ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 49,Issue 8,2023 Table of Contents
2023, 49(8):901-914.
DOI: 10.7519/j.issn.1000-0526.2023.021001
Abstract:
Due to the small spatiotemporal scale and large change rate of turbulence, and the lack of large-scale field observation, there are fewer researches on the characteristics of atmospheric turbulence in China. Since 2011, China has begun to store second-level high-resolution sounding data, which makes it possible to deeply study the characteristics of turbulence in various parts of China. When using radiosonde data to diagnose the characteristics of turbulence, it is necessary to consider the impact of instrument noise on the analysis results. This paper analyzes the impact of instrument noise on the analysis results in China, which proves that noise can reduce the average turbulent dissipation rate in the troposphere, indicating the necessity of removing noise. On this basis, the Thorpe analysis method is used in analyzing the relationship between the intensity of turbulence (turbulence dissipation rate) and the type of underlying surface in detail. The results reveal that the turbulence in the troposphere and the annual average grassland turbulence are the strongest, followed by those of dryland crops, paddy crops, shrubs and wasteland. In the lower stratosphere, it is still affected by the underlying surface, and the annual average turbulence of grassland is still the strongest, and the next is the turbulence of dry land crops. The turbulence shows obvious seasonality on different underlying surfaces, and the turbulence intensity and frequency in the upper troposphere are the highest in summer. The results of this paper would help to understand the turbulence characteristics of different underlying surfaces, and provide guidance for the improvement of turbulence parameterization schemes of aircraft flight safety guarantee, air pollution model and so on.
Due to the small spatiotemporal scale and large change rate of turbulence, and the lack of large-scale field observation, there are fewer researches on the characteristics of atmospheric turbulence in China. Since 2011, China has begun to store second-level high-resolution sounding data, which makes it possible to deeply study the characteristics of turbulence in various parts of China. When using radiosonde data to diagnose the characteristics of turbulence, it is necessary to consider the impact of instrument noise on the analysis results. This paper analyzes the impact of instrument noise on the analysis results in China, which proves that noise can reduce the average turbulent dissipation rate in the troposphere, indicating the necessity of removing noise. On this basis, the Thorpe analysis method is used in analyzing the relationship between the intensity of turbulence (turbulence dissipation rate) and the type of underlying surface in detail. The results reveal that the turbulence in the troposphere and the annual average grassland turbulence are the strongest, followed by those of dryland crops, paddy crops, shrubs and wasteland. In the lower stratosphere, it is still affected by the underlying surface, and the annual average turbulence of grassland is still the strongest, and the next is the turbulence of dry land crops. The turbulence shows obvious seasonality on different underlying surfaces, and the turbulence intensity and frequency in the upper troposphere are the highest in summer. The results of this paper would help to understand the turbulence characteristics of different underlying surfaces, and provide guidance for the improvement of turbulence parameterization schemes of aircraft flight safety guarantee, air pollution model and so on.
2023, 49(8):915-931.
DOI: 10.7519/j.issn.1000-0526.2023.060401
Abstract:
The hourly and half-hourly data assimilation sensitivity experiments for one regional persistent rainstorm process in southern Shandong from August 13 to 14 2020 are carried out using the half-hourly update and prediction system based on WRF with the purpose of exploring the application of high frequency data assimilation. The half-hourly data assimilation experiments include three assimilation schemes: assimilating of the automatic weather station (AWS) data and the aircraft meteorological data relay (AMDAR) data at the half-hour frequency, and “rejecting” one of them respectively. The results show that the half-hourly cooperative assimilation experiment of AWS observation and AMDAR data can significantly improve the numerical prediction of 24 h accumulated precipitation and 1 h short-term severe precipitation during this persistent rainstorm relative to the hourly assimilation experiment. This indicates that increasing the assimilation frequency to increase the utilization of high-frequency data has a positive effect on the numerical prediction. In the process of half-hourly data assimilation, the experiment of assimilating AWS data and AMDAR data at the same time is more accurate than the experiment of “rejecting” one of them respectively. The result of assimilation experiment “rejecting” AMDAR data is worse than that of “rejecting” AWS data, indicating that the assimilation of AMDAR data plays a more import role than that of AWS data in half-hourly assimilation. The improvement of initial field by rapid updating cyclic assimilation is a process of gradual adjustment. The experiments with different assimilation data and frequencies have different effects on the analysis field. The initial field of half-hourly assimilation experiment of collaborative assimilating AWS data and AMDAR data is the closest to the observation. The different positions of the high temperature and high humidity area of the ground element field relative to the convergence line under different assimilation schemes, and the different strength and configuration of high-altitude cold and warm air lead to different movement directions of the squall line system, which is the main reason for the great difference of precipitation areas in each experiment. However, the location difference of squall line system leads to the different degree of integration with the newborn system in the warm and humid airflow in the southwest, resulting in the difference of precipitation intensity in the future.
The hourly and half-hourly data assimilation sensitivity experiments for one regional persistent rainstorm process in southern Shandong from August 13 to 14 2020 are carried out using the half-hourly update and prediction system based on WRF with the purpose of exploring the application of high frequency data assimilation. The half-hourly data assimilation experiments include three assimilation schemes: assimilating of the automatic weather station (AWS) data and the aircraft meteorological data relay (AMDAR) data at the half-hour frequency, and “rejecting” one of them respectively. The results show that the half-hourly cooperative assimilation experiment of AWS observation and AMDAR data can significantly improve the numerical prediction of 24 h accumulated precipitation and 1 h short-term severe precipitation during this persistent rainstorm relative to the hourly assimilation experiment. This indicates that increasing the assimilation frequency to increase the utilization of high-frequency data has a positive effect on the numerical prediction. In the process of half-hourly data assimilation, the experiment of assimilating AWS data and AMDAR data at the same time is more accurate than the experiment of “rejecting” one of them respectively. The result of assimilation experiment “rejecting” AMDAR data is worse than that of “rejecting” AWS data, indicating that the assimilation of AMDAR data plays a more import role than that of AWS data in half-hourly assimilation. The improvement of initial field by rapid updating cyclic assimilation is a process of gradual adjustment. The experiments with different assimilation data and frequencies have different effects on the analysis field. The initial field of half-hourly assimilation experiment of collaborative assimilating AWS data and AMDAR data is the closest to the observation. The different positions of the high temperature and high humidity area of the ground element field relative to the convergence line under different assimilation schemes, and the different strength and configuration of high-altitude cold and warm air lead to different movement directions of the squall line system, which is the main reason for the great difference of precipitation areas in each experiment. However, the location difference of squall line system leads to the different degree of integration with the newborn system in the warm and humid airflow in the southwest, resulting in the difference of precipitation intensity in the future.
2023, 49(8):932-945.
DOI: 10.7519/j.issn.1000-0526.2023.061201
Abstract:
On 26 July 2018 (shortly for “7·26”) and 29 July 2018 (shortly for “7·29”), the gust front formed by the cold outflow caused severe convective weather in the Guanzhong Plain, but their intensities, moving speeds and impact ranges were quite different. The difference characteristics and main reasons of the two down-to-hill thunderstorms are analyzed by using the ERA5 reanalysis data and multiple observation data. The results show that the “7·26” thunderstorm was highly organized, with a long lifespan and the maximum temperature change of 16℃·h-1 within the cold pool, thus resulting in a wide range of short-time severe rainfall and thunderstorm gale. By contrast, the “7·29” storm was dominated by isolated thunderstorm cells, and the maximum temperature change of the cold pool was 8℃·h-1, which only caused the localized short-time severe rainfall along the Qinling Mountains. The “7·26” thunderstorm occurred on the northwest side of the subtropical high, the warm advection development of the middle and low layers increased the unstable energy, the upwelling movement in Guanzhong Plain and the uplift effect of the topography of Beishan provided favorable dynamic conditions for the development of thunderstorms after they moved in. However, the “7·29” storm occurred on the south side of the subtropical high and the downdraft in Guanzhong Plain was not conducive to the development of convection after the storms move in. The moving direction of the “7·26” gust front was opposite to the wind direction in the bounary layer, but parallel to the average wind direction of the storm bearing layer, which was beneficial to the convection vertical development. The low-level vertical wind shear strengthened gradually, increasing synchronously with the strength of cold pool in the course of convection development. The movement direction of the “7·29” gust front was the same as the wind direction of the boundary layer, the low-level convergence was weak, and the 0-3 km wind vector difference was always less than 5 m·s-1 during the whole process, which was not conducive to the development of convection.The special terrain affected the movement direction and intensity of the cold pool. The strong southwest outflow during the “7·26” process made the cold pool move forward along the southern boundary of the plain in a narrow strip from southwest to northeast, the cold pool was concentrated and moved fast, and the strong convergence triggered the development of new convection. During the “7·29” process, the cold pool spread in the terrain transition area of the loess tableland, and the outflow of southeast wind and southwest wind split the convection. The intensity of the cold pool was constantly weakened, which was not favourable for the development of new convection.
On 26 July 2018 (shortly for “7·26”) and 29 July 2018 (shortly for “7·29”), the gust front formed by the cold outflow caused severe convective weather in the Guanzhong Plain, but their intensities, moving speeds and impact ranges were quite different. The difference characteristics and main reasons of the two down-to-hill thunderstorms are analyzed by using the ERA5 reanalysis data and multiple observation data. The results show that the “7·26” thunderstorm was highly organized, with a long lifespan and the maximum temperature change of 16℃·h-1 within the cold pool, thus resulting in a wide range of short-time severe rainfall and thunderstorm gale. By contrast, the “7·29” storm was dominated by isolated thunderstorm cells, and the maximum temperature change of the cold pool was 8℃·h-1, which only caused the localized short-time severe rainfall along the Qinling Mountains. The “7·26” thunderstorm occurred on the northwest side of the subtropical high, the warm advection development of the middle and low layers increased the unstable energy, the upwelling movement in Guanzhong Plain and the uplift effect of the topography of Beishan provided favorable dynamic conditions for the development of thunderstorms after they moved in. However, the “7·29” storm occurred on the south side of the subtropical high and the downdraft in Guanzhong Plain was not conducive to the development of convection after the storms move in. The moving direction of the “7·26” gust front was opposite to the wind direction in the bounary layer, but parallel to the average wind direction of the storm bearing layer, which was beneficial to the convection vertical development. The low-level vertical wind shear strengthened gradually, increasing synchronously with the strength of cold pool in the course of convection development. The movement direction of the “7·29” gust front was the same as the wind direction of the boundary layer, the low-level convergence was weak, and the 0-3 km wind vector difference was always less than 5 m·s-1 during the whole process, which was not conducive to the development of convection.The special terrain affected the movement direction and intensity of the cold pool. The strong southwest outflow during the “7·26” process made the cold pool move forward along the southern boundary of the plain in a narrow strip from southwest to northeast, the cold pool was concentrated and moved fast, and the strong convergence triggered the development of new convection. During the “7·29” process, the cold pool spread in the terrain transition area of the loess tableland, and the outflow of southeast wind and southwest wind split the convection. The intensity of the cold pool was constantly weakened, which was not favourable for the development of new convection.
2023, 49(8):946-957.
DOI: 10.7519/j.issn.1000-0526.2023.052601
Abstract:
Based on air temperature observation data of automatic weather stations in Shaanxi Province, by using sliding training period and unitary linear regression methods, air temperature from CMA Land Data Assimilation System (CLDAS)〖JP2〗 is tested and corrected at stations, then the correction coefficient is interpolated〖JP〗 to grid point to revise CLDAS temperature at the grid. Finally, temperature forecast from European Centre for MediumRange Weather Forecasting (ECMWF) is corrected by respectively using the air temperature data from observation and CLDAS before and after correcting, which is tested by nonindependent and independent validations. The results show that spatial distribution characteristics of temperature from CLDAS are basically consistent with those from station observations, but there are some errors between them, which can be reduced by correcting with observation data. The accuracies of absolute error less than 1℃ or 2℃ of CLDAS temperature before correcting are respectively less than 20% and 30% in Qinling and Daba Mountains, where accuracies are smaller than in other areas and are improved by more than 40% after correction. The CLDAS grid temperature data after correcting are used to correct the temperature prediction of ECMWF improving the accuracy of the model forecasts. It also improves the temperature forecast quality of ECMWF in the areas with few weather stations, and is suitable for high resolution meteorological grid forecast. The accuracies of absolute error less than 2℃ for daily maximum and minimum temperatures with 24 h lead time are increased from 46% and 66% before correcting to 63% and 74% after correcting in Shaanxi Province. These correction effects are higher than accuracies of the temperature forecast corrected by using air temperature data from observation and unrevised CLDAS.
Based on air temperature observation data of automatic weather stations in Shaanxi Province, by using sliding training period and unitary linear regression methods, air temperature from CMA Land Data Assimilation System (CLDAS)〖JP2〗 is tested and corrected at stations, then the correction coefficient is interpolated〖JP〗 to grid point to revise CLDAS temperature at the grid. Finally, temperature forecast from European Centre for MediumRange Weather Forecasting (ECMWF) is corrected by respectively using the air temperature data from observation and CLDAS before and after correcting, which is tested by nonindependent and independent validations. The results show that spatial distribution characteristics of temperature from CLDAS are basically consistent with those from station observations, but there are some errors between them, which can be reduced by correcting with observation data. The accuracies of absolute error less than 1℃ or 2℃ of CLDAS temperature before correcting are respectively less than 20% and 30% in Qinling and Daba Mountains, where accuracies are smaller than in other areas and are improved by more than 40% after correction. The CLDAS grid temperature data after correcting are used to correct the temperature prediction of ECMWF improving the accuracy of the model forecasts. It also improves the temperature forecast quality of ECMWF in the areas with few weather stations, and is suitable for high resolution meteorological grid forecast. The accuracies of absolute error less than 2℃ for daily maximum and minimum temperatures with 24 h lead time are increased from 46% and 66% before correcting to 63% and 74% after correcting in Shaanxi Province. These correction effects are higher than accuracies of the temperature forecast corrected by using air temperature data from observation and unrevised CLDAS.
SUN Xiaoshen
,
ZHOU Xuesi
,
FAN Rong
,
WANG Xiaoqing
,
ZHANG Xiaorui
,
WANG Wuyi
,
XUE Xuewu
,
LI Zhenghao
2023, 49(8):958-971.
DOI: 10.7519/j.issn.1000-0526.2023.071001
Abstract:
A snowfall event occurred in Zhangjiakou in 29-30 November 2019. The snowfall clouds were thoroughly analyzed based on millimeter-wavelength cloud radar observations and aircraft observations to explore the macro- and microphysical characteristics of the clouds. This snowfall event lasted from 14:00 BT 29 to 01:00 BT 30. Restricted by moisture transport and supply, the ground precipitation showed an increasing-decreasing-increasing tendency. The vertical depth of clouds varied distinctly with time. The maximum reflectivity of cloud radar was 25 dBz. The recorded time with ground precipitation more than 1 mm corresponded well to the period that cloud radar detected high values of reflectivity (10-15 dBz) and spectral width. The growing ice crystals and updraft air flows mainly existed above 4000 m. Positive values of radical velocity detected by cloud radar were mostly in mid-to-early stages of snowfall. Ice crystals were the dominated particles within clouds according to the sounding of airborne probes. Besides, graupels and aggregated particles were captured. As ice crystals〖JP2〗 were falling, they grew up through the microphysical processes of coalescence-collision and contact-freezing. Meanwhile the cloud radar observed magnitude of both radical velocity and spectral width were augmented. When ice crystals larger than 500 μm were detected, the reflectivity of cloud radar was greater than 0 dBz. In the heights 4400-4700 m, spectral width of cloud radar dramatically changed. These results could further help understand and analyze the macro-and microphysics of winter snowfall clouds and snowfall enhancement potentials in Zhangjiakou Region.
A snowfall event occurred in Zhangjiakou in 29-30 November 2019. The snowfall clouds were thoroughly analyzed based on millimeter-wavelength cloud radar observations and aircraft observations to explore the macro- and microphysical characteristics of the clouds. This snowfall event lasted from 14:00 BT 29 to 01:00 BT 30. Restricted by moisture transport and supply, the ground precipitation showed an increasing-decreasing-increasing tendency. The vertical depth of clouds varied distinctly with time. The maximum reflectivity of cloud radar was 25 dBz. The recorded time with ground precipitation more than 1 mm corresponded well to the period that cloud radar detected high values of reflectivity (10-15 dBz) and spectral width. The growing ice crystals and updraft air flows mainly existed above 4000 m. Positive values of radical velocity detected by cloud radar were mostly in mid-to-early stages of snowfall. Ice crystals were the dominated particles within clouds according to the sounding of airborne probes. Besides, graupels and aggregated particles were captured. As ice crystals〖JP2〗 were falling, they grew up through the microphysical processes of coalescence-collision and contact-freezing. Meanwhile the cloud radar observed magnitude of both radical velocity and spectral width were augmented. When ice crystals larger than 500 μm were detected, the reflectivity of cloud radar was greater than 0 dBz. In the heights 4400-4700 m, spectral width of cloud radar dramatically changed. These results could further help understand and analyze the macro-and microphysics of winter snowfall clouds and snowfall enhancement potentials in Zhangjiakou Region.
SUN Yanhui
,
ZHANG Bo
,
LIU Wei
,
LIU Changli
,
Huang Wenzhen
,
LIU Zhenghui
,
BAO Xinghua
,
SHOU Shaowen
,
SUN Pengbiao
2023, 49(8):972-984.
DOI: 10.7519/j.issn.1000-0526.2023.042001
Abstract:
Ice on airplanes can cause serious accidents. In order to understand the characteristics and mechanism of natural freezing of aircraft under the background of cold vortex, seven flight detections were conducted using Y-12 aircraft under the upper-air cold vortex in Hulunbuir in May 2021. Among the seven flight detections, two moderate and two intense ice accumulation occurred. This paper discusses the atmospheric environments suitable for aircraft icing detection. Characteristics and mechanism of aircraft icing are speculated based on data obtained from the Droplet Measurement Technologies, Inc. (DMT) equipments carried by the aircraft for the two intense aircraft icing processes on 31 May 2021. The results show that while the aircraft was flying at altitudes of about 3.5-4.2 km, with 〖JP2〗the ambient temperature of -8-〖JP〗-4℃, intense aircraft ice accumulation occurred in the water vapor saturated area in the southeast of the cold vortex. The averaged supercooled liquid water content （LWC） during the high LWC value periods could reach as high as 0.25-1.04 g·m-3, leading to instantaneously aircraft icing, and the particle number concentration increased to 100-200 cm-3 for drops and ice particles with mean effective drop diameter in the range of 15-100 μm. Particle images and their growth patterns in the southeast of the cold vortex were brought out. Finally, the atmospheric icing conditions in the southeast part of the cold vortex are discussed.
Ice on airplanes can cause serious accidents. In order to understand the characteristics and mechanism of natural freezing of aircraft under the background of cold vortex, seven flight detections were conducted using Y-12 aircraft under the upper-air cold vortex in Hulunbuir in May 2021. Among the seven flight detections, two moderate and two intense ice accumulation occurred. This paper discusses the atmospheric environments suitable for aircraft icing detection. Characteristics and mechanism of aircraft icing are speculated based on data obtained from the Droplet Measurement Technologies, Inc. (DMT) equipments carried by the aircraft for the two intense aircraft icing processes on 31 May 2021. The results show that while the aircraft was flying at altitudes of about 3.5-4.2 km, with 〖JP2〗the ambient temperature of -8-〖JP〗-4℃, intense aircraft ice accumulation occurred in the water vapor saturated area in the southeast of the cold vortex. The averaged supercooled liquid water content （LWC） during the high LWC value periods could reach as high as 0.25-1.04 g·m-3, leading to instantaneously aircraft icing, and the particle number concentration increased to 100-200 cm-3 for drops and ice particles with mean effective drop diameter in the range of 15-100 μm. Particle images and their growth patterns in the southeast of the cold vortex were brought out. Finally, the atmospheric icing conditions in the southeast part of the cold vortex are discussed.
2023, 49(8):985-994.
DOI: 10.7519/j.issn.1000-0526.2023.050601
Abstract:
In order to study the influence of two kinds of cloud seeding agents, glaciogenic agents and hygroscopic agents, which are widely used in weather modification, on microphysical characteristics of aerosol particles produced by combustion in natural atmosphere, an experimental study on the combustion of seeding agents for cold and warm cloud seeding in clear sky was carried out based on a weather modification aircraft equipped with aerosol and cloud condensation nuclei (CCN) observation equipment. The results show that the airborne detection equipment could not get the microphysical changes of aerosol particles and CCN before and after the combustion of glaciogenic agent due to the limited observation scale of the aerosol equipment. However, after the combustion of hygroscopic agents, we found that the aerosol and CCN particle number concentrations increased significantly, reaching 1772.4 cm-3 and 1809.01 cm-3 respectively, which were more than 4 times of those values before the hygroscopic agents combustion. Most of the aerosol particles’ sizes were below 0.5 μm with peak diameters decreasing from 0.17 μm before seeding to 0.14 μm after seeding, and the peak value of particle spectrum was 4.8 times of that before combustion, so it had the significant characteristics of forming CCN. Based on the observation results, the nucleation rate after flame catalytic combustion and the new catalytic ways are discussed. The method used in this aircraft experiment could provide scientific references for further studying the physical and chemical characteristics of the particles generated by combustion of cloud seeding agents. Furthermore, the research results could provide objective initial field data support for the establishment of cloud catalytic models, especially for warm cloud catalytic models.
In order to study the influence of two kinds of cloud seeding agents, glaciogenic agents and hygroscopic agents, which are widely used in weather modification, on microphysical characteristics of aerosol particles produced by combustion in natural atmosphere, an experimental study on the combustion of seeding agents for cold and warm cloud seeding in clear sky was carried out based on a weather modification aircraft equipped with aerosol and cloud condensation nuclei (CCN) observation equipment. The results show that the airborne detection equipment could not get the microphysical changes of aerosol particles and CCN before and after the combustion of glaciogenic agent due to the limited observation scale of the aerosol equipment. However, after the combustion of hygroscopic agents, we found that the aerosol and CCN particle number concentrations increased significantly, reaching 1772.4 cm-3 and 1809.01 cm-3 respectively, which were more than 4 times of those values before the hygroscopic agents combustion. Most of the aerosol particles’ sizes were below 0.5 μm with peak diameters decreasing from 0.17 μm before seeding to 0.14 μm after seeding, and the peak value of particle spectrum was 4.8 times of that before combustion, so it had the significant characteristics of forming CCN. Based on the observation results, the nucleation rate after flame catalytic combustion and the new catalytic ways are discussed. The method used in this aircraft experiment could provide scientific references for further studying the physical and chemical characteristics of the particles generated by combustion of cloud seeding agents. Furthermore, the research results could provide objective initial field data support for the establishment of cloud catalytic models, especially for warm cloud catalytic models.
2023, 49(8):995-1004.
DOI: 10.7519/j.issn.1000-0526.2023.062701
Abstract:
Shanxi Province organized an hail suppression by anti-hail gun test on the afternoon of 8 July 2021 in Xixian County of Linfen City. This paper uses phased-array radar data from the Xixian County to analyse the dynamical effects following shelling of severe convective clouds. First of all, through the analysis of composite reflectivity, it can be seen that the operation time and position of this operation were in line with the test design. In other words, the explosion was during the natural cloud development period and the blast point was located at the upper end of the strong echo column. The location of the shell blast point in the test was estimated from the operational information and ballistic curve. The change in radar parameters in the neighborhood of the blast point before and after the operation is analyzed after the spatio-temporal consistency conversion of radar, shell point and blast point. The results show that the strong echo column was developing and intensifying in 3-0 min before the operation, and there was no Doppler spectrum wide area near the predetermined explosion point. After the operation, at the lower end of the blast site, the strong echo column rapidly weakened, split and sank, showing a significant broadening of the Doppler spectrum in the neighborhood of the blast site area. The broadening was maintained for 2-3 min, eventually leading to the overall decay of the strong echo without re-enhancement. This evolution scenario shows an effect chain: the transition from a strong echo column to a decaying one begins at the blast site after the explosion. The dynamical disturbance induced by the explosion metamorphoses into a secondary flow that broadens the Doppler spectrum, and the Reynolds stress induced by the inhomogeneous dynamical disturbance field suppresses the convective flow field, finally causing the overall decay of the convective cloud. In addition, the statistics of the top heights of the echoes and the number of echo samples of different intensities show that the top heights of the strong echoes decrease rapidly after the explosion and the corresponding number of pixels decreases 〖JP2〗rapidly. The value of the weak echo pixels increases as the strong echoes decrease and finally the value of the echo pixels decreases over time for all intensities.
Shanxi Province organized an hail suppression by anti-hail gun test on the afternoon of 8 July 2021 in Xixian County of Linfen City. This paper uses phased-array radar data from the Xixian County to analyse the dynamical effects following shelling of severe convective clouds. First of all, through the analysis of composite reflectivity, it can be seen that the operation time and position of this operation were in line with the test design. In other words, the explosion was during the natural cloud development period and the blast point was located at the upper end of the strong echo column. The location of the shell blast point in the test was estimated from the operational information and ballistic curve. The change in radar parameters in the neighborhood of the blast point before and after the operation is analyzed after the spatio-temporal consistency conversion of radar, shell point and blast point. The results show that the strong echo column was developing and intensifying in 3-0 min before the operation, and there was no Doppler spectrum wide area near the predetermined explosion point. After the operation, at the lower end of the blast site, the strong echo column rapidly weakened, split and sank, showing a significant broadening of the Doppler spectrum in the neighborhood of the blast site area. The broadening was maintained for 2-3 min, eventually leading to the overall decay of the strong echo without re-enhancement. This evolution scenario shows an effect chain: the transition from a strong echo column to a decaying one begins at the blast site after the explosion. The dynamical disturbance induced by the explosion metamorphoses into a secondary flow that broadens the Doppler spectrum, and the Reynolds stress induced by the inhomogeneous dynamical disturbance field suppresses the convective flow field, finally causing the overall decay of the convective cloud. In addition, the statistics of the top heights of the echoes and the number of echo samples of different intensities show that the top heights of the strong echoes decrease rapidly after the explosion and the corresponding number of pixels decreases 〖JP2〗rapidly. The value of the weak echo pixels increases as the strong echoes decrease and finally the value of the echo pixels decreases over time for all intensities.
2023, 49(8):1005-1019.
DOI: 10.7519/j.issn.1000-0526.2023.051101
Abstract:
Based on the Tropical Cyclones Best Track Dataset for the Western North Pacific compiled by the Shanghai Typhoon Institute of China Meteorological Administration (CMA), the positioning errors and intensity estimation errors as well as the track, intensity and landfall forecast errors of the 22 named typhoons over Western North Pacific and South China Sea in 2021 are evaluated. The verification results show that the average positioning error of typhoons made by the National Meteorological Centre, CMA, in 2021 was 19.7 km, which was 13% less than that of 2020 (22.7 km). 〖JP2〗The average intensity estimation error was 1.4 m·s-1, which was slightly higher than that of 2020 (1.2 m·s-1). The average annual track forecast errors of the official typhoon forecast agencies, global models, and regional models at home and abroad have increased compared to the errors in 2020, and the average track forecast errors of subjective and objective forecasting methods failed to have a continuous decreasing trend in 2012-2021. The mean absolute errors of intensity forecasts of all forecasting methods have generally decreased to some extent from 2012 to 2017, but did not show a decreasing trend in 2018-2021. The subjective and objective forecasting methods generally performed well in forecasting the 24 h landfall points for the typhoons Koguma, InFa, Cempaka, Lionrock and Kompasu.
Based on the Tropical Cyclones Best Track Dataset for the Western North Pacific compiled by the Shanghai Typhoon Institute of China Meteorological Administration (CMA), the positioning errors and intensity estimation errors as well as the track, intensity and landfall forecast errors of the 22 named typhoons over Western North Pacific and South China Sea in 2021 are evaluated. The verification results show that the average positioning error of typhoons made by the National Meteorological Centre, CMA, in 2021 was 19.7 km, which was 13% less than that of 2020 (22.7 km). 〖JP2〗The average intensity estimation error was 1.4 m·s-1, which was slightly higher than that of 2020 (1.2 m·s-1). The average annual track forecast errors of the official typhoon forecast agencies, global models, and regional models at home and abroad have increased compared to the errors in 2020, and the average track forecast errors of subjective and objective forecasting methods failed to have a continuous decreasing trend in 2012-2021. The mean absolute errors of intensity forecasts of all forecasting methods have generally decreased to some extent from 2012 to 2017, but did not show a decreasing trend in 2018-2021. The subjective and objective forecasting methods generally performed well in forecasting the 24 h landfall points for the typhoons Koguma, InFa, Cempaka, Lionrock and Kompasu.
2023, 49(8):1020-1028.
DOI: 10.7519/j.issn.1000-0526.2023.070601
Abstract:
The main characteristics of the general atmospheric circulation in May 2023 are that the polar vortex in the Northern Hemisphere was mono-polar with stronger intensity than usual. The 500 hPa geopotential height presented the distribution of a four-wave pattern in middle-high latitudes of the Northern Hemisphere, which means that the circulation have transformed from a three-wave pattern in winter to a four-wave pattern in summer. The Western Pacific subtropical high was stronger than that of normal years. The monthly mean temperature across China was 16.3℃， 0.2℃ lower than normal. The monthly mean precipitation was 57.8 mm, 18% less than normal. During this month five torrential rainfall processes occurred in China. After the onset of the South China Sea summer monsoon in the third pentad, precipitation occurred in southwestern China， alleviating the drought in Yunnan Province. In addition, China experienced five severe convection weather events, making local areas suffer hail disasters. Besides, three sand-dust events were seen in northern China.
The main characteristics of the general atmospheric circulation in May 2023 are that the polar vortex in the Northern Hemisphere was mono-polar with stronger intensity than usual. The 500 hPa geopotential height presented the distribution of a four-wave pattern in middle-high latitudes of the Northern Hemisphere, which means that the circulation have transformed from a three-wave pattern in winter to a four-wave pattern in summer. The Western Pacific subtropical high was stronger than that of normal years. The monthly mean temperature across China was 16.3℃， 0.2℃ lower than normal. The monthly mean precipitation was 57.8 mm, 18% less than normal. During this month five torrential rainfall processes occurred in China. After the onset of the South China Sea summer monsoon in the third pentad, precipitation occurred in southwestern China， alleviating the drought in Yunnan Province. In addition, China experienced five severe convection weather events, making local areas suffer hail disasters. Besides, three sand-dust events were seen in northern China.
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ISSN:1000-0526 CN:11-2282/P