ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 47,Issue 6,2021 Table of Contents
2021, 47(6):645-654.
DOI: 10.7519/j.issn.1000-0526.2021.06.001
Abstract:
Developments of operational global mediumrange forecast system of National Meteorological Centre are reviewed. The topics focus on the advances in science and technology in National Meteorological Centre since the setup of global forecast system. The improvements in localization, operational application and further development of sequence of spectral model series are summarized, and those in progress of selfdeveloped global medium range forecast system, GRAPES_GFS, are described in detail.
Developments of operational global mediumrange forecast system of National Meteorological Centre are reviewed. The topics focus on the advances in science and technology in National Meteorological Centre since the setup of global forecast system. The improvements in localization, operational application and further development of sequence of spectral model series are summarized, and those in progress of selfdeveloped global medium range forecast system, GRAPES_GFS, are described in detail.
CHEN Yun
,
CAO Yong
,
SUN Jian
,
FU Jiaolan
,
DONG Quan
,
YU Chao
,
LIU Couhua
,
TANG Jian
,
GUO Yunqian
2021, 47(6):655-670.
DOI: 10.7519/j.issn.1000-0526.2021.06.002
Abstract:
Quantitative precipitation forecast (QPF) is the traditional and critical forecasting operation of National Meteorological Centre (NMC). With the rapid development of society and economy and its increasing demand in the fineness of various meteorological products, developing the fine gridded QPF has become the primary task of NMC. A fine gridded QPF product system with a spatial resolution of 5 km and 1 h 〖JP2〗interval for 3 d lead time and 3 h interval for 3-10 d lead time has been built, which covers rain, sleet, freezing rain, snow and depth of new snowfall forecast. This paper presents the progress of the related technology development in high resolution numerical weather forecast model, fine gridded QPF, gridded precipitation type and depth of new snowfall forecast and refined QPF verification. Finally, the existing problems and future developments of the current fine gridded QPF technology are discussed.
Quantitative precipitation forecast (QPF) is the traditional and critical forecasting operation of National Meteorological Centre (NMC). With the rapid development of society and economy and its increasing demand in the fineness of various meteorological products, developing the fine gridded QPF has become the primary task of NMC. A fine gridded QPF product system with a spatial resolution of 5 km and 1 h 〖JP2〗interval for 3 d lead time and 3 h interval for 3-10 d lead time has been built, which covers rain, sleet, freezing rain, snow and depth of new snowfall forecast. This paper presents the progress of the related technology development in high resolution numerical weather forecast model, fine gridded QPF, gridded precipitation type and depth of new snowfall forecast and refined QPF verification. Finally, the existing problems and future developments of the current fine gridded QPF technology are discussed.
3 Progress and Challenge of National Level Operational Technology for Hydrometeorological Forecasting
BAO Hongjun
,
ZHANG Hengde
,
XU Fengwen
,
DI Jingyue
,
WANG Meng
,
CAO Shuang
,
YANG Yin
,
LI Yumei
,
LIU Haizhi
2021, 47(6):671-684.
DOI: 10.7519/j.issn.1000-0526.2021.06.003
Abstract:
The forecasting operation of quantitative hydrometeorology with accurate spatiotemporal distribution is to meet the demands of the national disaster prevention and mitigation, major projects support, expanding impacted forecasting and risk warning. Although great progresses in the hydrometeorological forecasting have been made in National Meteorological Centre in the recent years, there are still many gaps compared with the advanced forecasting technology in foreign countries. The current development of technique and operation status of the hydrometeorological forecasting was reviewed in this paper. In addition, the current challenges facing China were summarized and the corresponding measures and further development plans were proposed. At present, the main techniques on hydrometeorological forecasting can be classified as two types: the rainfall threshold model based on statistical theory and the distributed hydrological model. Moreover, the atmospherichydrologicalgeological model based on big data analysis and artificial intelligence technique will play important roles in the hydrometeorological forecasting. Hydrometeorological monitoring with satellite, radar and gauge observations is the foundation of hydrometeorological forecasting. Hydrometeorological forecasting based on seamless fine intelligentandgrid QPF and hydrometeorological ensemble forecasting model will be the important development directions of the hydrological forecasting in the future.
The forecasting operation of quantitative hydrometeorology with accurate spatiotemporal distribution is to meet the demands of the national disaster prevention and mitigation, major projects support, expanding impacted forecasting and risk warning. Although great progresses in the hydrometeorological forecasting have been made in National Meteorological Centre in the recent years, there are still many gaps compared with the advanced forecasting technology in foreign countries. The current development of technique and operation status of the hydrometeorological forecasting was reviewed in this paper. In addition, the current challenges facing China were summarized and the corresponding measures and further development plans were proposed. At present, the main techniques on hydrometeorological forecasting can be classified as two types: the rainfall threshold model based on statistical theory and the distributed hydrological model. Moreover, the atmospherichydrologicalgeological model based on big data analysis and artificial intelligence technique will play important roles in the hydrometeorological forecasting. Hydrometeorological monitoring with satellite, radar and gauge observations is the foundation of hydrometeorological forecasting. Hydrometeorological forecasting based on seamless fine intelligentandgrid QPF and hydrometeorological ensemble forecasting model will be the important development directions of the hydrological forecasting in the future.
2021, 47(6):685-692.
DOI: 10.7519/j.issn.1000-0526.2021.06.004
Abstract:
This article reviews the threedecade development of the typhoon numerical forecast operational system in the National Meteorological Centre (NMC) of China Meteorological Administration since the beginning of the Eighth FiveYear Plan, including its firstgeneration typhoon track numerical prediction system using regional model, a typhoon track numerical prediction system developed on the basis of the global spectral model, and the global and regional tropical cyclone (TC) forecast system independently developed by the China Meteorological Administration. It summarizes the key technologies and forecast performance of these systems, with a focus on the main technical achievements of GRAPES_TYM. It also puts forward some views on the development of the national typhoon numerical prediction system in the next five years.
This article reviews the threedecade development of the typhoon numerical forecast operational system in the National Meteorological Centre (NMC) of China Meteorological Administration since the beginning of the Eighth FiveYear Plan, including its firstgeneration typhoon track numerical prediction system using regional model, a typhoon track numerical prediction system developed on the basis of the global spectral model, and the global and regional tropical cyclone (TC) forecast system independently developed by the China Meteorological Administration. It summarizes the key technologies and forecast performance of these systems, with a focus on the main technical achievements of GRAPES_TYM. It also puts forward some views on the development of the national typhoon numerical prediction system in the next five years.
2021, 47(6):693-702.
DOI: 10.7519/j.issn.1000-0526.2021.06.005
Abstract:
In recent 10 years, the refinement level and dynamic, quantitative capacity of agrometeorological disaster forecasting and assessment have been promoted accompanied with the development of the agrometeorological disaster monitoring and assessment theory, the comprehensive use of numerical simulation technology, remote sensing monitoring technology, and modern information technology, as well as the application of intelligent grid meteorological element prediction in agrometeorological disaster monitoring and forecasting operation. All these have played an important role in agricultural disaster prevention and reduction and in yield improvement. In this paper, the main research and service achievements of dynamic, quantitative and refined agrometeorological disaster forecasting and assessment in recent 10 years are introduced, and the future development trend is looked forward to so as to provide a reference for the further development of agrometeorological disaster forecasting and assessment services.
In recent 10 years, the refinement level and dynamic, quantitative capacity of agrometeorological disaster forecasting and assessment have been promoted accompanied with the development of the agrometeorological disaster monitoring and assessment theory, the comprehensive use of numerical simulation technology, remote sensing monitoring technology, and modern information technology, as well as the application of intelligent grid meteorological element prediction in agrometeorological disaster monitoring and forecasting operation. All these have played an important role in agricultural disaster prevention and reduction and in yield improvement. In this paper, the main research and service achievements of dynamic, quantitative and refined agrometeorological disaster forecasting and assessment in recent 10 years are introduced, and the future development trend is looked forward to so as to provide a reference for the further development of agrometeorological disaster forecasting and assessment services.
2021, 47(6):703-716.
DOI: 10.7519/j.issn.1000-0526.2021.06.006
Abstract:
An X-band dual-polarization phased array radar (XPAR) network is being set up in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) to improve observation accuracy and enhance low-altitude observation capability. In order to solve the raindrop attenuation problem of X-band radar and meet the requirements of observation and networking, self-consistent algorithm for attenuation correction is introduced and localized. The results show that the correction amplitude of reflectivity factor reaches 6 dB, and the negative 〖JP2〗value of differential reflectivity is also effectively constrained. Scatter analysis and quantitative statistical results of adjacent XPARs show that the spatial and intensity distributions of the two groups of data after quality control have a high consistency. Compared with S-band radar data which are taken as the truth value, the XPAR intensity of reflectivity factor is weak before attenuation correction, but enhanced to the equivalent strength of the S-band radar after correction, which is stronger locally and the accuracy is significantly improved. Differential reflectivity is corrected to some extent, the scatter distribution of corrected differential reflectivity and reflectivity factor is more concentrated and related coefficient is higher. It can be seen that this algorithm solves well the rain area attenuation problem of X-band phased array radar, and provides early data quality assurance for the promotion and application of X-band phased array radar network data and product development in the GBA.
An X-band dual-polarization phased array radar (XPAR) network is being set up in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) to improve observation accuracy and enhance low-altitude observation capability. In order to solve the raindrop attenuation problem of X-band radar and meet the requirements of observation and networking, self-consistent algorithm for attenuation correction is introduced and localized. The results show that the correction amplitude of reflectivity factor reaches 6 dB, and the negative 〖JP2〗value of differential reflectivity is also effectively constrained. Scatter analysis and quantitative statistical results of adjacent XPARs show that the spatial and intensity distributions of the two groups of data after quality control have a high consistency. Compared with S-band radar data which are taken as the truth value, the XPAR intensity of reflectivity factor is weak before attenuation correction, but enhanced to the equivalent strength of the S-band radar after correction, which is stronger locally and the accuracy is significantly improved. Differential reflectivity is corrected to some extent, the scatter distribution of corrected differential reflectivity and reflectivity factor is more concentrated and related coefficient is higher. It can be seen that this algorithm solves well the rain area attenuation problem of X-band phased array radar, and provides early data quality assurance for the promotion and application of X-band phased array radar network data and product development in the GBA.
2021, 47(6):717-726.
DOI: 10.7519/j.issn.1000-0526.2021.06.007
Abstract:
By using the daily data from 50 stations and ERA-Interim reanalysis data in Qinghai Plateau during 1980-2018, and the methods of linear regression, Pearson correlation analysis and probability density distribution, this paper analyzed the spatio-temporal characteristics of hail frequency, hail diameter, hail duration, and the effects of elevations, special layer heights, and surface temperature on hail. The results demonstrate that the mean hail frequency in Qinghai Plateau has decreased significantly in the recent 39 years, especially since 2000. Hail events are most seen in June and July, with a fast decline rate in a year. The mean single time hail duration has decreased significantly, while the occurrence of large hail events has increased since the middle-late of 1990s. From the spatial distribution, the high value areas of hail frequency and duration are in the south part of Qinghai Plateau with high elevation, while the high value areas of mean hail diameter are in the eastern part of Qinghai Plateau with lower altitudes. The hail diameter in 3-5 mm〖JP〗 and duration 2-3 min of hail events have the highest frequeney. The lower 0℃ and -20℃ isotherm heights are favorable for hail formation and prolonging the hail duration. The higher 0℃ and -20℃ isotherm heights play an important role in supporting the collision and growth of hail in the air. The decreases of hail frequency and hail duration are related to the significant increase in mean surface air temperature and decrease in diurnal temperature range as well as the rising of 0℃ and -20℃ layer heights.
By using the daily data from 50 stations and ERA-Interim reanalysis data in Qinghai Plateau during 1980-2018, and the methods of linear regression, Pearson correlation analysis and probability density distribution, this paper analyzed the spatio-temporal characteristics of hail frequency, hail diameter, hail duration, and the effects of elevations, special layer heights, and surface temperature on hail. The results demonstrate that the mean hail frequency in Qinghai Plateau has decreased significantly in the recent 39 years, especially since 2000. Hail events are most seen in June and July, with a fast decline rate in a year. The mean single time hail duration has decreased significantly, while the occurrence of large hail events has increased since the middle-late of 1990s. From the spatial distribution, the high value areas of hail frequency and duration are in the south part of Qinghai Plateau with high elevation, while the high value areas of mean hail diameter are in the eastern part of Qinghai Plateau with lower altitudes. The hail diameter in 3-5 mm〖JP〗 and duration 2-3 min of hail events have the highest frequeney. The lower 0℃ and -20℃ isotherm heights are favorable for hail formation and prolonging the hail duration. The higher 0℃ and -20℃ isotherm heights play an important role in supporting the collision and growth of hail in the air. The decreases of hail frequency and hail duration are related to the significant increase in mean surface air temperature and decrease in diurnal temperature range as well as the rising of 0℃ and -20℃ layer heights.
2021, 47(6):727-736.
DOI: 10.7519/j.issn.1000-0526.2021.06.008
Abstract:
A list control method is proposed, which considers the acquisition rate, acquisition punctuality rate, quality control accuracy rate and model consistency rate of observation data. The wind observation data of 120 radiosonde stations in 2019 are used to validate the method, and analyze the quality of observation data. The results are as follows. The stations with observation data problems can be effectively checked out by the list control method. Compared with the model data, the observation data of the list stations have obvious systematic deviation, and the bias and root mean square error (RMSE) are significantly larger than the national averages. The quality of radiosonde wind observation data is good, and the wind direction and wind speed observation data are relatively consistent with the model data in all the four seasons with the biases are within ±1° and ±1.5 m·s-1, respectively. The wind direction consistency in autumn is the highest, and the wind speed consistency in summer and winter is lower than that in spring and autumn. The wind direction consistency first decreases and then increases with the decrease of pressure in spring and summer, while it is opposite in autumn and winter. The wind speed consistency basically changes in a threepeak pattern with the decrease of pressure.
A list control method is proposed, which considers the acquisition rate, acquisition punctuality rate, quality control accuracy rate and model consistency rate of observation data. The wind observation data of 120 radiosonde stations in 2019 are used to validate the method, and analyze the quality of observation data. The results are as follows. The stations with observation data problems can be effectively checked out by the list control method. Compared with the model data, the observation data of the list stations have obvious systematic deviation, and the bias and root mean square error (RMSE) are significantly larger than the national averages. The quality of radiosonde wind observation data is good, and the wind direction and wind speed observation data are relatively consistent with the model data in all the four seasons with the biases are within ±1° and ±1.5 m·s-1, respectively. The wind direction consistency in autumn is the highest, and the wind speed consistency in summer and winter is lower than that in spring and autumn. The wind direction consistency first decreases and then increases with the decrease of pressure in spring and summer, while it is opposite in autumn and winter. The wind speed consistency basically changes in a threepeak pattern with the decrease of pressure.
2021, 47(6):737-745.
DOI: 10.7519/j.issn.1000-0526.2021.06.009
Abstract:
From 20:00 BT 9 to 20:00 BT 13 August 2020, due to the combined effects of the westerly trough and the Typhoon Lichma, largescale severe precipitation occurred in Shandong Province. The center of the severe precipitation was at Zhangqiu Station. In order to use multisource data to study the microphysical structure characteristics of heavy rainfalls in the typhoon rain belt, this paper analyzes the data of minutely precipitation, raindrop spectrum, dual polarization Doppler radar, wind profiler radar, etc. during the severe rainfall process at Zhangqiu Station. The results show that there was an obvious cold cloud precipitation mechanism at the beginning of this precipitation process. During the precipitation, the scale spectrum of raindrops changed significantly with time. During the period of severe precipitation, the spectrum of raindrops was broad, showing an obvious bimodal structure. The correlation coefficient between the sequence of raindrop numbers with a diameter greater than 1 mm and the sequence of minutely precipitation reached 0.956 〖KG-*5〗8. However, during periods of weakening precipitation, the spectrum of raindrops gradually narrowed, showing a singlepeak structure clearly, and the number of raindrops with a diameter greater than 1 mm decreased. When the radar echo height was high, the proportion of raindrops with a diameter greater than 1 mm increased, the raindrop spectrum was wider, and the multimodal distribution appeared. Strong wet turbulence clusters formed a large value area of the differential reflectance factor (ZDR), which neither corresponded to severe convection nor to surface heavy raindrops. This was caused jointly by the deformation of the wet turbulence resulting from updraft, downdraft and other reasons. During heavier precipitation, a thin layer structure with abrupt changes in wind direction and wind speed appeared in the time crosssection of wind profile in the 0.9-1.4 km height. Corresponding to the thin layer, the minutely rainfall was the heaviest, and the proportion of raindrops with a diameter greater than 1 mm was obviously biased. The phenomenon revealed by the analysis results could provide a reference for understanding the droplet spectrum characteristics and microphysical structure of typhoon heavy rainfall.
From 20:00 BT 9 to 20:00 BT 13 August 2020, due to the combined effects of the westerly trough and the Typhoon Lichma, largescale severe precipitation occurred in Shandong Province. The center of the severe precipitation was at Zhangqiu Station. In order to use multisource data to study the microphysical structure characteristics of heavy rainfalls in the typhoon rain belt, this paper analyzes the data of minutely precipitation, raindrop spectrum, dual polarization Doppler radar, wind profiler radar, etc. during the severe rainfall process at Zhangqiu Station. The results show that there was an obvious cold cloud precipitation mechanism at the beginning of this precipitation process. During the precipitation, the scale spectrum of raindrops changed significantly with time. During the period of severe precipitation, the spectrum of raindrops was broad, showing an obvious bimodal structure. The correlation coefficient between the sequence of raindrop numbers with a diameter greater than 1 mm and the sequence of minutely precipitation reached 0.956 〖KG-*5〗8. However, during periods of weakening precipitation, the spectrum of raindrops gradually narrowed, showing a singlepeak structure clearly, and the number of raindrops with a diameter greater than 1 mm decreased. When the radar echo height was high, the proportion of raindrops with a diameter greater than 1 mm increased, the raindrop spectrum was wider, and the multimodal distribution appeared. Strong wet turbulence clusters formed a large value area of the differential reflectance factor (ZDR), which neither corresponded to severe convection nor to surface heavy raindrops. This was caused jointly by the deformation of the wet turbulence resulting from updraft, downdraft and other reasons. During heavier precipitation, a thin layer structure with abrupt changes in wind direction and wind speed appeared in the time crosssection of wind profile in the 0.9-1.4 km height. Corresponding to the thin layer, the minutely rainfall was the heaviest, and the proportion of raindrops with a diameter greater than 1 mm was obviously biased. The phenomenon revealed by the analysis results could provide a reference for understanding the droplet spectrum characteristics and microphysical structure of typhoon heavy rainfall.
2021, 47(6):746-754.
DOI: 10.7519/j.issn.1000-0526.2021.06.010
Abstract:
Based on the hourly 2 m temperature, relative humidity, surface pressure and visibility data of 158 stations in Sichuan Province during the period 1967-2008, the monthly sunny global horizontal irradiation (GHI) was calculated and integrated by using simple model for atmospheric transmission of sunshine (SMARTS). The relationship between sunny GHI and altitude was established, which was applied to the correction of GHI interpolation during the period 1990-2019, and the correction effect was verified. The results show that the sunny GHI increases logarithmically with altitude, and the higher the altitude is, the smaller the increase of sunny GHI with altitude becomes. In terms of radiation correction, the correction range of Sichuan Basin with low altitude and flat terrain is the smallest, the high-altitude plateau in western Sichuan is in the middle, the transition zone between high and low altitudes is the largest. The results of cross validation show that the annual mean absolute error of the seven stations is reduced from 182.77 kW·h·m-2 to 145.48 kW·h·m-2, while the relative error is reduced from 13.41% to 10.24%.
Based on the hourly 2 m temperature, relative humidity, surface pressure and visibility data of 158 stations in Sichuan Province during the period 1967-2008, the monthly sunny global horizontal irradiation (GHI) was calculated and integrated by using simple model for atmospheric transmission of sunshine (SMARTS). The relationship between sunny GHI and altitude was established, which was applied to the correction of GHI interpolation during the period 1990-2019, and the correction effect was verified. The results show that the sunny GHI increases logarithmically with altitude, and the higher the altitude is, the smaller the increase of sunny GHI with altitude becomes. In terms of radiation correction, the correction range of Sichuan Basin with low altitude and flat terrain is the smallest, the high-altitude plateau in western Sichuan is in the middle, the transition zone between high and low altitudes is the largest. The results of cross validation show that the annual mean absolute error of the seven stations is reduced from 182.77 kW·h·m-2 to 145.48 kW·h·m-2, while the relative error is reduced from 13.41% to 10.24%.
LI Xiufen
,
JIANG Lixia
,
LI Xianfeng
,
ZHAO Fang
,
ZHU Haixia
,
WANG Ping
,
GONG Lijuan
,
ZHAO Huiying
2021, 47(6):755-766.
DOI: 10.7519/j.issn.1000-0526.2021.06.011
Abstract:
In this study, instrumentmeasured evaporation and conventional meteorological observations from 80 stations in Heilongjiang Province from 1961 to 2017 were collected. Using these data, methods such as linear trend estimation, cumulative anomaly, MannKendal mutation analysis, mathematical statistics and Marr’s wavelet analysis were employed to analyze the annual and seasonal characteristics of the spatiotemporal evolution of instrumentmeasured evaporation in Heilongjiang Province. Additionally, the relationships of the characteristics with climate factors were analyzed. The results show that the geographical correlation of annual evaporation is significant. Annual evaporation decreases as latitude, longitude and altitude increased. The decreasing rates are 55.4 mm/°N, 45.2 mm/°E and 88.8 mm/(100 m), respectively. From 1961 to 2017, annual evaporation in Heilongjiang Province showed a significant downward trend, decreasing at 13.7 mm/(10 a). Annual evaporation had 8 a and 24 a cycles. Statistics show that at up to 70.0% of the stations, the annual pan evaporation show a downward trend, of which 62.5% of the stations have passed the significance test at 0.05 level, which means there is “evaporation paradox” in Heilongjiang Province. Exploring seasonal pan evaporation trend shows that evaporation decreased significantly in spring, having 24 a and quasi2 a cycles, and 67 stations show a downward trend, 44 of which show a significant downward trend (P<0.05). However, the magnitude of this decrease in summer and fall is relatively small with nonsignificant changes, with 7 a cycles. In winter, evaporation increase slightly having 24 a, 11 a, and 2 a cycles and 23 stations show a significant rising trend. Mutation test shows that there is a significant mutation time of evaporation in year, spring and winter, but no significant mutation in summer and autumn. Additionally, it is found that changes in annual and seasonal pan evaporation are positively correlated with average temperature and wind speed, and negatively correlated with humidity. Our analysis indicates that a significant decrease in wind speed is the dominant factor leading to the decrease in evaporation throughout the year, and the superposition effect of a significant decrease in wind speed and obvious humidification makes the decrease trend of spring evaporation more significant. The higher temperature and lower relative humidity climate may be the cause of the slight increase in evaporation in winter.
In this study, instrumentmeasured evaporation and conventional meteorological observations from 80 stations in Heilongjiang Province from 1961 to 2017 were collected. Using these data, methods such as linear trend estimation, cumulative anomaly, MannKendal mutation analysis, mathematical statistics and Marr’s wavelet analysis were employed to analyze the annual and seasonal characteristics of the spatiotemporal evolution of instrumentmeasured evaporation in Heilongjiang Province. Additionally, the relationships of the characteristics with climate factors were analyzed. The results show that the geographical correlation of annual evaporation is significant. Annual evaporation decreases as latitude, longitude and altitude increased. The decreasing rates are 55.4 mm/°N, 45.2 mm/°E and 88.8 mm/(100 m), respectively. From 1961 to 2017, annual evaporation in Heilongjiang Province showed a significant downward trend, decreasing at 13.7 mm/(10 a). Annual evaporation had 8 a and 24 a cycles. Statistics show that at up to 70.0% of the stations, the annual pan evaporation show a downward trend, of which 62.5% of the stations have passed the significance test at 0.05 level, which means there is “evaporation paradox” in Heilongjiang Province. Exploring seasonal pan evaporation trend shows that evaporation decreased significantly in spring, having 24 a and quasi2 a cycles, and 67 stations show a downward trend, 44 of which show a significant downward trend (P<0.05). However, the magnitude of this decrease in summer and fall is relatively small with nonsignificant changes, with 7 a cycles. In winter, evaporation increase slightly having 24 a, 11 a, and 2 a cycles and 23 stations show a significant rising trend. Mutation test shows that there is a significant mutation time of evaporation in year, spring and winter, but no significant mutation in summer and autumn. Additionally, it is found that changes in annual and seasonal pan evaporation are positively correlated with average temperature and wind speed, and negatively correlated with humidity. Our analysis indicates that a significant decrease in wind speed is the dominant factor leading to the decrease in evaporation throughout the year, and the superposition effect of a significant decrease in wind speed and obvious humidification makes the decrease trend of spring evaporation more significant. The higher temperature and lower relative humidity climate may be the cause of the slight increase in evaporation in winter.
2021, 47(6):767-772.
DOI: 10.7519/j.issn.1000-0526.2021.06.012
Abstract:
The main characteristics of the general atmospheric circulation in March 2021 are as follows. There were two polar vortex centers in the Northern Hemisphere, the 500 hPa geopotential height presented the distribution of a threewave pattern in the midhigh latitude of Northern Hemisphere. The strength of Western Pacific subtropical high was closed to that in normal years, and the south branch though was a little weaker. The national average temperature in March was 6.6℃, 2.5℃ higher than the normal (4.1℃) and recorded the second highest in the same period since 1961. The monthly mean precipitation amount was 27.8 mm, 6% less than in normal period (29.5 mm). There were three largescale sanddust weather processes in March, which were more and stronger than the usual, of which the sanddust weather in 13-18 was the strongest sanddust weather process in the past 10 years. A severe convective weather process occurred in the Yangtze River Basin at the end of the month, causing severe weather such as hail and thunderstorm. During this month, cold airs were weak, and only one moderate cold wave process appeared in 15-17. The droughts continued in Yunnan Province, droughts appeared and developed in South China.
The main characteristics of the general atmospheric circulation in March 2021 are as follows. There were two polar vortex centers in the Northern Hemisphere, the 500 hPa geopotential height presented the distribution of a threewave pattern in the midhigh latitude of Northern Hemisphere. The strength of Western Pacific subtropical high was closed to that in normal years, and the south branch though was a little weaker. The national average temperature in March was 6.6℃, 2.5℃ higher than the normal (4.1℃) and recorded the second highest in the same period since 1961. The monthly mean precipitation amount was 27.8 mm, 6% less than in normal period (29.5 mm). There were three largescale sanddust weather processes in March, which were more and stronger than the usual, of which the sanddust weather in 13-18 was the strongest sanddust weather process in the past 10 years. A severe convective weather process occurred in the Yangtze River Basin at the end of the month, causing severe weather such as hail and thunderstorm. During this month, cold airs were weak, and only one moderate cold wave process appeared in 15-17. The droughts continued in Yunnan Province, droughts appeared and developed in South China.
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ISSN:1000-0526 CN:11-2282/P