximum snow pressure in Hubei Province in recent 60 years is between 1.3 and 6.7 g/cm2. The distributions of maximum snow pressure in different return periods have two high-value areas in northwest and east of Hubei Province, and the basic snow pressure value in the northcentral part of the east of Hubei Province is greater.
2023, 51(4):480-488.
DOI: 10.19517/j.1671-6345.20220165
Abstract:
Based on the ERA-Interim reanalysis data, an intensity index of the South Branch Trough (SBT) is defined by the result of the objective identification method of the SBT. The relationships between the interannual variations of the SBT intensity and the precipitation, atmospheric circulation, and water vapour transport during 1980-2019 are investigated in this study. The results show: (1) The intensity index of the SBT mainly characterizes interannual variations with the quasi-4-year cycle. (2) The sea surface temperature in the central equatorial Pacific is an important factor affecting the interannual variations of the SBT, which has a significant negative correlation with the intensity of the SBT, especially the SST over the Nino 3 region. (3) When the intensity of the SBT is stronger, the precipitation from southern Yunnan to South China is more than normal, especially in Guangdong, southern Hunan, southern Jiangxi, and southern Fujian, which is 30 mm more than normal. When the intensity of SBT is weaker, the precipitation in Southwest China to South China is less than normal. In particular, the precipitation in central Guangdong and Guangxi is over 30 mm less than normal. (4) There are two water vapour transport paths with strong intensity of SBT. One is the water vapour conveying belt with anomalously strong westerly wind extending from the north of the equator to 10°N and 60°E to the Philippines. The other branch is located near 20°N, and the southwest airflow in front of the SBT transports the water vapour from the Bay of Bengal area to China, which is the main water vapour channel of Southwest and South China in winter.
Based on the ERA-Interim reanalysis data, an intensity index of the South Branch Trough (SBT) is defined by the result of the objective identification method of the SBT. The relationships between the interannual variations of the SBT intensity and the precipitation, atmospheric circulation, and water vapour transport during 1980-2019 are investigated in this study. The results show: (1) The intensity index of the SBT mainly characterizes interannual variations with the quasi-4-year cycle. (2) The sea surface temperature in the central equatorial Pacific is an important factor affecting the interannual variations of the SBT, which has a significant negative correlation with the intensity of the SBT, especially the SST over the Nino 3 region. (3) When the intensity of the SBT is stronger, the precipitation from southern Yunnan to South China is more than normal, especially in Guangdong, southern Hunan, southern Jiangxi, and southern Fujian, which is 30 mm more than normal. When the intensity of SBT is weaker, the precipitation in Southwest China to South China is less than normal. In particular, the precipitation in central Guangdong and Guangxi is over 30 mm less than normal. (4) There are two water vapour transport paths with strong intensity of SBT. One is the water vapour conveying belt with anomalously strong westerly wind extending from the north of the equator to 10°N and 60°E to the Philippines. The other branch is located near 20°N, and the southwest airflow in front of the SBT transports the water vapour from the Bay of Bengal area to China, which is the main water vapour channel of Southwest and South China in winter.
2023, 51(4):489-498.
DOI: 10.19517/j.1671-6345.20220274
Abstract:
Based on the monthly temperature (average, maximum and minimum), precipitation and wind speed data observed at 50 stations on the Qinghai Plateau from 1961 to 2020, the temporal and spatial distribution and interdecadal trend turning of climate change on the Qinghai Plateau are analyzed by using piecewise linear fitting model (PLFIM) and climate tendency rate. The results show that: (1) the temperature (average, maximum and minimum) of the Qinghai Plateau showed a significant upward trend from 1961 to 2020, among which the rate of warming of the minimum temperature was particularly obvious, with an average increase of 0.62 ℃ per decade. Precipitation showed a fluctuating upward trend, and increased significantly after entering the 21st century, with a rate of 39.9 mm·(10a)-1. Wind speed showed a decreasing trend, among which the wind speed at Mangya Station was the most obvious, with a decrease rate of -0.56 m·s-1·(10a)-1. (2) The average and maximum temperatures of the Qinghai Plateau experienced interdecadal trend turning in 1972 and 1983, the third turning in maximum temperature occurred in 2009, and no significant interdecadal trend turning occurred in minimum temperature. Interdecadal trend turning in precipitation occurred in 1972, 1983 and 2000. The interdecadal trend turning of wind speed occurred in 1971, 1998 and 2009. (3) Compared with the previous climate state (1961-1990), the annual average, maximum and minimum temperatures increased by 1.16 ℃, 1.22 ℃ and 1.81 ℃ respectively, from 1991 to 2020, and the probability density distribution was flatter, indicating that the temperature dispersion was greater and the climate instability was enhanced. (4) Under the background of global warming, the average temperature and precipitation on the Qinghai Plateau increased in the past 60 years, with the average temperature increasing rate much greater than those of the global, China and the same latitude regions. Interannual fluctuations in precipitation were large, but the overall trend was increasing.
Based on the monthly temperature (average, maximum and minimum), precipitation and wind speed data observed at 50 stations on the Qinghai Plateau from 1961 to 2020, the temporal and spatial distribution and interdecadal trend turning of climate change on the Qinghai Plateau are analyzed by using piecewise linear fitting model (PLFIM) and climate tendency rate. The results show that: (1) the temperature (average, maximum and minimum) of the Qinghai Plateau showed a significant upward trend from 1961 to 2020, among which the rate of warming of the minimum temperature was particularly obvious, with an average increase of 0.62 ℃ per decade. Precipitation showed a fluctuating upward trend, and increased significantly after entering the 21st century, with a rate of 39.9 mm·(10a)-1. Wind speed showed a decreasing trend, among which the wind speed at Mangya Station was the most obvious, with a decrease rate of -0.56 m·s-1·(10a)-1. (2) The average and maximum temperatures of the Qinghai Plateau experienced interdecadal trend turning in 1972 and 1983, the third turning in maximum temperature occurred in 2009, and no significant interdecadal trend turning occurred in minimum temperature. Interdecadal trend turning in precipitation occurred in 1972, 1983 and 2000. The interdecadal trend turning of wind speed occurred in 1971, 1998 and 2009. (3) Compared with the previous climate state (1961-1990), the annual average, maximum and minimum temperatures increased by 1.16 ℃, 1.22 ℃ and 1.81 ℃ respectively, from 1991 to 2020, and the probability density distribution was flatter, indicating that the temperature dispersion was greater and the climate instability was enhanced. (4) Under the background of global warming, the average temperature and precipitation on the Qinghai Plateau increased in the past 60 years, with the average temperature increasing rate much greater than those of the global, China and the same latitude regions. Interannual fluctuations in precipitation were large, but the overall trend was increasing.
2023, 51(4):499-509.
DOI: 10.19517/j.1671-6345.20220173
Abstract:
Based on the meteorological surface observation data from 1999 to 2019, the evolution characteristics of sand-dust weather frequency in the main sand sources in East Asia (Mongolia, Xinjiang and Inner Mongolia) and the downstream areas in China are analyzed. The results show that the most severe sand-dust weather is in Mongolia, which shows an increasing trend, with the highest numbers of sand, sandstorm and strong sandstorm days in all of the regions. The frequency of sand-dust weather is reduced in China and increases rapidly in Xinjiang; moreover, it obviously reduces in Inner Mongolia and the downstream area. In Xinjiang, the frequency of dust weather is the highest, and shows an obvious increasing trend with linear tendency in the past 21 years. In Inner Mongolia, the sand blowing weather occure more frequently than other sand-dust weather, while the strong sandstorm is relatively less. In addition, all kinds of sand-dust weather are reduced. In the downstream area of China, dust and sand weather occurs frequently and decreases slightly. At the same time, sandstorms and strong sandstorms rarely occur. According to the interannual variations of sand-dust weather in China, 1999-2004 is the peak period, and 2005-2019 is obviously reduced, with 2010-2014 showing the fastest decline. The contribution of the sand sources to the total number of sanddust weather days in China has increased continuously, from 39% at the beginning of 2000 to 71% after 2015. As sand sources, Mongolia’s contribution to sand-dust weather has increased, while Inner Mongolia’s has weakened. There is a significant reduction in the number of severe dust events that can affect and spread to the downstream areas of China and other downstream countries.
Based on the meteorological surface observation data from 1999 to 2019, the evolution characteristics of sand-dust weather frequency in the main sand sources in East Asia (Mongolia, Xinjiang and Inner Mongolia) and the downstream areas in China are analyzed. The results show that the most severe sand-dust weather is in Mongolia, which shows an increasing trend, with the highest numbers of sand, sandstorm and strong sandstorm days in all of the regions. The frequency of sand-dust weather is reduced in China and increases rapidly in Xinjiang; moreover, it obviously reduces in Inner Mongolia and the downstream area. In Xinjiang, the frequency of dust weather is the highest, and shows an obvious increasing trend with linear tendency in the past 21 years. In Inner Mongolia, the sand blowing weather occure more frequently than other sand-dust weather, while the strong sandstorm is relatively less. In addition, all kinds of sand-dust weather are reduced. In the downstream area of China, dust and sand weather occurs frequently and decreases slightly. At the same time, sandstorms and strong sandstorms rarely occur. According to the interannual variations of sand-dust weather in China, 1999-2004 is the peak period, and 2005-2019 is obviously reduced, with 2010-2014 showing the fastest decline. The contribution of the sand sources to the total number of sanddust weather days in China has increased continuously, from 39% at the beginning of 2000 to 71% after 2015. As sand sources, Mongolia’s contribution to sand-dust weather has increased, while Inner Mongolia’s has weakened. There is a significant reduction in the number of severe dust events that can affect and spread to the downstream areas of China and other downstream countries.
2023, 51(4):510-519.
DOI: 10.19517/j.1671-6345.20220292
Abstract:
In order to explore the changes in visibility in East China, using visibility data from 1973 to 2020, meteorological elements and pollutant concentration data from 2014 to 2019, the temporal and spatial variation characteristics and influencing factors of visibility are analyzed by using trend analysis, empirical orthogonal function (EOF) decomposition, and correlation analysis. The results show that from 1973 to 2020, the visibility shows a significant (p<0.01) decreasing trend, and the trend rate of change is -1.315 km/10a. There are differences between seasons. The decreasing rates of visibility in summer and autumn are 1.681 km/10a and 1.443 km/10a, respectively. The decrease rates in winter and spring are 1.092 km/10a and 1.091 km/10a, respectively. The visibility shows a significant (p<0.01) decreasing trend from 1973 to 2012, and the change tendency rate is -1.204 km/10a. The visibility shows an insignificant (p>0.05) increasing trend during 2013-2020, and the change tendency rate is 2.229 km/10a. Visibility has improved significantly in the past eight years (2013-2020). Visibility is better in the south and north of East China but poorer in the middle. The first mode of EOF decomposition shows that the overall change trend of visibility in East China is consistent. The second mode has obvious regional differences. Visibility is significantly negatively correlated with relative humidity, PM2.5, PM10, SO2, and NO2, and positively correlated with O3 mass concentration. Relative humidity is the most important factor affecting visibility reduction, followed by PM2.5 mass concentration. The relationship between temperature and pressure, and visibility is strong uncertainty.
In order to explore the changes in visibility in East China, using visibility data from 1973 to 2020, meteorological elements and pollutant concentration data from 2014 to 2019, the temporal and spatial variation characteristics and influencing factors of visibility are analyzed by using trend analysis, empirical orthogonal function (EOF) decomposition, and correlation analysis. The results show that from 1973 to 2020, the visibility shows a significant (p<0.01) decreasing trend, and the trend rate of change is -1.315 km/10a. There are differences between seasons. The decreasing rates of visibility in summer and autumn are 1.681 km/10a and 1.443 km/10a, respectively. The decrease rates in winter and spring are 1.092 km/10a and 1.091 km/10a, respectively. The visibility shows a significant (p<0.01) decreasing trend from 1973 to 2012, and the change tendency rate is -1.204 km/10a. The visibility shows an insignificant (p>0.05) increasing trend during 2013-2020, and the change tendency rate is 2.229 km/10a. Visibility has improved significantly in the past eight years (2013-2020). Visibility is better in the south and north of East China but poorer in the middle. The first mode of EOF decomposition shows that the overall change trend of visibility in East China is consistent. The second mode has obvious regional differences. Visibility is significantly negatively correlated with relative humidity, PM2.5, PM10, SO2, and NO2, and positively correlated with O3 mass concentration. Relative humidity is the most important factor affecting visibility reduction, followed by PM2.5 mass concentration. The relationship between temperature and pressure, and visibility is strong uncertainty.
2023, 51(4):520-531.
DOI: 10.19517/j.1671-6345.20220258
Abstract:
In August 2021, extremely unusual precipitation in the eastern part of Southwest China reached the second highest next to 1998 since 1961. Based on daily precipitation and monthly ERA5 reanalysis data during 1961-2021, the main water vapour transport conditions and water vapour sources, along with the abnormal atmospheric circulation characteristics for anomalous more than normal precipitation in August 2021 over the eastern part of SW China, are analyzed. The results show that the net inflow of water vapour in the eastern part of southwest China in August 2021 is mainly from the mid-lower troposphere, with the largest contribution from the lowest layer. In August 2021, the water vapour transport pathway is the most unique one, different from the main trajectory and contribution from the southern pathway. In August 2021, the abnormal precipitation in the eastern part of southwest China is closely related to the abnormal atmospheric circulation, mainly reflected in the 500 hPa with blocking system over the Ural Mountains and the sea of Okhotsk resistance, and the abnormally active mid-latitude low system (i.e. Northeast cold vortex), the weak Indian low pressure and the western subtropical high abnormal westward extension and strong intensity. The favourable water vapour transport guided by the atmospheric circulation system results in more abnormal precipitation in the eastern part of Southwest China. Persistent warming of the Indian Ocean is likely an important external forcing factor maintaining the continuously intensified Pacific subtropical high in August 2021, while the abnormal strength of the Okhotsk high in the same period could be related to the abnormal warming of the Northwest Pacific SST. As a result, they play a positive role in the excessive precipitation in the Southwest China region.
In August 2021, extremely unusual precipitation in the eastern part of Southwest China reached the second highest next to 1998 since 1961. Based on daily precipitation and monthly ERA5 reanalysis data during 1961-2021, the main water vapour transport conditions and water vapour sources, along with the abnormal atmospheric circulation characteristics for anomalous more than normal precipitation in August 2021 over the eastern part of SW China, are analyzed. The results show that the net inflow of water vapour in the eastern part of southwest China in August 2021 is mainly from the mid-lower troposphere, with the largest contribution from the lowest layer. In August 2021, the water vapour transport pathway is the most unique one, different from the main trajectory and contribution from the southern pathway. In August 2021, the abnormal precipitation in the eastern part of southwest China is closely related to the abnormal atmospheric circulation, mainly reflected in the 500 hPa with blocking system over the Ural Mountains and the sea of Okhotsk resistance, and the abnormally active mid-latitude low system (i.e. Northeast cold vortex), the weak Indian low pressure and the western subtropical high abnormal westward extension and strong intensity. The favourable water vapour transport guided by the atmospheric circulation system results in more abnormal precipitation in the eastern part of Southwest China. Persistent warming of the Indian Ocean is likely an important external forcing factor maintaining the continuously intensified Pacific subtropical high in August 2021, while the abnormal strength of the Okhotsk high in the same period could be related to the abnormal warming of the Northwest Pacific SST. As a result, they play a positive role in the excessive precipitation in the Southwest China region.
2023, 51(4):532-540.
DOI: 10.19517/j.1671-6345.20220262
Abstract:
An event of continuous rainy weather occurred in Zhejiang Province in February 2019. The characteristics of atmospheric circulation are analyzed based on conventional observed data, FY-2E infrared satellite data, NCEP and ERAInterim reanalysis data. The results show: (1) The polar vortex shrinked near the North Pole in February 2019, which caused positive temperature and southwest wind anomaly at 700 hPa and 850 hPa; the westerly jet on the upper troposphere was norther and stronger than usual. The intensity and location of the jet changed ahead of rainfall. (2) There were two water vapour transport channels during continuous rainy weather, which were from the Tibet Plateau and Bay of Bengal vapour channel, Indo-China Peninsula and northern South China Sea. There will be heavy rain when both water vapour transport channels are strong in Zhejiang Province, and it can be clearly seen from the infrared cloud image. (3) The wet Q Vector convergence area at 700 hPa overlapped with the 0 m·s-1 longitudinal wind area at 850 hPa corresponded well with heavy rain area. There were large pseudoequivalent potential temperatures and water-vapour flux horizontal gradient in the lower troposphere, water vapour transport belt was under it.
An event of continuous rainy weather occurred in Zhejiang Province in February 2019. The characteristics of atmospheric circulation are analyzed based on conventional observed data, FY-2E infrared satellite data, NCEP and ERAInterim reanalysis data. The results show: (1) The polar vortex shrinked near the North Pole in February 2019, which caused positive temperature and southwest wind anomaly at 700 hPa and 850 hPa; the westerly jet on the upper troposphere was norther and stronger than usual. The intensity and location of the jet changed ahead of rainfall. (2) There were two water vapour transport channels during continuous rainy weather, which were from the Tibet Plateau and Bay of Bengal vapour channel, Indo-China Peninsula and northern South China Sea. There will be heavy rain when both water vapour transport channels are strong in Zhejiang Province, and it can be clearly seen from the infrared cloud image. (3) The wet Q Vector convergence area at 700 hPa overlapped with the 0 m·s-1 longitudinal wind area at 850 hPa corresponded well with heavy rain area. There were large pseudoequivalent potential temperatures and water-vapour flux horizontal gradient in the lower troposphere, water vapour transport belt was under it.
2023, 51(4):541-550.
DOI: 10.19517/j.1671-6345.20220281
Abstract:
This paper compares and analyzes different types of strong convective weather under the background of the North China cold vortex that occurred in two similar circulation situations in Shandong based on ground and highaltitude observations, NCEP 1°×1° Reanalysis data and Doppler radar data. The results show that the strong convection weather process on 14 June 2016 (6·14) was dominated by thunderstorm gale and short-term heavy precipitation, which occurred in the low-level vertical wind shear, and there was relatively deep warm and moist advection in the middle and lower troposphere (400 to 900 hPa) with abundant water vapour transport. At the same time, the height of the 0 ℃ and -20 ℃ layers would rise, which was conducive to short-term heavy precipitation but not hail generation. The strong convective weather process on 13 June 2018 (6·13) was dominated by thunderstorm gale and hail, which occurred in strong conditional instability layers and strong low-level vertical wind shear, and the simultaneous enhancement of 400 to 500 hPa cold advection and low-level warm advection was conducive to the further increase of the vertical decline rate of temperature in the middle troposphere, resulting in the further decline of -20 ℃ to -30 ℃ layer, and contributing to the occurrence environment of the large hail. The “6·14” strong convective weather process was triggered by the surface convergence line, and the “6·13” strong convective weather process was triggered by the front. The strong reflectivity factor of the “6·14” strong convective weather process was low in height, and there was no obvious high-hanging strong echo structure, which was conducive to the occurrence of short-term heavy precipitation, and the “6·13” strong convective weather process had the characteristics of the dense single structure and obvious high hanging strong echo structure. Therefore, the convective intensity of the “6·13” strong convective weather process was stronger and more prone to hail.
This paper compares and analyzes different types of strong convective weather under the background of the North China cold vortex that occurred in two similar circulation situations in Shandong based on ground and highaltitude observations, NCEP 1°×1° Reanalysis data and Doppler radar data. The results show that the strong convection weather process on 14 June 2016 (6·14) was dominated by thunderstorm gale and short-term heavy precipitation, which occurred in the low-level vertical wind shear, and there was relatively deep warm and moist advection in the middle and lower troposphere (400 to 900 hPa) with abundant water vapour transport. At the same time, the height of the 0 ℃ and -20 ℃ layers would rise, which was conducive to short-term heavy precipitation but not hail generation. The strong convective weather process on 13 June 2018 (6·13) was dominated by thunderstorm gale and hail, which occurred in strong conditional instability layers and strong low-level vertical wind shear, and the simultaneous enhancement of 400 to 500 hPa cold advection and low-level warm advection was conducive to the further increase of the vertical decline rate of temperature in the middle troposphere, resulting in the further decline of -20 ℃ to -30 ℃ layer, and contributing to the occurrence environment of the large hail. The “6·14” strong convective weather process was triggered by the surface convergence line, and the “6·13” strong convective weather process was triggered by the front. The strong reflectivity factor of the “6·14” strong convective weather process was low in height, and there was no obvious high-hanging strong echo structure, which was conducive to the occurrence of short-term heavy precipitation, and the “6·13” strong convective weather process had the characteristics of the dense single structure and obvious high hanging strong echo structure. Therefore, the convective intensity of the “6·13” strong convective weather process was stronger and more prone to hail.
ZHOU Houfu
,
CHEN Jian
,
YAO Yun
,
SHAN Naichao
,
WU Yuyan
,
HUANG Yong
,
LU Yanyu
,
WU Wenyu
,
HOU Can
2023, 51(4):551-561.
DOI: 10.19517/j.1671-6345.20220214
Abstract:
Based on the automatic weather station, Doppler radar, FY4A, ECMWF model and NCEP reanalysis data, the extraordinary rain process from July 17 to 19, 2020, is analyzed. The results are as followings. The extraordinary rain occurred near Dabie Mountain and Lujiang County in Anhui Province, caused by the quasistationary mesoscale convective system (MCS) and the quasistationary vortex cell in MCS. The mesoscale cyclonic disturbance was composed of the shear line and cyclone. Under the background of high energy and strong instability, the extraordinary rain was caused by the mesoscale cyclone in the middle and east. In mesoscale cyclone propagation, the cell continuously produced, merged and strengthened, and moved slowly. The factors such as jet stream, convergence, dry intrusion and vertical circulation played an important role in the development and evolution of organized MCS. The southwest jet from the southern side of the lowlevel shear line to South China transported water vapour to the Yangtze and Huaihe River Basin, where there was strong convergence. There were jets at the high, low, and ultra-low levels, and the coupling of high and lowlevel jets intensified the strong development of MCS. The surface convergence line was the trigger mechanism of MCS in the early stage. With the invasion of dry and cold air, the baroclinity of the atmosphere and the convective instability of MCS were increased. The surface convergence line was the trigger mechanism of MCS in the early stage. With the invasion of dry and cold air, the baroclinity of the atmosphere and the convective instability of MCS were increased. There were vertical circulation circles on both sides of the Meiyu front, that was, the convective heating between the convection and the upper jet generated thermal wind adjustment at the entrance of the upper jet stream to maintain the development and evolution of the Meiyu front, and the strong ascending and descending motion promoted the strengthening and falling of MCS and continuous occurrence of rain. The terrain uplift of Dabie Mountain and the narrow pipe effect in the upper reaches induced extraordinary rain in the two places.
Based on the automatic weather station, Doppler radar, FY4A, ECMWF model and NCEP reanalysis data, the extraordinary rain process from July 17 to 19, 2020, is analyzed. The results are as followings. The extraordinary rain occurred near Dabie Mountain and Lujiang County in Anhui Province, caused by the quasistationary mesoscale convective system (MCS) and the quasistationary vortex cell in MCS. The mesoscale cyclonic disturbance was composed of the shear line and cyclone. Under the background of high energy and strong instability, the extraordinary rain was caused by the mesoscale cyclone in the middle and east. In mesoscale cyclone propagation, the cell continuously produced, merged and strengthened, and moved slowly. The factors such as jet stream, convergence, dry intrusion and vertical circulation played an important role in the development and evolution of organized MCS. The southwest jet from the southern side of the lowlevel shear line to South China transported water vapour to the Yangtze and Huaihe River Basin, where there was strong convergence. There were jets at the high, low, and ultra-low levels, and the coupling of high and lowlevel jets intensified the strong development of MCS. The surface convergence line was the trigger mechanism of MCS in the early stage. With the invasion of dry and cold air, the baroclinity of the atmosphere and the convective instability of MCS were increased. The surface convergence line was the trigger mechanism of MCS in the early stage. With the invasion of dry and cold air, the baroclinity of the atmosphere and the convective instability of MCS were increased. There were vertical circulation circles on both sides of the Meiyu front, that was, the convective heating between the convection and the upper jet generated thermal wind adjustment at the entrance of the upper jet stream to maintain the development and evolution of the Meiyu front, and the strong ascending and descending motion promoted the strengthening and falling of MCS and continuous occurrence of rain. The terrain uplift of Dabie Mountain and the narrow pipe effect in the upper reaches induced extraordinary rain in the two places.
2023, 51(4):562-572.
DOI: 10.19517/j.1671-6345.20220286
Abstract:
Using conventional meteorological observation data, lightning location data, ERA5 reanalysis data and dualpolarization radar data, an extreme “thunder snow” process in Northwest Shandong Province from 6 to 7 November 2021 is analyzed. The results show: (1) Thunderstorm and snowfall occurred 150 km behind the cold front, which belonged to the cold front type elevated convection in winter. The duration and frequency of lightning had a good corresponding relationship with the snowfall. (2) The circulation pattern was characterized by “cold at the bottom and warm at the top”. The lower layer was the “cold layer” behind the cold front, and the “warm layer” formed by the southwest warm and humid airflow near 800 hPa. The southwest lowlevel jet and the northeast wind ultralowlevel jet were exceptionally strong, which not only provided sufficient water vapour for the convective generation but also made the deep vertical wind shear reach 6.7×10-3 s-1, which was conducive to increasing the stratification instability. (3) Before the occurrence of “thunder snow”, the atmosphere over Northwest Shandong was convective instability. The cold surface gradually thickened with the invasion of cold air, and there was conditional symmetric instability near the cold front over Northwest Shandong. The mesoscale vortex at 800 hPa triggered convection above the inversion layer and generated lightning. (4) It could be seen from the dualpolarization radar products that there were obvious twolayer echoes around the station when thunder snow occurred, and the concentration of ice phase particles at -10 ℃ layer height (about 600 hPa) was relatively large, which might be one of the lightning mechanism.
Using conventional meteorological observation data, lightning location data, ERA5 reanalysis data and dualpolarization radar data, an extreme “thunder snow” process in Northwest Shandong Province from 6 to 7 November 2021 is analyzed. The results show: (1) Thunderstorm and snowfall occurred 150 km behind the cold front, which belonged to the cold front type elevated convection in winter. The duration and frequency of lightning had a good corresponding relationship with the snowfall. (2) The circulation pattern was characterized by “cold at the bottom and warm at the top”. The lower layer was the “cold layer” behind the cold front, and the “warm layer” formed by the southwest warm and humid airflow near 800 hPa. The southwest lowlevel jet and the northeast wind ultralowlevel jet were exceptionally strong, which not only provided sufficient water vapour for the convective generation but also made the deep vertical wind shear reach 6.7×10-3 s-1, which was conducive to increasing the stratification instability. (3) Before the occurrence of “thunder snow”, the atmosphere over Northwest Shandong was convective instability. The cold surface gradually thickened with the invasion of cold air, and there was conditional symmetric instability near the cold front over Northwest Shandong. The mesoscale vortex at 800 hPa triggered convection above the inversion layer and generated lightning. (4) It could be seen from the dualpolarization radar products that there were obvious twolayer echoes around the station when thunder snow occurred, and the concentration of ice phase particles at -10 ℃ layer height (about 600 hPa) was relatively large, which might be one of the lightning mechanism.
2023, 51(4):573-581.
DOI: 10.19517/j.1671-6345.20220307
Abstract:
On August 3, 2021, there was a strong thunderstorm and gale weather case with shortterm heavy rainfall and a downburst in Liuzhou. In this case, the cause of the downburst is analyzed by using observation data, minutelevel data from the Liuzhou automatic station, radar, wind profile and other data. The results show that: (1) This case was triggered by the rise of the surface mesoscale convergence line, under the background of the middle and lower layers of northeast airflow between the continental high and the tropical convergence zone, and favourable environmental conditions such as weak vertical wind shear, strong unstable energy, deep dry air source, and dry adiabatic decline near the ground. (2) The initial echo of the downburst had the characteristics of the pulse storm and then developed into the multi-cell storm. Before the downburst, the reflectivity core decreased, and the lower-level inflow and the middle-level radial convergence increased. Its vertical structure showed lower-level divergence, middle-level convergence, and middle-upper-level convergence rotation. (3) The wind profile radar wind field had obvious upper air momentum downward transmission and lower-level wind speed reduction before the ground gale appeared. The gale appeared at the time when the lower-level wind speed started to increase, earlier than the time when the lower-level wind speed was strongest. (4) The downburst was related to the drag and negative buoyancy of precipitation particles. The topography made the strong convection echo move along the topography, and the downhill topography and the isthmus effect had a superposition effect on the formation of extreme gales.
On August 3, 2021, there was a strong thunderstorm and gale weather case with shortterm heavy rainfall and a downburst in Liuzhou. In this case, the cause of the downburst is analyzed by using observation data, minutelevel data from the Liuzhou automatic station, radar, wind profile and other data. The results show that: (1) This case was triggered by the rise of the surface mesoscale convergence line, under the background of the middle and lower layers of northeast airflow between the continental high and the tropical convergence zone, and favourable environmental conditions such as weak vertical wind shear, strong unstable energy, deep dry air source, and dry adiabatic decline near the ground. (2) The initial echo of the downburst had the characteristics of the pulse storm and then developed into the multi-cell storm. Before the downburst, the reflectivity core decreased, and the lower-level inflow and the middle-level radial convergence increased. Its vertical structure showed lower-level divergence, middle-level convergence, and middle-upper-level convergence rotation. (3) The wind profile radar wind field had obvious upper air momentum downward transmission and lower-level wind speed reduction before the ground gale appeared. The gale appeared at the time when the lower-level wind speed started to increase, earlier than the time when the lower-level wind speed was strongest. (4) The downburst was related to the drag and negative buoyancy of precipitation particles. The topography made the strong convection echo move along the topography, and the downhill topography and the isthmus effect had a superposition effect on the formation of extreme gales.
2023, 51(4):582-594.
DOI: 10.19517/j.1671-6345.20220243
Abstract:
In this paper, the Extreme Forecast Index (EFI) related to short-time heavy precipitation, thunderstorm gale and hail in Zhejiang is calculated using ECWMF ensemble prediction data and Zhejiang automatic station observation data from 2016 to 2021. The characteristics of EFI are analyzed, and the forecast model is built. Results show that severe convective weather is closely related to the EFI of physical quantities. When short-time heavy precipitation occurs, the physical quantities with larger EFI are convective effective potential energy, whole layer precipitable water, temperature difference and potential temperature difference between 850 hPa and 500 hPa. While the EFI of vertical wind shear is negative, indicating that the smaller vertical wind shear is more conducive to the occurrence of extreme precipitation. When thunderstorms and hailstorms occur, the physical quantities with a larger EFI index are convective effective potential energy, temperature difference and potential temperature difference between 850 hPa and 500 hPa, and temperature dew point difference of 850 hPa. EFI of dew point temperature of 700 hPa is negative, related to the favourable stratification condition of the dry and cold upper layer with the warm and wet lower layer. By using the multi-classification method of the Support Vector Machine, the EFI of the physical quantities related to the strong convective weather are used as the characteristic value to carry out training. The prediction model is effective for nonlocal severe convective weather, and the misjudgment rate of short-term heavy precipitation is obviously lower than that of thunderstorm gale.
In this paper, the Extreme Forecast Index (EFI) related to short-time heavy precipitation, thunderstorm gale and hail in Zhejiang is calculated using ECWMF ensemble prediction data and Zhejiang automatic station observation data from 2016 to 2021. The characteristics of EFI are analyzed, and the forecast model is built. Results show that severe convective weather is closely related to the EFI of physical quantities. When short-time heavy precipitation occurs, the physical quantities with larger EFI are convective effective potential energy, whole layer precipitable water, temperature difference and potential temperature difference between 850 hPa and 500 hPa. While the EFI of vertical wind shear is negative, indicating that the smaller vertical wind shear is more conducive to the occurrence of extreme precipitation. When thunderstorms and hailstorms occur, the physical quantities with a larger EFI index are convective effective potential energy, temperature difference and potential temperature difference between 850 hPa and 500 hPa, and temperature dew point difference of 850 hPa. EFI of dew point temperature of 700 hPa is negative, related to the favourable stratification condition of the dry and cold upper layer with the warm and wet lower layer. By using the multi-classification method of the Support Vector Machine, the EFI of the physical quantities related to the strong convective weather are used as the characteristic value to carry out training. The prediction model is effective for nonlocal severe convective weather, and the misjudgment rate of short-term heavy precipitation is obviously lower than that of thunderstorm gale.
2023, 51(4):595-604.
DOI: 10.19517/j.1671-6345.20220141
Abstract:
Based on the rainfall data and hydrological data from May to September in the east part of the north slope of the Qilian Mountains, we analyze the effect of artificial rain enhancement from 2010 to 2020 by using four mathematical statistical test methods, including non-randomized experiments, using sequence, regional comparison, regional double ratio and regional regression. The results show that artificial rain enhancement tests in the east part of the north slope of the Qilian Mountains are positive effects, proved by the four methods of effect evaluation. The effectiveness tests of region contrast, region double ratio and region regression pass the test of significance level α≤0.10. Through the analysis of the four evaluation test methods, the regional historical regression test method uses a large sample size, avoiding the artificial selection of historically similar weather is prone to introduce numerous subjective biases and controversial operating procedures, resulting in the smallest false effect and the highest efficacy compared with other tests, which can be used as the final evaluation result. The average relative cloud-seeding effectiveness in the eastern northern slope of the Qilian Mountains from 2010 to 2020 is 26%. The impact of large-scale artificial rainfall on the ecological environment improvement of the Shiyang River basin in the eastern northern slope of the Qilian Mountains from 2010 to 2020 is further evaluated. The analysis finds that the annual average runoff of the Shiyang River increases by 124.6%, and the annual average discharge of the Caiqi section in Minqin increases by 124.3%. The groundwater level in Minqin Basin rises by 2.46 m, and the water area of Qingtuhu Lake, which has been dry for nearly half a century, continues to increase.
Based on the rainfall data and hydrological data from May to September in the east part of the north slope of the Qilian Mountains, we analyze the effect of artificial rain enhancement from 2010 to 2020 by using four mathematical statistical test methods, including non-randomized experiments, using sequence, regional comparison, regional double ratio and regional regression. The results show that artificial rain enhancement tests in the east part of the north slope of the Qilian Mountains are positive effects, proved by the four methods of effect evaluation. The effectiveness tests of region contrast, region double ratio and region regression pass the test of significance level α≤0.10. Through the analysis of the four evaluation test methods, the regional historical regression test method uses a large sample size, avoiding the artificial selection of historically similar weather is prone to introduce numerous subjective biases and controversial operating procedures, resulting in the smallest false effect and the highest efficacy compared with other tests, which can be used as the final evaluation result. The average relative cloud-seeding effectiveness in the eastern northern slope of the Qilian Mountains from 2010 to 2020 is 26%. The impact of large-scale artificial rainfall on the ecological environment improvement of the Shiyang River basin in the eastern northern slope of the Qilian Mountains from 2010 to 2020 is further evaluated. The analysis finds that the annual average runoff of the Shiyang River increases by 124.6%, and the annual average discharge of the Caiqi section in Minqin increases by 124.3%. The groundwater level in Minqin Basin rises by 2.46 m, and the water area of Qingtuhu Lake, which has been dry for nearly half a century, continues to increase.
2023, 51(4):605-612.
DOI: 10.19517/j.1671-6345.20220266
Abstract:
To design and improve the weather index insurance product for frost injury in apple florescence, Xunyi is selected as the representative apple planting county in the Weibei region of Shaanxi Province. The data of meteorology, apple flowering phenophase and yields from 1991 to 2020 are used for design and analysis. The meteorological yield of apples is separated by using moving average and grey prediction methods. The weather index based on extremely low temperatures and the frost injury process cumulative hazard during apple flowering is constructed for selection. The weather index for frost injury in apple florescence is determined by correlation analysis between weather index and yield reduction rate. The regression model between weather index and yield reduction rate is constructed. According to apple yield risk distribution characteristics, using the parameter distribution method, a variety of distribution models are selected to fit apple yield risk distribution. The optimal distribution model is selected by A-D test results and probability density function diagram. The pure premium rates are determined under different compensation trigger conditions. Results show that the correlation between cumulative hazard weather index in the frost injury process and yield reduction rate is higher than that between extremely lowtemperature weather index in representative counties and yield reduction rate. The yield reduction rate has a linear relationship with the ∑Ts weather index. Apple yield risk distribution fit to Cauchy distribution. The pure premium rates of weather index insurance products for frost injury in apple florescence are from 0.40 to 1.84 percent when yield reduction rates are 2,4,6 and 8 percent in Xunyi. The rationality and applicability of the weather index insurance product have been enhanced compared to traditional agricultural insurance products, which is beneficial to giving full advantages to weather index insurance.
To design and improve the weather index insurance product for frost injury in apple florescence, Xunyi is selected as the representative apple planting county in the Weibei region of Shaanxi Province. The data of meteorology, apple flowering phenophase and yields from 1991 to 2020 are used for design and analysis. The meteorological yield of apples is separated by using moving average and grey prediction methods. The weather index based on extremely low temperatures and the frost injury process cumulative hazard during apple flowering is constructed for selection. The weather index for frost injury in apple florescence is determined by correlation analysis between weather index and yield reduction rate. The regression model between weather index and yield reduction rate is constructed. According to apple yield risk distribution characteristics, using the parameter distribution method, a variety of distribution models are selected to fit apple yield risk distribution. The optimal distribution model is selected by A-D test results and probability density function diagram. The pure premium rates are determined under different compensation trigger conditions. Results show that the correlation between cumulative hazard weather index in the frost injury process and yield reduction rate is higher than that between extremely lowtemperature weather index in representative counties and yield reduction rate. The yield reduction rate has a linear relationship with the ∑Ts weather index. Apple yield risk distribution fit to Cauchy distribution. The pure premium rates of weather index insurance products for frost injury in apple florescence are from 0.40 to 1.84 percent when yield reduction rates are 2,4,6 and 8 percent in Xunyi. The rationality and applicability of the weather index insurance product have been enhanced compared to traditional agricultural insurance products, which is beneficial to giving full advantages to weather index insurance.
External LinksChina Meteorological AdministrationCMA Meteorological Observation CentreChinese Academy of Meteorological SciencesBeijing Meteorological ServiceNational Satellite Meteorological Center
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.