ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,Issue 7,2025 Table of Contents
2025, 51(7):773-788.
DOI: 10.7519/j.issn.1000-0526.2024.092401
Abstract:
Thunderstorm gales refer to strong winds with a wind speed ≥17 m·s-1 caused by severe convective weather systems. It is one of mesoscale and microscale severe convective weather causing huge disasters. Understanding their formation mechanisms and conducting accurate nowcasting and early warning are the keys to disaster prevention and mitigation. This article summarizes the existing studies on the formation mechanisms and nowcasting of thunderstorm gales, including synoptic patterns, ambient characteristics, different formation mechanisms and windstorm morphologies, as well as nowcasting technology. It has been found that most thunderstorm gales are generated in supercells, squall lines, and bow echoes through strong downdraft, gust front, momentum transmission, horizontal pressure gradient between outflow and ambient wind, dynamic forcing and superimposed effect of mesoscale vortex, and pumping effect of updraft on low-level warm and moist inflow, etc. On the basis of the above review, the difficulties and much-needed issues of the formation mechanisms and nowcasting of thunderstorm gales are discussed.
Thunderstorm gales refer to strong winds with a wind speed ≥17 m·s-1 caused by severe convective weather systems. It is one of mesoscale and microscale severe convective weather causing huge disasters. Understanding their formation mechanisms and conducting accurate nowcasting and early warning are the keys to disaster prevention and mitigation. This article summarizes the existing studies on the formation mechanisms and nowcasting of thunderstorm gales, including synoptic patterns, ambient characteristics, different formation mechanisms and windstorm morphologies, as well as nowcasting technology. It has been found that most thunderstorm gales are generated in supercells, squall lines, and bow echoes through strong downdraft, gust front, momentum transmission, horizontal pressure gradient between outflow and ambient wind, dynamic forcing and superimposed effect of mesoscale vortex, and pumping effect of updraft on low-level warm and moist inflow, etc. On the basis of the above review, the difficulties and much-needed issues of the formation mechanisms and nowcasting of thunderstorm gales are discussed.
2025, 51(7):789-802.
DOI: 10.7519/j.issn.1000-0526.2025.032901
Abstract:
South China is an important water vapor transport channel. Studying the water vapor budget in South China is essential for predicting precipitation processes in South China and its neighboring areas, and comprehending the impact of atmospheric circulation changes on weather and climate in China. Based on ERA5 data, the variation trend of water vapor budget and its correlation with precipitation in South China during the recent 40 years (1983-2022) are analyzed. The results show that water vapor in South China is mainly input through its the southern and western boundaries, and output through the northern and eastern boundaries, with the net budget being negative. The water vapor budget shows a declining trend, with a significant decrease in the output from the eastern boundary. In the four seasons, the input and output water vapor budget declines most obviously in spring. Water vapor enters into the South China Region mainly from the Indian Ocean and the Bay of Bengal in the southwest direction and western Pacific in the southwest direction. Water vapor in the middle and lower layers (700 hPa) is primarily transported from the Indian Ocean and the Bay of Bengal, while water vapor in the lower layer (925 hPa) mainly originates from western Pacific. In the recent 40 years, water vapor transport from the Indian Ocean and the Bay of Bengal and western Pacific has been weakening, causing the changes in water vapor transport from the direction of northeast to southwest in South China. Water vapor transport is positively correlated to precipitation in most areas of Guangxi and Guangdong, with correlation coefficient >0.6, of which the strengthening of southwestly water vapor transport is the key reason of precipitation. In addition, there is a trend of wetting in South China, with a 2.32% increase in precipitable water vapor (PWV) during the recent 40 years, which is the result of decrease in total water vapor outflow in the region than that of total inflow. The results of this study can provide a reference for further understanding of water vapor budget changes and abnormal precipitation events in South China.
South China is an important water vapor transport channel. Studying the water vapor budget in South China is essential for predicting precipitation processes in South China and its neighboring areas, and comprehending the impact of atmospheric circulation changes on weather and climate in China. Based on ERA5 data, the variation trend of water vapor budget and its correlation with precipitation in South China during the recent 40 years (1983-2022) are analyzed. The results show that water vapor in South China is mainly input through its the southern and western boundaries, and output through the northern and eastern boundaries, with the net budget being negative. The water vapor budget shows a declining trend, with a significant decrease in the output from the eastern boundary. In the four seasons, the input and output water vapor budget declines most obviously in spring. Water vapor enters into the South China Region mainly from the Indian Ocean and the Bay of Bengal in the southwest direction and western Pacific in the southwest direction. Water vapor in the middle and lower layers (700 hPa) is primarily transported from the Indian Ocean and the Bay of Bengal, while water vapor in the lower layer (925 hPa) mainly originates from western Pacific. In the recent 40 years, water vapor transport from the Indian Ocean and the Bay of Bengal and western Pacific has been weakening, causing the changes in water vapor transport from the direction of northeast to southwest in South China. Water vapor transport is positively correlated to precipitation in most areas of Guangxi and Guangdong, with correlation coefficient >0.6, of which the strengthening of southwestly water vapor transport is the key reason of precipitation. In addition, there is a trend of wetting in South China, with a 2.32% increase in precipitable water vapor (PWV) during the recent 40 years, which is the result of decrease in total water vapor outflow in the region than that of total inflow. The results of this study can provide a reference for further understanding of water vapor budget changes and abnormal precipitation events in South China.
2025, 51(7):803-816.
DOI: 10.7519/j.issn.1000-0526.2025.022402
Abstract:
Based on the minute precipitation observation data from Wuhan national meteorological stations since 1950s, the sliding accumulation method is used to identify short-duration heavy rainfall events, and the fuzzy identification method is used to determine the rain types of every single rainfall event. In addition, the spatio-temporal characteristics of short-duration heavy rainfall in Wuhan are systematically analyzed from the aspects of occurrence frequency, intensity and rain type, and the influence of urbanization on short-duration heavy rainfall is preliminarily explored. The results show that from 1954 to 2022, the short-duration heavy rainfall events in Wuhan show a small increasing trend, which suggests that the averaged annual frequency of heavy rainfall, annual average heavy precipitation, annual maximum 60-min heavy precipitation and annual maximum single heavy precipitation are 6.9 times, 289.9 mm, 98.0 mm and 282.2 mm, while the increasing rates are 0.3 times per 10 a, 16.7 mm per 10 a, 1.4 mm per 10 a and 0.9 mm per 10 a, respectively. Among them, the frequency and amount of annual heavy precipitation exhibit interdecadal characteristics, approximately presenting a “W” shape of “decrease-increase-decrease-increase”. The occurrence rate and contribution of heavy rainfall lasting for 60-120 min are the largest, being 41.6% and 32.2%, respectively. Heaviest rainfall in Wuhan mainly occurs from late June to mid-July, accounting for 33.6% of the whole year. The frequency of daily heavy rainfall is approximately unimodal, while the peak value occurs in 05:11 BT-05:40 BT, and the trough value occurs in 15:58 BT-16:47 BT. The average minute rainfall intensity is distributed in multi-peaks, with the main peak value appearing in 16:04 BT-17:34 BT, and the trough vlaue could be found in 07:53 BT-08:27 BT. The average minute rain intensity during daytime is greater than that at night, especially during 14:00 BT-20:00 BT. The average frequency of peaks and valleys per minute in spring is earlier than the annual average. In terms of individual rain patterns, the heavy rainfall at each station in Wuhan is dominated by the type Ⅰ and type Ⅳ rain patterns, while the heavy rainfall in 0-60 min is dominated by the type Ⅰ and type Ⅲ, and the heavy rainfall in more than 180 min is mainly type Ⅳ. The spatial variability of short-duration heavy rainfall in Wuhan area is relatively small, and the frequency, duration and precipitation of heavy rainfallin urban area are slightly higher than those in suburban area.
Based on the minute precipitation observation data from Wuhan national meteorological stations since 1950s, the sliding accumulation method is used to identify short-duration heavy rainfall events, and the fuzzy identification method is used to determine the rain types of every single rainfall event. In addition, the spatio-temporal characteristics of short-duration heavy rainfall in Wuhan are systematically analyzed from the aspects of occurrence frequency, intensity and rain type, and the influence of urbanization on short-duration heavy rainfall is preliminarily explored. The results show that from 1954 to 2022, the short-duration heavy rainfall events in Wuhan show a small increasing trend, which suggests that the averaged annual frequency of heavy rainfall, annual average heavy precipitation, annual maximum 60-min heavy precipitation and annual maximum single heavy precipitation are 6.9 times, 289.9 mm, 98.0 mm and 282.2 mm, while the increasing rates are 0.3 times per 10 a, 16.7 mm per 10 a, 1.4 mm per 10 a and 0.9 mm per 10 a, respectively. Among them, the frequency and amount of annual heavy precipitation exhibit interdecadal characteristics, approximately presenting a “W” shape of “decrease-increase-decrease-increase”. The occurrence rate and contribution of heavy rainfall lasting for 60-120 min are the largest, being 41.6% and 32.2%, respectively. Heaviest rainfall in Wuhan mainly occurs from late June to mid-July, accounting for 33.6% of the whole year. The frequency of daily heavy rainfall is approximately unimodal, while the peak value occurs in 05:11 BT-05:40 BT, and the trough value occurs in 15:58 BT-16:47 BT. The average minute rainfall intensity is distributed in multi-peaks, with the main peak value appearing in 16:04 BT-17:34 BT, and the trough vlaue could be found in 07:53 BT-08:27 BT. The average minute rain intensity during daytime is greater than that at night, especially during 14:00 BT-20:00 BT. The average frequency of peaks and valleys per minute in spring is earlier than the annual average. In terms of individual rain patterns, the heavy rainfall at each station in Wuhan is dominated by the type Ⅰ and type Ⅳ rain patterns, while the heavy rainfall in 0-60 min is dominated by the type Ⅰ and type Ⅲ, and the heavy rainfall in more than 180 min is mainly type Ⅳ. The spatial variability of short-duration heavy rainfall in Wuhan area is relatively small, and the frequency, duration and precipitation of heavy rainfallin urban area are slightly higher than those in suburban area.
2025, 51(7):817-829.
DOI: 10.7519/j.issn.1000-0526.2025.011502
Abstract:
To provide a reference for weather forecasting of major floods in the upper reaches of the Hanjiang River during autumn flood season, based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, we analyze the water regimen and rainfall characteristics, large-scale circulation characteristics, and causes for flood-causing rainstorm of major floods in the upper reaches of the Hanjiang River during autumn flood season since 2000. The results showed that the flood processes in the Hanjiang River Basin have gradually increased during autumn flood season since the 21st century. The flood-causing rainstorm center in autumn flood season is mainly located in the south and west of the upper reaches of the Hanjiang River, that is, the Micang Mountain and Daba Mountain in the south of the Hanjiang River Basin, the river valley in the upstream of the Ankang Reservoir, and the Danjiang River section at the southern foot of the Waifang Mountain and the westsouth slope of the Funiu Mountain. The peak of floods usually presents in the patterns of single peak, double peak or multiple peak. The duration of a single peak flood process is the shortest, while the duration of a multipeak flood process is the longest. The duration from the onset of maximum precipitation to the appearance of the flood peak is 43 h on average. When the initial inflow exceeds 4500 m3·s-1, the time required for the formation of the flood peak will be greatly shortened. From the perspective of large-scale circulation characteristics, the abnormal precipita-tion in the upper reaches of the Hanjiang River in autumn flood season is closely correlated to the strong blocking system in the mid-high latitudes over the Eurasia, the stronger and westward Western Pacific subtropical high, the northward South Asia high and subtropical westerly jet flow. The high-level divergence large-value area corresponds to the upper reaches of the Hanjiang River. The vertical motion from low to high levels is enhanced, which is conducive to the occurrence of flood-causing rainstorm. The water vapor transported northward from the Arabian Sea through the Indian Peninsula and the southern South China Sea and westward from the Western Pacific in autumn flood season flood year in the upper reaches of the Hanjiang River has increased abnormally, providing an unusually sufficient water vapor supply for the occurrence of flood-causing rainstorm.
To provide a reference for weather forecasting of major floods in the upper reaches of the Hanjiang River during autumn flood season, based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, we analyze the water regimen and rainfall characteristics, large-scale circulation characteristics, and causes for flood-causing rainstorm of major floods in the upper reaches of the Hanjiang River during autumn flood season since 2000. The results showed that the flood processes in the Hanjiang River Basin have gradually increased during autumn flood season since the 21st century. The flood-causing rainstorm center in autumn flood season is mainly located in the south and west of the upper reaches of the Hanjiang River, that is, the Micang Mountain and Daba Mountain in the south of the Hanjiang River Basin, the river valley in the upstream of the Ankang Reservoir, and the Danjiang River section at the southern foot of the Waifang Mountain and the westsouth slope of the Funiu Mountain. The peak of floods usually presents in the patterns of single peak, double peak or multiple peak. The duration of a single peak flood process is the shortest, while the duration of a multipeak flood process is the longest. The duration from the onset of maximum precipitation to the appearance of the flood peak is 43 h on average. When the initial inflow exceeds 4500 m3·s-1, the time required for the formation of the flood peak will be greatly shortened. From the perspective of large-scale circulation characteristics, the abnormal precipita-tion in the upper reaches of the Hanjiang River in autumn flood season is closely correlated to the strong blocking system in the mid-high latitudes over the Eurasia, the stronger and westward Western Pacific subtropical high, the northward South Asia high and subtropical westerly jet flow. The high-level divergence large-value area corresponds to the upper reaches of the Hanjiang River. The vertical motion from low to high levels is enhanced, which is conducive to the occurrence of flood-causing rainstorm. The water vapor transported northward from the Arabian Sea through the Indian Peninsula and the southern South China Sea and westward from the Western Pacific in autumn flood season flood year in the upper reaches of the Hanjiang River has increased abnormally, providing an unusually sufficient water vapor supply for the occurrence of flood-causing rainstorm.
2025, 51(7):830-839.
DOI: 10.7519/j.issn.1000-0526.2025.041501
Abstract:
Based on ERA5 hourly reanalysis data of atmospheric circulation field with horizontal resolution of 0.25°×0.25°, geopotential height data and temperature, the northeast cold vortex process and its climate change characteristics from 1979 to 2023 are analyzed. The results reveal that there are more northeast cold vortexes in the early 1990s and mid-2000s, and relatively fewer in the 2010s. The frequency of northeast cold vortex shows higher in the warm season than in the cold season, with the highest in June and the lowest in March. Its average duration is 4 days, with the shortest duration in April and the longest duration in January. The northeast cold vortex is mostly generated in the range of 45°-60°N, 100°-120°E and dies out within 40°-55°N near 140°E. The center of the northeast cold vortex is mainly concentrated within 45°-55°N and 115°-135°E. The northeast cold vortex mainly moves towards the east and southeast. To the east of 120°E, the average intensity of the cold vortex is stronger and weaker to the west. The intensity distribution of the northeast cold vortex within the year is stronger in the cold season than in the warm season. The intensity difference between the grids in the analysis area is the largest in March, and the smallest in June. The annual average intensity and circulation of northeast cold vortex show a significant weakening trend from 1979 to 2023. There is a significant negative correlation between the intensity of the northeast cold vortex and the temperature in most months in Northeast China, but a significant positive correlation with precipitation in April and June.
Based on ERA5 hourly reanalysis data of atmospheric circulation field with horizontal resolution of 0.25°×0.25°, geopotential height data and temperature, the northeast cold vortex process and its climate change characteristics from 1979 to 2023 are analyzed. The results reveal that there are more northeast cold vortexes in the early 1990s and mid-2000s, and relatively fewer in the 2010s. The frequency of northeast cold vortex shows higher in the warm season than in the cold season, with the highest in June and the lowest in March. Its average duration is 4 days, with the shortest duration in April and the longest duration in January. The northeast cold vortex is mostly generated in the range of 45°-60°N, 100°-120°E and dies out within 40°-55°N near 140°E. The center of the northeast cold vortex is mainly concentrated within 45°-55°N and 115°-135°E. The northeast cold vortex mainly moves towards the east and southeast. To the east of 120°E, the average intensity of the cold vortex is stronger and weaker to the west. The intensity distribution of the northeast cold vortex within the year is stronger in the cold season than in the warm season. The intensity difference between the grids in the analysis area is the largest in March, and the smallest in June. The annual average intensity and circulation of northeast cold vortex show a significant weakening trend from 1979 to 2023. There is a significant negative correlation between the intensity of the northeast cold vortex and the temperature in most months in Northeast China, but a significant positive correlation with precipitation in April and June.
2025, 51(7):840-851.
DOI: 10.7519/j.issn.1000-0526.2024.123102
Abstract:
Constructing a quantitative index to characterize the intensity of low-temperature freezing injury of winter wheat and revealing its spatio-temporal variation characteristics is crucial for scientific prevention of low-temperature freezing injury of winter wheat. Based on the winter daily meteorological observation data in Jiangsu Province from 1972 to 2022, disaster data of freezing injury of winter wheat from 2010 to 2022, and yield data of historical extreme freezing injury years, this paper determines the impact weights of disaster-causing factors on different types of freezing injury, and establishes three main types of freezing injury indices, including low-temperature freezing injury (last November to March), freezing injury during overwintering period (late December to mid February), and freezing injury during regreening-jointing period (late February to March). Multiple mathematical statistical methods such as Mann-Kendall mutation test and k-means clustering are used to conduct spatio-temporal analysis and evaluation of low-temperature freezing injury of winter wheat. Based on the ranking of freezing injury intensity during overwintering period and regreening-jointing period, two types of freezing injuries are classified into three levels, which are mild, moderate and severe. The results show that there is a significant difference in the intensity indices of low-temperature freezing injury between the north and the south of Jiangsu Province. They can be divided into high-risk zone (Xuzhou, Lianyungang, Suqian, Huai’an and Yancheng), medium-risk zone (Nanjing, Yangzhou, Taizhou and Nantong), and low-risk zone (Zhenjiang, Changzhou, Suzhou and Wuxi). Over the past 51 years, the intensity index of low-temperature freezing injury of winter wheat experienced a sudden decline in 1989 in Jiangsu Province. The severe freezing injury during overwintering period and regreening-jointing period both jumped from a relatively more injury period to a relatively fewer injury period in the late 1980s. Although the frequency of freezing injury during the development period of winter wheat has shown a decreasing trend, the intensity of extreme freezing injury has been increasing, and even the freezing injury index in some areas exceeded the historical record of 1977 in the 21st century.
Constructing a quantitative index to characterize the intensity of low-temperature freezing injury of winter wheat and revealing its spatio-temporal variation characteristics is crucial for scientific prevention of low-temperature freezing injury of winter wheat. Based on the winter daily meteorological observation data in Jiangsu Province from 1972 to 2022, disaster data of freezing injury of winter wheat from 2010 to 2022, and yield data of historical extreme freezing injury years, this paper determines the impact weights of disaster-causing factors on different types of freezing injury, and establishes three main types of freezing injury indices, including low-temperature freezing injury (last November to March), freezing injury during overwintering period (late December to mid February), and freezing injury during regreening-jointing period (late February to March). Multiple mathematical statistical methods such as Mann-Kendall mutation test and k-means clustering are used to conduct spatio-temporal analysis and evaluation of low-temperature freezing injury of winter wheat. Based on the ranking of freezing injury intensity during overwintering period and regreening-jointing period, two types of freezing injuries are classified into three levels, which are mild, moderate and severe. The results show that there is a significant difference in the intensity indices of low-temperature freezing injury between the north and the south of Jiangsu Province. They can be divided into high-risk zone (Xuzhou, Lianyungang, Suqian, Huai’an and Yancheng), medium-risk zone (Nanjing, Yangzhou, Taizhou and Nantong), and low-risk zone (Zhenjiang, Changzhou, Suzhou and Wuxi). Over the past 51 years, the intensity index of low-temperature freezing injury of winter wheat experienced a sudden decline in 1989 in Jiangsu Province. The severe freezing injury during overwintering period and regreening-jointing period both jumped from a relatively more injury period to a relatively fewer injury period in the late 1980s. Although the frequency of freezing injury during the development period of winter wheat has shown a decreasing trend, the intensity of extreme freezing injury has been increasing, and even the freezing injury index in some areas exceeded the historical record of 1977 in the 21st century.
2025, 51(7):852-864.
DOI: 10.7519/j.issn.1000-0526.2025.010801
Abstract:
Liquid water content (LWC), median volume diameter (MVD), outside air temperature and other meteorological conditions are important meteorological factors affecting the intensity of aircraft icing, and are also the basic condition for measuring and evaluating whether the aircraft natural icing certification flight test meets the natiural icing certification flight test standard. The meteorological conditions of a domestic large passenger aircraft natural icing test flight on 22 January 2022 are analyzed based on multi-source meteorological data. The results show that the high-altitude weather background of this natural icing certification flight test was a latitudinal fluctuating airflow, cooperated with the cold air inversion near the surface, forcing the southwest warm and humid airflow in the middle and lower layers of the troposphere to lift northward, and forming a wide range of non-precipitation layered cloud system. The height of the cloud top in the test area developed from 3.0 km to 4.6 km, and an inversion layer existed in 1.3-3.5 km, with the lowest temperature at the cloud top being -14℃, no precipitation in the cloud, and the radar basic reflectivity＜15 dBz. The ambient temperature of the two times of fights penetrating the cloud and the standby flight in the cloud for 45 min hovering flights was from -10 to -7℃, with the relative humidity＞80%, and the scattering of water vapor flux＜-2.73×10-7 g·s-1·hPa-1·cm-2. This provided ideal temperature and water vapor conditions for the natural icing test flights, and a weak updraft of -0.2 Pa·s-1 in the middle and upper part of the cloud layer contributed to the growth of the supercooled cloud droplets. The DMT sounding data show that the supercooled cloud is inhomogeneous both vertically and horizontally, and that the supercooled cloud droplets were dominant inside the cloud, where the mean value of LWC was 0.23-0.27 g·m-3, and the mean value of MVD was 15.82-15.93 μm. So there are aircraft natural icing meteorological conditions in winter under the influence of the “inversion + inversion trough” weather system, which is conducive to carrying out aircraft natural icing certification tests in Shaanxi.
Liquid water content (LWC), median volume diameter (MVD), outside air temperature and other meteorological conditions are important meteorological factors affecting the intensity of aircraft icing, and are also the basic condition for measuring and evaluating whether the aircraft natural icing certification flight test meets the natiural icing certification flight test standard. The meteorological conditions of a domestic large passenger aircraft natural icing test flight on 22 January 2022 are analyzed based on multi-source meteorological data. The results show that the high-altitude weather background of this natural icing certification flight test was a latitudinal fluctuating airflow, cooperated with the cold air inversion near the surface, forcing the southwest warm and humid airflow in the middle and lower layers of the troposphere to lift northward, and forming a wide range of non-precipitation layered cloud system. The height of the cloud top in the test area developed from 3.0 km to 4.6 km, and an inversion layer existed in 1.3-3.5 km, with the lowest temperature at the cloud top being -14℃, no precipitation in the cloud, and the radar basic reflectivity＜15 dBz. The ambient temperature of the two times of fights penetrating the cloud and the standby flight in the cloud for 45 min hovering flights was from -10 to -7℃, with the relative humidity＞80%, and the scattering of water vapor flux＜-2.73×10-7 g·s-1·hPa-1·cm-2. This provided ideal temperature and water vapor conditions for the natural icing test flights, and a weak updraft of -0.2 Pa·s-1 in the middle and upper part of the cloud layer contributed to the growth of the supercooled cloud droplets. The DMT sounding data show that the supercooled cloud is inhomogeneous both vertically and horizontally, and that the supercooled cloud droplets were dominant inside the cloud, where the mean value of LWC was 0.23-0.27 g·m-3, and the mean value of MVD was 15.82-15.93 μm. So there are aircraft natural icing meteorological conditions in winter under the influence of the “inversion + inversion trough” weather system, which is conducive to carrying out aircraft natural icing certification tests in Shaanxi.
2025, 51(7):865-875.
DOI: 10.7519/j.issn.1000-0526.2025.022101
Abstract:
On 28 December 2022, multiple vehicle collisions occurred on the Zhengxin Yellow River Bridge due to heavy fog. Based on ERA5 reanalysis and surface observation data, the method of disturbance-based synoptic analysis is used to diagnose and analyze the heavy fog episode. The results show that the heavy fog weather had the characteristics of strong local suddenness, low visibility, and significant nighttime cooling. The low visibility caused by heavy fog and the ice and slippery bridge deck caused by high humidity and low temperature were the meteorological reasons for the vehicle rear-end collision accidents. The synoptic conditions were stable, with weak cold air at the bottom and warm ridges in the southwest transport of warm and humid airflow into the foggy area, and the circulation pattern was favorable for the generation of fog. The water vapor flux near the bridge was high, and there existed weak water vapor convergence, shallow inversion layer and strong radiation cooling effect, which provided favorable dynamic, water vapor, and thermal conditions for the occurrence and persistence of radiation fog. The disturbance signals of wind speed, relative humidity, temperature and specific humidity can better reflect the predictable signals of heavy fog compared to the corresponding disturbance signals. The comprehensive analysis of multiple disturbance factors can help determine the dissipation time of fog.
On 28 December 2022, multiple vehicle collisions occurred on the Zhengxin Yellow River Bridge due to heavy fog. Based on ERA5 reanalysis and surface observation data, the method of disturbance-based synoptic analysis is used to diagnose and analyze the heavy fog episode. The results show that the heavy fog weather had the characteristics of strong local suddenness, low visibility, and significant nighttime cooling. The low visibility caused by heavy fog and the ice and slippery bridge deck caused by high humidity and low temperature were the meteorological reasons for the vehicle rear-end collision accidents. The synoptic conditions were stable, with weak cold air at the bottom and warm ridges in the southwest transport of warm and humid airflow into the foggy area, and the circulation pattern was favorable for the generation of fog. The water vapor flux near the bridge was high, and there existed weak water vapor convergence, shallow inversion layer and strong radiation cooling effect, which provided favorable dynamic, water vapor, and thermal conditions for the occurrence and persistence of radiation fog. The disturbance signals of wind speed, relative humidity, temperature and specific humidity can better reflect the predictable signals of heavy fog compared to the corresponding disturbance signals. The comprehensive analysis of multiple disturbance factors can help determine the dissipation time of fog.
2025, 51(7):876-890.
DOI: 10.7519/j.issn.1000-0526.2025.060601
Abstract:
In the winter of 2024/2025, the mean temperature in China was 0.4℃ higher than normal with significant intra-seasonal variations. Average precipitation was 41.1% lower than normal, and the regions south of the Yangtze River experienced persistently less precipitation. Atmospheric circulation patterns in the mid-to-high latitudes over Eurasia have shown staged differences in this winter. In December 2024, the Arctic Oscillation was in a negative phase and the East Asian trough and Siberian high were stronger than usual. All the three got weakened in January 2025 and then strengthened again in February. Especially in February, the negative phase of the Arctic Oscillation reached the strongest stage of this winter while the activity of Eurasian blocking high was significantly enhanced. These factors collectively triggered an obvious shift in the temperature of China from warmer to colder conditions. In the 2024/2025 winter, the low-latitude atmosphere responded significantly to the La Nina-type sea surface temperature anomalies in the equatorial central-eastern Pacific. Persistent cyclonic circulation anomalies dominated the lower troposphere from the Philippines to the South China Sea, while the regions south of the Yangtze River in China remained consistently influenced by northerly wind anomalies. Coupled with persistently weak activity of the India-Burma trough, the influences of multiple circulation conditions led to sustained moisture transport deficits and significantly reduced precipitation in eastern China, particularly in the southern part.
In the winter of 2024/2025, the mean temperature in China was 0.4℃ higher than normal with significant intra-seasonal variations. Average precipitation was 41.1% lower than normal, and the regions south of the Yangtze River experienced persistently less precipitation. Atmospheric circulation patterns in the mid-to-high latitudes over Eurasia have shown staged differences in this winter. In December 2024, the Arctic Oscillation was in a negative phase and the East Asian trough and Siberian high were stronger than usual. All the three got weakened in January 2025 and then strengthened again in February. Especially in February, the negative phase of the Arctic Oscillation reached the strongest stage of this winter while the activity of Eurasian blocking high was significantly enhanced. These factors collectively triggered an obvious shift in the temperature of China from warmer to colder conditions. In the 2024/2025 winter, the low-latitude atmosphere responded significantly to the La Nina-type sea surface temperature anomalies in the equatorial central-eastern Pacific. Persistent cyclonic circulation anomalies dominated the lower troposphere from the Philippines to the South China Sea, while the regions south of the Yangtze River in China remained consistently influenced by northerly wind anomalies. Coupled with persistently weak activity of the India-Burma trough, the influences of multiple circulation conditions led to sustained moisture transport deficits and significantly reduced precipitation in eastern China, particularly in the southern part.
2025, 51(7):891-900.
DOI: 10.7519/j.issn.1000-0526.2025.063001
Abstract:
In April 2025, the Northern Hemisphere polar vortex exhibited a monopole with an eccentric distribution and was stronger than normal. Over the Eurasian mid-to-high latitudes, the circulation pattern featured a pattern of “two troughs and one ridge”. The ridge between the East European trough and the East Asian trough was broad and flat. The national average temperature across the whole China was 13℃, which is 1.5℃ higher than the climatological average (11.5℃) in the same period. The national average precipitation was 38.9 mm, 11% less than the climatological average (43.6 mm). The main precipitation areas were located in Jiangnan and the northern parts of South China. The precipitation of Eastern Inner Mongolia and Northeast China was above the normal level. During this month, there were five major sand-dust processes, two cold air, three heavy rainfall processes, and four severe convective weather processes. Notably, the strong sandstorm process from 10 to 14 April was characterized by its long duration, high intensity and extensive dust coverage. This event was also accompanied by widespread strong winds and a significant drop in temperature.
In April 2025, the Northern Hemisphere polar vortex exhibited a monopole with an eccentric distribution and was stronger than normal. Over the Eurasian mid-to-high latitudes, the circulation pattern featured a pattern of “two troughs and one ridge”. The ridge between the East European trough and the East Asian trough was broad and flat. The national average temperature across the whole China was 13℃, which is 1.5℃ higher than the climatological average (11.5℃) in the same period. The national average precipitation was 38.9 mm, 11% less than the climatological average (43.6 mm). The main precipitation areas were located in Jiangnan and the northern parts of South China. The precipitation of Eastern Inner Mongolia and Northeast China was above the normal level. During this month, there were five major sand-dust processes, two cold air, three heavy rainfall processes, and four severe convective weather processes. Notably, the strong sandstorm process from 10 to 14 April was characterized by its long duration, high intensity and extensive dust coverage. This event was also accompanied by widespread strong winds and a significant drop in temperature.
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ISSN:1000-0526 CN:11-2282/P