ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 48,Issue 2,2022 Table of Contents
2022, 48(2):129-148.
DOI: 10.7519/j.issn.1000-0526.2021.092901
Abstract:
Winter sports are closely related to meteorological conditions, which is one of the most important factors for the success of Winter Olympic Games. According to the meteorological support requirements of Beijing Winter Olympic Games, CMA Earth System Modeling and Prediction Centre has preliminarily established a high-resolution regional ensemble prediction test system based on the multi-scale blending (MSB) initial condition perturbation method and lateral boundary condition (LBC) perturbation method, and carried out continuous tests for the same period corresponding to the 2022 Beijing Winter Olympic Games. The statistical results of the preliminary test show that the root mean square error of the ensemble mean values of isobaric surface elements at high, medium and low layers of the main forecast variables is basically less than or equal to the control forecast error, which reflects the advantages of the ensemble mean over the single deterministic forecast. The forecast effect of surface element wind and precipitation is good, but the deviation of 24 h temperature forecast is 2 ℃ higher, which is far from the accurate Winter Olympic Games meteorological support. The high-resolution regional ensemble forecast synoptic analysis of two cold waves and strong wind processes during the test period shows that the ensemble forecast products can accurately describe the main distribution characteristics of ground temperature, cold wave movement process and precipitation forecast, and provide valuable probabilistic forecast information for forecasters, such as cold wave standard 24 h varying temperature forecast and gale forecast. Based on the diagnostic method, the weather element ensemble forecast products that have an important impact on the operation of Winter Olympic events and athletes’ performance such as visibility, strong wind and precipitation phase are developed. The preliminary test results show that the choice of different ensemble members is sensitive to the visibility forecast, and has a certain forecast ability, but the forecast range is too large, and the value is low, which needs to be further improved. The distribution of gust forecast is consistent with the actual large-value area. The precipitation phase forecast is consistent with the observed distribution, especially the boundary of rain and snow, and the location ranges of rainfall, sleet, snow and ice particles are reasonable, which further improves the meteorological support ability to the Beijing Winter Olympic Games.
Winter sports are closely related to meteorological conditions, which is one of the most important factors for the success of Winter Olympic Games. According to the meteorological support requirements of Beijing Winter Olympic Games, CMA Earth System Modeling and Prediction Centre has preliminarily established a high-resolution regional ensemble prediction test system based on the multi-scale blending (MSB) initial condition perturbation method and lateral boundary condition (LBC) perturbation method, and carried out continuous tests for the same period corresponding to the 2022 Beijing Winter Olympic Games. The statistical results of the preliminary test show that the root mean square error of the ensemble mean values of isobaric surface elements at high, medium and low layers of the main forecast variables is basically less than or equal to the control forecast error, which reflects the advantages of the ensemble mean over the single deterministic forecast. The forecast effect of surface element wind and precipitation is good, but the deviation of 24 h temperature forecast is 2 ℃ higher, which is far from the accurate Winter Olympic Games meteorological support. The high-resolution regional ensemble forecast synoptic analysis of two cold waves and strong wind processes during the test period shows that the ensemble forecast products can accurately describe the main distribution characteristics of ground temperature, cold wave movement process and precipitation forecast, and provide valuable probabilistic forecast information for forecasters, such as cold wave standard 24 h varying temperature forecast and gale forecast. Based on the diagnostic method, the weather element ensemble forecast products that have an important impact on the operation of Winter Olympic events and athletes’ performance such as visibility, strong wind and precipitation phase are developed. The preliminary test results show that the choice of different ensemble members is sensitive to the visibility forecast, and has a certain forecast ability, but the forecast range is too large, and the value is low, which needs to be further improved. The distribution of gust forecast is consistent with the actual large-value area. The precipitation phase forecast is consistent with the observed distribution, especially the boundary of rain and snow, and the location ranges of rainfall, sleet, snow and ice particles are reasonable, which further improves the meteorological support ability to the Beijing Winter Olympic Games.
2022, 48(2):149-161.
DOI: 10.7519/j.issn.1000-0526.2022.010301
Abstract:
Based on multi-source observation data during January-March in 2019, the spatio-temporal distribution characteristics of temperature and wind in Zhangjiakou Olympic Area for the Beijing 2022 Olympic and Paralympic Winter Games are analyzed, especially for their diurnal variations under different synoptic backgrounds. It is shown that the characteristics of temperature and wind are affected both by differences in solar radiation and topographic altitudes. Additionally, the diurnal temperature range in the basin or valley, where temperature inversion phenomena are frequently observed, is significantly larger than that on the mountain top. Meanwhile, temperature inversion intensity is closely related to daily temperature changes and background winds, and the extent of temperature inversion tends to be deeper as environmental wind speed decreases. On the other hand, diurnal variations of wind speed can be clearly seen in the studied area. Winds tend to strengthen in the daytime and reach their peaks in the afternoon, and minimum winds appear at night on average. Local and thermally-driven circulations are dominant under weak synoptic patterns. An obvious shift in wind direction between day and night can be seen in Guyangshu Basin but not in Genting Snow Park. At the same time, cold air tends to accumulate at the basin bottom on nightfall and bring temperature inversion phenomena in the basin, which usually reach their peaks before sunrise and weaken or disappear rapidly after sunrise under weak synoptic circumstances. It is observed that the extent of temperature inversion in Guyangshu Basin is much greater than that in Genting Snow Park. However, there seems to be no diurnal changes in wind direction in both Guyangshu Basin and Genting Snow Park under the influence of cold air, and temperature also decreases monotonously with the increase of altitudes in such a condition.
Based on multi-source observation data during January-March in 2019, the spatio-temporal distribution characteristics of temperature and wind in Zhangjiakou Olympic Area for the Beijing 2022 Olympic and Paralympic Winter Games are analyzed, especially for their diurnal variations under different synoptic backgrounds. It is shown that the characteristics of temperature and wind are affected both by differences in solar radiation and topographic altitudes. Additionally, the diurnal temperature range in the basin or valley, where temperature inversion phenomena are frequently observed, is significantly larger than that on the mountain top. Meanwhile, temperature inversion intensity is closely related to daily temperature changes and background winds, and the extent of temperature inversion tends to be deeper as environmental wind speed decreases. On the other hand, diurnal variations of wind speed can be clearly seen in the studied area. Winds tend to strengthen in the daytime and reach their peaks in the afternoon, and minimum winds appear at night on average. Local and thermally-driven circulations are dominant under weak synoptic patterns. An obvious shift in wind direction between day and night can be seen in Guyangshu Basin but not in Genting Snow Park. At the same time, cold air tends to accumulate at the basin bottom on nightfall and bring temperature inversion phenomena in the basin, which usually reach their peaks before sunrise and weaken or disappear rapidly after sunrise under weak synoptic circumstances. It is observed that the extent of temperature inversion in Guyangshu Basin is much greater than that in Genting Snow Park. However, there seems to be no diurnal changes in wind direction in both Guyangshu Basin and Genting Snow Park under the influence of cold air, and temperature also decreases monotonously with the increase of altitudes in such a condition.
2022, 48(2):162-176.
DOI: 10.7519/j.issn.1000-0526.2021.092902
Abstract:
Almost all numerical prediction models have systematic errors. Although the statistical correction method has achieved some success in reducing the wind speed deviation at individual stations, it is still urgent to develop a high-resolution wind forecast bias correction method under complex terrain based on grid points. In this study, a fusion prediction and correction technique for high-resolution wind field at different altitudes in Winter Olympic Games area under complex terrain is proposed. Firstly, the statistical bias correction method is used to obtain the 1-12 h average systematic deviation of wind at each station by using the wind observation data of 133 automatic weather stations in the Winter Olympic Mountain Competition area and the high-resolution wind forecast data of RMAPS-RISE system. Then the wind of CMA-BJ model is modified by downscaling and optimized by the grid deviation correction coefficient. Finally, the optimized high-resolution wind is modified by incorporating the latest surface observational data. The results show that this method greatly reduces the systematic deviation of wind speed and the average absolute error of wind speed forecast. The reduction rate of the average absolute error and root mean square error of wind speed within 12 hours is more than 40%. With appropriate modification, this method can also be applied to the bias correction of other variables.
Almost all numerical prediction models have systematic errors. Although the statistical correction method has achieved some success in reducing the wind speed deviation at individual stations, it is still urgent to develop a high-resolution wind forecast bias correction method under complex terrain based on grid points. In this study, a fusion prediction and correction technique for high-resolution wind field at different altitudes in Winter Olympic Games area under complex terrain is proposed. Firstly, the statistical bias correction method is used to obtain the 1-12 h average systematic deviation of wind at each station by using the wind observation data of 133 automatic weather stations in the Winter Olympic Mountain Competition area and the high-resolution wind forecast data of RMAPS-RISE system. Then the wind of CMA-BJ model is modified by downscaling and optimized by the grid deviation correction coefficient. Finally, the optimized high-resolution wind is modified by incorporating the latest surface observational data. The results show that this method greatly reduces the systematic deviation of wind speed and the average absolute error of wind speed forecast. The reduction rate of the average absolute error and root mean square error of wind speed within 12 hours is more than 40%. With appropriate modification, this method can also be applied to the bias correction of other variables.
2022, 48(2):177-189.
DOI: 10.7519/j.issn.1000-0526.2022.010401
Abstract:
Based on observation data from 11 meteorological stations from January to March of 2019-2020 over the Yanqing Area of the 2022 Beijing Winter Olympic Games, spatio-temporal distributions of wind field and temperature are analyzed, and the correlation of gust factor with mean wind speed and turbulence intensity is established, so as to provide a reference for forecasting temperature and wind field in the complex terrain area, especially for the gust wind forecast. Generally, the daily high temperature occurs at 15:00 BT or 16:00 BT and the lowest temperature appears from 06:00 BT to 08:00 BT. Furthermore, the range of diurnal temperature decreases with the increase of altitude. The mean wind speed and wind gust have similar characteristics of diurnal variation. Taking S5 as the boundary, the winds at higher-altitude stations are relatively weaker in the daytime than at nighttime, while the diurnal variations of wind speeds at lower-altitude stations are opposite. Wind speeds at the stations with altitude above 1 〖KG-*5〗900 m usually increase with altitude. The wind direction at stations over mountain tops have no diurnal variation with a dominant direction of northwesterly. However, the wind directions at stations in the mountainsides and low-elevation areas are characterized by diurnal variation. Wind direction variation of the former is less noticeable, with the prevailing northwesterly in the daytime and westerly at nighttime, while the latter shows significant variation with a feature of mountain-valley breeze. The gust factor at S1 station has obvious diurnal variation with maximum value and large variation in the afternoon and relatively small value and lower spread at night. Finally, the linear relationship between the gust factor and turbulence intensity is established, and the gust factor based on turbulence intensity fitting is closer to the observed factor.
Based on observation data from 11 meteorological stations from January to March of 2019-2020 over the Yanqing Area of the 2022 Beijing Winter Olympic Games, spatio-temporal distributions of wind field and temperature are analyzed, and the correlation of gust factor with mean wind speed and turbulence intensity is established, so as to provide a reference for forecasting temperature and wind field in the complex terrain area, especially for the gust wind forecast. Generally, the daily high temperature occurs at 15:00 BT or 16:00 BT and the lowest temperature appears from 06:00 BT to 08:00 BT. Furthermore, the range of diurnal temperature decreases with the increase of altitude. The mean wind speed and wind gust have similar characteristics of diurnal variation. Taking S5 as the boundary, the winds at higher-altitude stations are relatively weaker in the daytime than at nighttime, while the diurnal variations of wind speeds at lower-altitude stations are opposite. Wind speeds at the stations with altitude above 1 〖KG-*5〗900 m usually increase with altitude. The wind direction at stations over mountain tops have no diurnal variation with a dominant direction of northwesterly. However, the wind directions at stations in the mountainsides and low-elevation areas are characterized by diurnal variation. Wind direction variation of the former is less noticeable, with the prevailing northwesterly in the daytime and westerly at nighttime, while the latter shows significant variation with a feature of mountain-valley breeze. The gust factor at S1 station has obvious diurnal variation with maximum value and large variation in the afternoon and relatively small value and lower spread at night. Finally, the linear relationship between the gust factor and turbulence intensity is established, and the gust factor based on turbulence intensity fitting is closer to the observed factor.
2022, 48(2):190-202.
DOI: 10.7519/j.issn.1000-0526.2021.112101
Abstract:
By using the conventional observation, automatic station, Doppler radar and FNL reanalysis data (1°×1°)， this paper analyzes the spatial and temporal distribution characteristics, ambient conditions and radar key features of the typhoon-tornadoes in Jiangsu during the 2007-2018, and compares with the corresponding characteristics of typhoon-tornadoes in Guangdong. The analysis results indicate that the frequency of typhoon-tornadoes in Jiangsu has increased compared with the past, and the occurrence time of the tornadoes is concentrated in July and August from 16:00 BT to 20:00 BT. Jiangsu typhoon-tornadoes occur after typhoon landfall 24 hours later, different from Guangdong typhoon-tornadoes, which occur within 24 hours after typhoon makes landfall. A strong preference for tornado occurrence is in the northeast quadrant with respect to land-falling typhoon center. High risk areas of tornado occurrence in Jiangsu are concentrated in the central part of Jianghuai and Xuzhou. The low-level jet transports abundant water vapor and unstable energy, providing favorable ambient conditions for tornado, and the ground convergence line is an important system for tornado development. The common ambient conditions for Jiangsu and Guangdong tornadoes appear to be the low, strong deep-layer and low-level vertical wind shear and high storm relative helicity. The major difference between the Jiangsu and Guangdong tornado cases is that the Guangdong tornado has weaker convective available potential energy and convective inhibition and much lower lifting condensation level, but stronger deep-layer and low-level vertical wind shear. About 2/3 of typhoon tornadoes in Jiangsu accompany with tornadic vortex signature （TVS）. The thunderstorm cells that produce strong tornadoes are associated with mesocyclone and TVS. Strong tornado is more likely to occur when the lowest level difference velocity of TVS exceeds 23 m·s-1. The lowest level difference velocity of tornado TVS in Jiangsu is weaker, and the maximum shear is smaller (1/3 of that in Guangdong).
By using the conventional observation, automatic station, Doppler radar and FNL reanalysis data (1°×1°)， this paper analyzes the spatial and temporal distribution characteristics, ambient conditions and radar key features of the typhoon-tornadoes in Jiangsu during the 2007-2018, and compares with the corresponding characteristics of typhoon-tornadoes in Guangdong. The analysis results indicate that the frequency of typhoon-tornadoes in Jiangsu has increased compared with the past, and the occurrence time of the tornadoes is concentrated in July and August from 16:00 BT to 20:00 BT. Jiangsu typhoon-tornadoes occur after typhoon landfall 24 hours later, different from Guangdong typhoon-tornadoes, which occur within 24 hours after typhoon makes landfall. A strong preference for tornado occurrence is in the northeast quadrant with respect to land-falling typhoon center. High risk areas of tornado occurrence in Jiangsu are concentrated in the central part of Jianghuai and Xuzhou. The low-level jet transports abundant water vapor and unstable energy, providing favorable ambient conditions for tornado, and the ground convergence line is an important system for tornado development. The common ambient conditions for Jiangsu and Guangdong tornadoes appear to be the low, strong deep-layer and low-level vertical wind shear and high storm relative helicity. The major difference between the Jiangsu and Guangdong tornado cases is that the Guangdong tornado has weaker convective available potential energy and convective inhibition and much lower lifting condensation level, but stronger deep-layer and low-level vertical wind shear. About 2/3 of typhoon tornadoes in Jiangsu accompany with tornadic vortex signature （TVS）. The thunderstorm cells that produce strong tornadoes are associated with mesocyclone and TVS. Strong tornado is more likely to occur when the lowest level difference velocity of TVS exceeds 23 m·s-1. The lowest level difference velocity of tornado TVS in Jiangsu is weaker, and the maximum shear is smaller (1/3 of that in Guangdong).
2022, 48(2):203-215.
DOI: 10.7519/j.issn.1000-0526.2021.061301
Abstract:
This paper uses sounding data, NCEP reanalysis data and observation data of X-band dual-polarization radar to analyze the hailstorms triggered by small troughs. According to the features of occurrence and development and the predictive indexes with good indicative significance to the hailstorm triggered by small trough, a diagnosis method is constructed. By the method, three hailstorms with different intensities triggered by small trough are diagnosed, and the prediction effects are verified. The results indicate that the hailstorm potential of individual cases can be diagnosed effectively by the thresholds of the vertical helicity of humid heat force greater than 0.8×10-3 Pa·m3·K·kg-1·s-2 and the vertical helicity of water vapor greater than 0.8×10-5 kg-1·m3·Pa·s-2 in the initial stage of hailstone development. Strong wind shear and cell merging processes promote the occurrence and development of hailstorm. In view of this feature, the probability of hailstorm cell developing into severe hailstorm can be diagnosed by using the correspondence between the large value center with the absolute value of thermo shear advection parameter greater than 3×10-8 K·Pa-1·s-1 and the threshold value of the relation between 45 dBz echo top height and 0℃ height. Finally, it is verified that this method can diagnose the hailfall potential and severe hailstorm process comprehensively.
This paper uses sounding data, NCEP reanalysis data and observation data of X-band dual-polarization radar to analyze the hailstorms triggered by small troughs. According to the features of occurrence and development and the predictive indexes with good indicative significance to the hailstorm triggered by small trough, a diagnosis method is constructed. By the method, three hailstorms with different intensities triggered by small trough are diagnosed, and the prediction effects are verified. The results indicate that the hailstorm potential of individual cases can be diagnosed effectively by the thresholds of the vertical helicity of humid heat force greater than 0.8×10-3 Pa·m3·K·kg-1·s-2 and the vertical helicity of water vapor greater than 0.8×10-5 kg-1·m3·Pa·s-2 in the initial stage of hailstone development. Strong wind shear and cell merging processes promote the occurrence and development of hailstorm. In view of this feature, the probability of hailstorm cell developing into severe hailstorm can be diagnosed by using the correspondence between the large value center with the absolute value of thermo shear advection parameter greater than 3×10-8 K·Pa-1·s-1 and the threshold value of the relation between 45 dBz echo top height and 0℃ height. Finally, it is verified that this method can diagnose the hailfall potential and severe hailstorm process comprehensively.
2022, 48(2):216-228.
DOI: 10.7519/j.issn.1000-0526.2021.101801
Abstract:
Based on densely observed snow depth, snow-to-liquid ratio (SLR) of a snowfall event in the plain of central North China on 14 February 2020 is studied. The variation characteristics of SLR and its reasons are discussed. Results show that the SLR increases from Beijing Plain to western Tianjin and then decreases to eastern Tianjin. The maximum value of SLR is located in the western part of Tianjin and there is a big difference of the SLR between Beijing and Tianjin. The 3 h averaged SLR shows that, in eastern plain area of Beijing and in central and northern part of Tianjin, the change of SLR with time is little. In the southern Tianjin and the coastal areas of Tianjin, by contrast, the SLR tends to increase with time. The similar characteristic of the SLR in cloud based on Cobb snow-fall algorithm is also found in west-east direction. This indicates that the process in cloud is the main factor forming the above variation of the SLR in the plain of central North China. The surface and near-surface snowmelt in Beijing intensifies this characteristic due to the higher surface temperature, surface air temperature and the weak warm layer in surface layer. In addition, differences between the SLR based on Cobb and the SLR obtained from snow depth data are analyzed. It is found that the obvious differences occur in central and western part of the research area, especially in the western part. This is related mainly to the snowmelt caused by higher air surface temperature. The difference in the plain area of Beijing basically comes from this. In western Tianjin, the difference comes probably from riming growth induced by co-existing of ice and water in clouds.
Based on densely observed snow depth, snow-to-liquid ratio (SLR) of a snowfall event in the plain of central North China on 14 February 2020 is studied. The variation characteristics of SLR and its reasons are discussed. Results show that the SLR increases from Beijing Plain to western Tianjin and then decreases to eastern Tianjin. The maximum value of SLR is located in the western part of Tianjin and there is a big difference of the SLR between Beijing and Tianjin. The 3 h averaged SLR shows that, in eastern plain area of Beijing and in central and northern part of Tianjin, the change of SLR with time is little. In the southern Tianjin and the coastal areas of Tianjin, by contrast, the SLR tends to increase with time. The similar characteristic of the SLR in cloud based on Cobb snow-fall algorithm is also found in west-east direction. This indicates that the process in cloud is the main factor forming the above variation of the SLR in the plain of central North China. The surface and near-surface snowmelt in Beijing intensifies this characteristic due to the higher surface temperature, surface air temperature and the weak warm layer in surface layer. In addition, differences between the SLR based on Cobb and the SLR obtained from snow depth data are analyzed. It is found that the obvious differences occur in central and western part of the research area, especially in the western part. This is related mainly to the snowmelt caused by higher air surface temperature. The difference in the plain area of Beijing basically comes from this. In western Tianjin, the difference comes probably from riming growth induced by co-existing of ice and water in clouds.
2022, 48(2):229-244.
DOI: 10.7519/j.issn.1000-0526.2021.120101
Abstract:
In order to compare the difference of mesocyclone identifications between S-band dual polarization radar (SPOL) data and X-band phased array weather radar (XPAR) data, based on the SPOL and XPAR and ground observation data, a small and medium scale weather process that occurred in Guangzhou on 19 April 2019 is compared and analyzed. The results show that the identification algorithm used can correctly identify the mesocyclone. The high spatial-temporal resolution data of XPAR can make up for the lack of SPOL elevation layer, and more complete vertical structures of mesocyclones were observed. The parameters in the identification results were more detailed than those in SPOL, which revealed the short-term evolution of mesocyclone more accurately. In conclusion, compared with SPOL, XPAR has the advantages of longer duration, more fine vertical structure, larger difference between positive and negative velocity extremum, and more detailed evolution with the whole weather process. This is conducive to the detailed and in-depth study on the rapid development and evolution of mesoscale weather system.
In order to compare the difference of mesocyclone identifications between S-band dual polarization radar (SPOL) data and X-band phased array weather radar (XPAR) data, based on the SPOL and XPAR and ground observation data, a small and medium scale weather process that occurred in Guangzhou on 19 April 2019 is compared and analyzed. The results show that the identification algorithm used can correctly identify the mesocyclone. The high spatial-temporal resolution data of XPAR can make up for the lack of SPOL elevation layer, and more complete vertical structures of mesocyclones were observed. The parameters in the identification results were more detailed than those in SPOL, which revealed the short-term evolution of mesocyclone more accurately. In conclusion, compared with SPOL, XPAR has the advantages of longer duration, more fine vertical structure, larger difference between positive and negative velocity extremum, and more detailed evolution with the whole weather process. This is conducive to the detailed and in-depth study on the rapid development and evolution of mesoscale weather system.
2022, 48(2):245-253.
DOI: 10.7519/j.issn.1000-0526.2021.060401
Abstract:
Based on the best-track data from Joint Typhoon Warning Center and ERA-interim 1°×1° reanal-ysis data in 1979-2018, this paper investigates the activity characteristics of super cyclonic storms that are formed over the North Indian Ocean in autumn. The results show that the number of super cyclonic storms in autumn over the North Indian Ocean increased significantly after 1998. The average maximum potential intensity (MPI) index of the North Indian Ocean in 1999-2018 was higher than that in 1979-1998. Compared with the conditions in 1979-1998, the higher average sea surface temperature and ocean heat content in 1999-2018 provided favorable conditions for the formation and development of super cyclonic storms. Moreover, weaker vertical wind shear, stronger water vapor flux and lower level cyclonic vorticity transport promoted the sustained growth of cyclonic storm intensity.
Based on the best-track data from Joint Typhoon Warning Center and ERA-interim 1°×1° reanal-ysis data in 1979-2018, this paper investigates the activity characteristics of super cyclonic storms that are formed over the North Indian Ocean in autumn. The results show that the number of super cyclonic storms in autumn over the North Indian Ocean increased significantly after 1998. The average maximum potential intensity (MPI) index of the North Indian Ocean in 1999-2018 was higher than that in 1979-1998. Compared with the conditions in 1979-1998, the higher average sea surface temperature and ocean heat content in 1999-2018 provided favorable conditions for the formation and development of super cyclonic storms. Moreover, weaker vertical wind shear, stronger water vapor flux and lower level cyclonic vorticity transport promoted the sustained growth of cyclonic storm intensity.
2022, 48(2):254-260.
DOI: 10.7519/j.issn.1000-0526.2021.122901
Abstract:
The main characteristics of the general atmospheric circulation in November 2021 are as follows. The polar vortex in the Northern Hemisphere is significantly strong. The Eurasian mid- and high-latitude circulation had a latitudinal multi-fluctuation pattern. Cold air was extremely active. Both East Asian trough and the western Pacific subtropical high were westward and strong. The monthly mean precipitation (23.8 mm) over China was 26.7% more than normal (18.8 mm). The monthly average temperature was 2.9℃, similar to the normal years. Cold and warm temperatures fluctuate greatly during the month. There were two nationwide cold wave processes and three widespread persistent fog-haze weather processes. Among them, the cold wave weather process from 4 to 9 November had the characteristics of a wide range of influence, sharp drop in temperature, long duration of strong winds and extreme blizards in northern China, etc.
The main characteristics of the general atmospheric circulation in November 2021 are as follows. The polar vortex in the Northern Hemisphere is significantly strong. The Eurasian mid- and high-latitude circulation had a latitudinal multi-fluctuation pattern. Cold air was extremely active. Both East Asian trough and the western Pacific subtropical high were westward and strong. The monthly mean precipitation (23.8 mm) over China was 26.7% more than normal (18.8 mm). The monthly average temperature was 2.9℃, similar to the normal years. Cold and warm temperatures fluctuate greatly during the month. There were two nationwide cold wave processes and three widespread persistent fog-haze weather processes. Among them, the cold wave weather process from 4 to 9 November had the characteristics of a wide range of influence, sharp drop in temperature, long duration of strong winds and extreme blizards in northern China, etc.
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ISSN:1000-0526 CN:11-2282/P