Volume 51,Issue 1,2023 Table of Contents
2023, 51(1):1-13.
DOI: 10.19517/j.1671-6345.20210301
Abstract:
The reliability of FY-4A temperature and humidity profiles are verified by using conventional sounding data and ERA5 data in Guangxi Province during the strong convection processes from February 2019 to February 2020. The results show that: (1) The FY-4A temperature and humidity profiles have lower deviation for the clear sky. Compared with radiosonde data, the root mean squared error (RMSE) of FY-4A temperature with quality control 0 and 1 data ranges from 1.04 ℃ to 4.16 ℃, and the overall RMSE is 2.61 ℃. The inversion accuracy of temperature is better in 850-700 hPa, 600-500 hPa and 250 hPa, all of which have a RMSE less than 2 ℃. The different distribution of temperature profiles between FY-4A and ERA5 is similar to the above. The RMSE ranges from 1.01 ℃ to 4.15 ℃, and the overall RMSE is 2.19 ℃. RMSE is less than 2 ℃ at 925-400 hPa and 250 hPa. (2) The overall RMSE of FY-4A humidity profile is 61.06% compared to radiosonde data under the clear sky, and there is a relatively small error in 900-700 hPa with an averaging RMSE of about 20.51%. The error reaches the maximum near 500 hPa, which may be related to the sudden change of water content in the vertical direction caused by dry air intrusion. In addition, the errors of the lower troposphere are generally smaller than those of the upper troposphere. (3) The reconstructed Tlnp diagram in the strong convection case can restore the temperature and humidity structure characteristics of the upper and lower layers of the atmosphere to a certain extent. However, there is still deviation in the quantitative estimation of stratification stability and unstable energy. The temperature data can better reflect the activity characteristics of cold and warm air after quality control, which provide a prompting effect on the monitoring of strong convective potential. The available high-quality samples are reduced when affected by the cloud, which needs to be corrected by multi-source data in the application.
The reliability of FY-4A temperature and humidity profiles are verified by using conventional sounding data and ERA5 data in Guangxi Province during the strong convection processes from February 2019 to February 2020. The results show that: (1) The FY-4A temperature and humidity profiles have lower deviation for the clear sky. Compared with radiosonde data, the root mean squared error (RMSE) of FY-4A temperature with quality control 0 and 1 data ranges from 1.04 ℃ to 4.16 ℃, and the overall RMSE is 2.61 ℃. The inversion accuracy of temperature is better in 850-700 hPa, 600-500 hPa and 250 hPa, all of which have a RMSE less than 2 ℃. The different distribution of temperature profiles between FY-4A and ERA5 is similar to the above. The RMSE ranges from 1.01 ℃ to 4.15 ℃, and the overall RMSE is 2.19 ℃. RMSE is less than 2 ℃ at 925-400 hPa and 250 hPa. (2) The overall RMSE of FY-4A humidity profile is 61.06% compared to radiosonde data under the clear sky, and there is a relatively small error in 900-700 hPa with an averaging RMSE of about 20.51%. The error reaches the maximum near 500 hPa, which may be related to the sudden change of water content in the vertical direction caused by dry air intrusion. In addition, the errors of the lower troposphere are generally smaller than those of the upper troposphere. (3) The reconstructed Tlnp diagram in the strong convection case can restore the temperature and humidity structure characteristics of the upper and lower layers of the atmosphere to a certain extent. However, there is still deviation in the quantitative estimation of stratification stability and unstable energy. The temperature data can better reflect the activity characteristics of cold and warm air after quality control, which provide a prompting effect on the monitoring of strong convective potential. The available high-quality samples are reduced when affected by the cloud, which needs to be corrected by multi-source data in the application.
2023, 51(1):14-21.
DOI: 10.19517/j.1671-6345.20220120
Abstract:
In order to better exert the monitoring and early warning application potential of satellitetoground lightning detection data in the Mesoscale Convective System (MCS), this study takes an MCS in Shandong on June 27, 2018, as a case, using the cloud top temperature, cooling rate, the reflectivity from radar and the satellite-to-ground lightning data from FY-4A Lightning Mapping Imager (LMI) and Advanced TOA and Direction system (ADTD) to analyze the lightning distribution characteristics and its relationship with the evolution of convection. The results show a good consistence of the satellite-to-ground lightning data. The lighting of LMI was further located in front of the convective cloud and had a high agreement with the precipitation region. In the early development stage of MSC, LMI detected lightning earlier than ADTD, and the lightning was located in the centre and the front side of the radar echo. The vertical section of the echo showed a forward tilting, which was a good indicator of the movement and evolution trend of convection. Thus, the location of the lightning from LMI could be used to assist in the forecast of strong convection areas. In the mature stage, the frequency of satellite-to-ground lightning increased, and the proportion of positive ground lightning was relatively large. Hail disasters occurred in many places in Shandong Province during this period. The LMI mostly appeared in the weak or no-echo area in front of the moving direction of the convective system, while the ADTD lightning was closer to the centre position of the echo. During the merging stage, some of the LMI lightning was located at the backside of the front, strong echo area corresponding to the strong echo area.
In order to better exert the monitoring and early warning application potential of satellitetoground lightning detection data in the Mesoscale Convective System (MCS), this study takes an MCS in Shandong on June 27, 2018, as a case, using the cloud top temperature, cooling rate, the reflectivity from radar and the satellite-to-ground lightning data from FY-4A Lightning Mapping Imager (LMI) and Advanced TOA and Direction system (ADTD) to analyze the lightning distribution characteristics and its relationship with the evolution of convection. The results show a good consistence of the satellite-to-ground lightning data. The lighting of LMI was further located in front of the convective cloud and had a high agreement with the precipitation region. In the early development stage of MSC, LMI detected lightning earlier than ADTD, and the lightning was located in the centre and the front side of the radar echo. The vertical section of the echo showed a forward tilting, which was a good indicator of the movement and evolution trend of convection. Thus, the location of the lightning from LMI could be used to assist in the forecast of strong convection areas. In the mature stage, the frequency of satellite-to-ground lightning increased, and the proportion of positive ground lightning was relatively large. Hail disasters occurred in many places in Shandong Province during this period. The LMI mostly appeared in the weak or no-echo area in front of the moving direction of the convective system, while the ADTD lightning was closer to the centre position of the echo. During the merging stage, some of the LMI lightning was located at the backside of the front, strong echo area corresponding to the strong echo area.
2023, 51(1):22-30.
DOI: 10.19517/j.1671-6345.20220134
Abstract:
With the development of modern space technology, accurate point coordinates have been widely used since the official opening of CGCS2000 in China. High-resolution weather radar, with a range bin size of usually less than 100 meters, needs more precise coordinates to represent meteorological echo positions in today’s operational applications. For the availability of radar echo’s accurate coordinates in CGCS2000, a series of mathematical relationships have been established between the Earth ellipsoid and radar RPS (a reference positioning sphere of radar) and have been utilised to compute typical coordinates associated with radar echoes, such as geodetic coordinates, geocentric coordinates, radar reference coordinates and radar observation coordinates. The error analysis of the earth spherical approximation method shows that horizontal deviation is the main error expression and correlates with radar geographic position and echo’s radar observation coordinates. The deviation level of high-or-low-latitude radar is greater than that of middle-latitude radar. The maximum deviation increases with the radar detection range. The ratio of the maximum deviation to detection range from 50 km to 400 km is between 2‰ and 5‰. The error influences can be ignored in general but not in some high-precision computations.
With the development of modern space technology, accurate point coordinates have been widely used since the official opening of CGCS2000 in China. High-resolution weather radar, with a range bin size of usually less than 100 meters, needs more precise coordinates to represent meteorological echo positions in today’s operational applications. For the availability of radar echo’s accurate coordinates in CGCS2000, a series of mathematical relationships have been established between the Earth ellipsoid and radar RPS (a reference positioning sphere of radar) and have been utilised to compute typical coordinates associated with radar echoes, such as geodetic coordinates, geocentric coordinates, radar reference coordinates and radar observation coordinates. The error analysis of the earth spherical approximation method shows that horizontal deviation is the main error expression and correlates with radar geographic position and echo’s radar observation coordinates. The deviation level of high-or-low-latitude radar is greater than that of middle-latitude radar. The maximum deviation increases with the radar detection range. The ratio of the maximum deviation to detection range from 50 km to 400 km is between 2‰ and 5‰. The error influences can be ignored in general but not in some high-precision computations.
2023, 51(1):31-39.
DOI: 10.19517/j.1671-6345.20210493
Abstract:
In recent years, meteorological and climate services have increased their requirements for foreign data types and timeliness. An international meteorological communication data collection and management system based on process control is designed and implemented to solve the collection and distribution pressure and management problems of a large amount of data. The system applies the technology of Logstash, Inotify and Kibana, supports a variety of communication protocols, expands the network crawler function of Scrapy, and achieves the fast and efficient collection and integration management of a large amount of data through process control and task scheduling, effectively improving the data parallel processing ability and scalability. And the whole process of monitoring is designed to ensure data timeliness. The system has been online to provide services, providing operational/scientific research users with more than 300 kinds of global observation data, foreign satellite data and numerical prediction products; the daily data collection is about 2 TB.
In recent years, meteorological and climate services have increased their requirements for foreign data types and timeliness. An international meteorological communication data collection and management system based on process control is designed and implemented to solve the collection and distribution pressure and management problems of a large amount of data. The system applies the technology of Logstash, Inotify and Kibana, supports a variety of communication protocols, expands the network crawler function of Scrapy, and achieves the fast and efficient collection and integration management of a large amount of data through process control and task scheduling, effectively improving the data parallel processing ability and scalability. And the whole process of monitoring is designed to ensure data timeliness. The system has been online to provide services, providing operational/scientific research users with more than 300 kinds of global observation data, foreign satellite data and numerical prediction products; the daily data collection is about 2 TB.
2023, 51(1):40-48.
DOI: 10.19517/j.1671-6345.20210465
Abstract:
In order to solve the shortcomings of the meteorological weather forecast video conference system in free interaction, application scenarios and automatic control, a new generation of video conference system is designed and constructed. Based on cloud computing and virtualization technology, the system has built a cloud video conference platform for private cloud deployment, which makes up for the shortcomings of weather conference in Internet access. It expands the application of weather conference in official business trips, cross-departmental linkage and other scenarios. At the same time, by applying distributed technology to the system’s main control centre, the large capacity signal interaction and transmission based on IP encoding and decoding is realized. Compared with the original system, the interaction ability is improved by more than 15 times. The introduction of automatic conference control technology improves conference management and scheduling ability and significantly reduces operational complexity. Since the system was officially launched in March 2019, it has played a huge role in the service guarantee of major events such as the 70th anniversary of the National Day and in the service of meteorological departments in combating COVID-19.
In order to solve the shortcomings of the meteorological weather forecast video conference system in free interaction, application scenarios and automatic control, a new generation of video conference system is designed and constructed. Based on cloud computing and virtualization technology, the system has built a cloud video conference platform for private cloud deployment, which makes up for the shortcomings of weather conference in Internet access. It expands the application of weather conference in official business trips, cross-departmental linkage and other scenarios. At the same time, by applying distributed technology to the system’s main control centre, the large capacity signal interaction and transmission based on IP encoding and decoding is realized. Compared with the original system, the interaction ability is improved by more than 15 times. The introduction of automatic conference control technology improves conference management and scheduling ability and significantly reduces operational complexity. Since the system was officially launched in March 2019, it has played a huge role in the service guarantee of major events such as the 70th anniversary of the National Day and in the service of meteorological departments in combating COVID-19.
2023, 51(1):49-55.
DOI: 10.19517/j.1671-6345.20220045
Abstract:
The Integrated Operation and Control System (IOCS) is an important system of the polar-orbiting meteorological satellite ground application system. One of its main tasks is to plan the receiving tasks for multisatellite ground stations to ensure the complete acquisition of global data. When an antenna of a satellite ground station is abnormal or unavailable, if the data is still received according to the original task plan, it will directly lead to the incompleteness of global data. Therefore, it is necessary to research the antenna state prediction and its task replanning technology so as to timely discover and handle the antenna anomalies of the satellite ground station, reduce the risk of continuous multiorbit data receiving failure, and finally achieve the goal of improving the success rate of polar-orbiting meteorological satellites’ data receiving. In this paper, an antenna state prediction method for the satellite ground station based on statistical analysis is designed, and the task replanning method with minimum change to subsequent system operation, easy implementation and re-checkable results is studied.
The Integrated Operation and Control System (IOCS) is an important system of the polar-orbiting meteorological satellite ground application system. One of its main tasks is to plan the receiving tasks for multisatellite ground stations to ensure the complete acquisition of global data. When an antenna of a satellite ground station is abnormal or unavailable, if the data is still received according to the original task plan, it will directly lead to the incompleteness of global data. Therefore, it is necessary to research the antenna state prediction and its task replanning technology so as to timely discover and handle the antenna anomalies of the satellite ground station, reduce the risk of continuous multiorbit data receiving failure, and finally achieve the goal of improving the success rate of polar-orbiting meteorological satellites’ data receiving. In this paper, an antenna state prediction method for the satellite ground station based on statistical analysis is designed, and the task replanning method with minimum change to subsequent system operation, easy implementation and re-checkable results is studied.
2023, 51(1):56-65.
DOI: 10.19517/j.1671-6345.20220037
Abstract:
Based on the routine meteorological observation data at 2400 weather stations in China from 1961 to 2021, the basic summary of climate and major meteorological disasters in China in the autumn of 2021 is comprehensively analyzed according to “Regulations on Monitoring and Evaluation of Regional Important Processes” issued by the China Meteorological Administration in 2019. The results are as follows: (1) The climate condition in China in the autumn of 2021 was generally worse than normal; the average temperature was higher than that in the same period of normal years, and the average precipitation was more than that in the same period of normal years. The less landing typhoons and the cumulative effects of the heavy rain process in the affected area were significant, with the same as the cold air process, which caused the impact of rain, snow and freezing disasters in the north to be significantly higher than that in the south. (2) In the autumn of 2021, the meteorological disasters were complex and severe in China, and the multitype extreme weather and climate events, mainly including rainstorms and floods, high-temperature and droughts, low-temperature freezing rain and snow disasters, occurred frequently, which had significant phased and regional characteristics. The number of extremely heavy rainfall processes was 4.2 more than that in the same period in normal years. There were severe autumn floods in northern China, with heavy flooding in Shanxi, Shaanxi, etc. The number of regional high-temperature processes was 2.4 more than that in the same period of the year. The regional characteristics of the high-temperature process were significant, leading to Jiangnan and southern China witnessing the compound development of high temperature and droughts. Seven cold air processes occurred in China during the autumn, three of which were cold wave processes, 1.2 times more than the same period in normal years. The cumulative effects of the affected regions were significant, resulting in heavy snow in the three northeastern provinces and parts of Inner Mongolia.
Based on the routine meteorological observation data at 2400 weather stations in China from 1961 to 2021, the basic summary of climate and major meteorological disasters in China in the autumn of 2021 is comprehensively analyzed according to “Regulations on Monitoring and Evaluation of Regional Important Processes” issued by the China Meteorological Administration in 2019. The results are as follows: (1) The climate condition in China in the autumn of 2021 was generally worse than normal; the average temperature was higher than that in the same period of normal years, and the average precipitation was more than that in the same period of normal years. The less landing typhoons and the cumulative effects of the heavy rain process in the affected area were significant, with the same as the cold air process, which caused the impact of rain, snow and freezing disasters in the north to be significantly higher than that in the south. (2) In the autumn of 2021, the meteorological disasters were complex and severe in China, and the multitype extreme weather and climate events, mainly including rainstorms and floods, high-temperature and droughts, low-temperature freezing rain and snow disasters, occurred frequently, which had significant phased and regional characteristics. The number of extremely heavy rainfall processes was 4.2 more than that in the same period in normal years. There were severe autumn floods in northern China, with heavy flooding in Shanxi, Shaanxi, etc. The number of regional high-temperature processes was 2.4 more than that in the same period of the year. The regional characteristics of the high-temperature process were significant, leading to Jiangnan and southern China witnessing the compound development of high temperature and droughts. Seven cold air processes occurred in China during the autumn, three of which were cold wave processes, 1.2 times more than the same period in normal years. The cumulative effects of the affected regions were significant, resulting in heavy snow in the three northeastern provinces and parts of Inner Mongolia.
2023, 51(1):66-74.
DOI: 10.19517/j.1671-6345.20210428
Abstract:
Global climate warming and rapid urbanization have caused significant increases in the frequency, intensity, and duration of urban summer high temperature and heat waves. However, the knowledge of long-term characteristics, affecting degree, and driving mechanism of summer high temperatures on urban heat islands in highly populated megalopolises still need to be discovered. Beijing is the centre of the Beijing-Tianjin-Hebei metropolitan area and has experienced rapid urbanization in the past few decades. This study aims to elucidate the long-term trends of summer (May-August) high temperatures and explore the affecting mechanism of summer high temperatures on urban heat islands based on 43 years (1978-2020) daily meteorological observation data from the urban station (Beijing Station) and rural station (Miyun and Yanqing Stations). In the past four decades, the summer high-temperature days, intensity, and the yearly extreme maximal air temperature have shown significant increasing trends. Correspondingly, the initial time of summer high-temperature day was markedly advanced, and the end time of summer high-temperature day was significantly delayed. The urban heat island intensity of maximal air temperature significantly decreased, but the urban heat island intensities of mean and minimal air temperature slightly decreased during the summer high-temperature period from 1978 to 2020. The urban heat island intensities of maximal, mean and minimal air temperature during the summer high-temperature period were 0.73 ℃, 1.61 ℃, and 2.40 ℃, which were significantly higher than 0.09 ℃, 0.80 ℃, and 140 ℃ during the summer non-high temperature period from 1978 to 2020. The urban heat island intensity was significantly aggravated (more than 0.6 ℃) during the period with high-temperature compared to the period without high temperature, indicating that the urban heat island effect was amplified by summer high temperature. It is projected that summer high temperatures would become more frequent, and urban heat islands in Beijing would markedly increase under the background of future climate warming and rapid urbanization. These findings underline the serious heatrelated health risks facing urban residents.
Global climate warming and rapid urbanization have caused significant increases in the frequency, intensity, and duration of urban summer high temperature and heat waves. However, the knowledge of long-term characteristics, affecting degree, and driving mechanism of summer high temperatures on urban heat islands in highly populated megalopolises still need to be discovered. Beijing is the centre of the Beijing-Tianjin-Hebei metropolitan area and has experienced rapid urbanization in the past few decades. This study aims to elucidate the long-term trends of summer (May-August) high temperatures and explore the affecting mechanism of summer high temperatures on urban heat islands based on 43 years (1978-2020) daily meteorological observation data from the urban station (Beijing Station) and rural station (Miyun and Yanqing Stations). In the past four decades, the summer high-temperature days, intensity, and the yearly extreme maximal air temperature have shown significant increasing trends. Correspondingly, the initial time of summer high-temperature day was markedly advanced, and the end time of summer high-temperature day was significantly delayed. The urban heat island intensity of maximal air temperature significantly decreased, but the urban heat island intensities of mean and minimal air temperature slightly decreased during the summer high-temperature period from 1978 to 2020. The urban heat island intensities of maximal, mean and minimal air temperature during the summer high-temperature period were 0.73 ℃, 1.61 ℃, and 2.40 ℃, which were significantly higher than 0.09 ℃, 0.80 ℃, and 140 ℃ during the summer non-high temperature period from 1978 to 2020. The urban heat island intensity was significantly aggravated (more than 0.6 ℃) during the period with high-temperature compared to the period without high temperature, indicating that the urban heat island effect was amplified by summer high temperature. It is projected that summer high temperatures would become more frequent, and urban heat islands in Beijing would markedly increase under the background of future climate warming and rapid urbanization. These findings underline the serious heatrelated health risks facing urban residents.
2023, 51(1):75-84.
DOI: 10.19517/j.1671-6345.20220009
Abstract:
Based on the hourly rainfall data, the frequency, rainfall and class-conditional probability density of day and night, winter and summer rainfall in different terrain ladder representative districts along the 30°N are statistically analyzed. The influence of different terrain heights with longitude on rainfall is explored by studying the distribution of day-night and winter-sumer ratios of rainfall. The results show that: (1) Along the 30°N, the rainfall and frequency ratio of night to day decreases eastward in the Sichuan Basin. Ya’an is the highvalue centre of strong night rainfall. The phenomenon of night rainfall tends to disappear to the east of 108°E mountain in the east of the Sichuan Basin. Night rainfall is more likely to occur in strong precipitation in the basin than in weak precipitation. (2) There is a big difference between winter and summer rains along the 30°N line. Winter rainfall is small, and summer rainfall is large; structurally, the rain is weak in winter and strong in summer; there are regional differences in frequency. The second topographic step has less winter and more summer rains, while the third topographic step in opposite. Winter rains is more obviously affected by large terrain. (3) According to the cluster analysis of the first kind of Class-Conditional Probability Density 1 (CCPD1) ratio of winter to summer and CCPD1 anomaly percentage of winter rains, the eight sub-regions can be divided into three categories, which have a good corresponding relationship with geographical location and terrain steps. (4) Summer rainfall is significantly affected by local terrain. The peak value area of anomaly percentage of the summer rain CCPD1 higher than 10% ( or valley of lower than -10%) is defined as the summer rain strong (weak) potential area, and the strong and weak potential areas are different. There is a great potential for short-term heavy precipitation in the south of Jianghan Plain and north of Poyang Lake, and there is a great potential for extreme short-term heavy precipitation in Ya’an (the strong potential area ≥ 61 mm). The strong potential area of winter rainfall (the peak area where the anomaly percentage of CCPD1 is higher than 50%) is located in divisions Ⅶ, Ⅷ and Ⅸ on the third topographic step (the potential value is 1 to 20 mm). Still, the precipitation range of 1 to 20 mm is a weak potential area (valley area where anomaly percentage of CCPD1 is lower than -50%) in Ya’an and the basin centre.
Based on the hourly rainfall data, the frequency, rainfall and class-conditional probability density of day and night, winter and summer rainfall in different terrain ladder representative districts along the 30°N are statistically analyzed. The influence of different terrain heights with longitude on rainfall is explored by studying the distribution of day-night and winter-sumer ratios of rainfall. The results show that: (1) Along the 30°N, the rainfall and frequency ratio of night to day decreases eastward in the Sichuan Basin. Ya’an is the highvalue centre of strong night rainfall. The phenomenon of night rainfall tends to disappear to the east of 108°E mountain in the east of the Sichuan Basin. Night rainfall is more likely to occur in strong precipitation in the basin than in weak precipitation. (2) There is a big difference between winter and summer rains along the 30°N line. Winter rainfall is small, and summer rainfall is large; structurally, the rain is weak in winter and strong in summer; there are regional differences in frequency. The second topographic step has less winter and more summer rains, while the third topographic step in opposite. Winter rains is more obviously affected by large terrain. (3) According to the cluster analysis of the first kind of Class-Conditional Probability Density 1 (CCPD1) ratio of winter to summer and CCPD1 anomaly percentage of winter rains, the eight sub-regions can be divided into three categories, which have a good corresponding relationship with geographical location and terrain steps. (4) Summer rainfall is significantly affected by local terrain. The peak value area of anomaly percentage of the summer rain CCPD1 higher than 10% ( or valley of lower than -10%) is defined as the summer rain strong (weak) potential area, and the strong and weak potential areas are different. There is a great potential for short-term heavy precipitation in the south of Jianghan Plain and north of Poyang Lake, and there is a great potential for extreme short-term heavy precipitation in Ya’an (the strong potential area ≥ 61 mm). The strong potential area of winter rainfall (the peak area where the anomaly percentage of CCPD1 is higher than 50%) is located in divisions Ⅶ, Ⅷ and Ⅸ on the third topographic step (the potential value is 1 to 20 mm). Still, the precipitation range of 1 to 20 mm is a weak potential area (valley area where anomaly percentage of CCPD1 is lower than -50%) in Ya’an and the basin centre.
2023, 51(1):85-93.
DOI: 10.19517/j.1671-6345.20210531
Abstract:
The ensembled method is beneficial in improving the accuracy and predictability of precipitation element forecasts. This paper is based on grid data and smart grid forecasts, southwestern regional numerical forecasts, ECMWF model forecasts and GRAPES model forecast data, with area rainfall as the research object, using the multiple regression method, BP neural network method, scoring weight method, weighted ensembled forecasting method and the arithmetic average method to obtain the ensembled areal rainfall forecast, and then the average absolute error, fuzzy score, correct rate, TS score, deviation analysis and other methods are used to compare and analyze the forecast effect of the lower reaches of the Jinsha River from April to October 2020. The results show that the prediction effect of the multiple regression method and the BP neural network method are generally better than those of the other ensemble methods. When considering the forecast magnitude of the area rainfall in the basin, the model and ensemble method with smaller forecast magnitude can be employed downstream. After ensemble, the deviation percentages are reduced, and the multiple regression method and the BP neural network method have a corrective effect on the models with smaller forecast magnitudes. In the forecast of whether there is precipitation, light rain and moderate rain, the multiple regression method has a better ensemble effect. In the heavy rainfall forecast, the BP neural network method has a better ensemble effect. These conclusions can provide references for future surface rainfall forecasting in the river valley.
The ensembled method is beneficial in improving the accuracy and predictability of precipitation element forecasts. This paper is based on grid data and smart grid forecasts, southwestern regional numerical forecasts, ECMWF model forecasts and GRAPES model forecast data, with area rainfall as the research object, using the multiple regression method, BP neural network method, scoring weight method, weighted ensembled forecasting method and the arithmetic average method to obtain the ensembled areal rainfall forecast, and then the average absolute error, fuzzy score, correct rate, TS score, deviation analysis and other methods are used to compare and analyze the forecast effect of the lower reaches of the Jinsha River from April to October 2020. The results show that the prediction effect of the multiple regression method and the BP neural network method are generally better than those of the other ensemble methods. When considering the forecast magnitude of the area rainfall in the basin, the model and ensemble method with smaller forecast magnitude can be employed downstream. After ensemble, the deviation percentages are reduced, and the multiple regression method and the BP neural network method have a corrective effect on the models with smaller forecast magnitudes. In the forecast of whether there is precipitation, light rain and moderate rain, the multiple regression method has a better ensemble effect. In the heavy rainfall forecast, the BP neural network method has a better ensemble effect. These conclusions can provide references for future surface rainfall forecasting in the river valley.
2023, 51(1):94-103.
DOI: 10.19517/j.1671-6345.20220001
Abstract:
Taking the southern Shandong Peninsula coast as an example, the circulation patterns and the causes of the gale are explored using the obliquely rotated T-mode Principal Component Analysis and the fifth generation ECMWF reanalysis data (ERA5). There are five main circulation patterns for gale, and the order is the northwest path of the high-pressure type, behind-trough low-pressure trough type, before-trough low-pressure trough type, Jianghuai cyclone type, and north path of the high-pressure type according to the number of gale days, which is consistent with the order of the gale probability for different types. Winter holds the most gale days of high-pressure type (northwest and north path types), spring holds the most gale days of low-pressure trough (before- and behind-trough types), and spring and autumn hold the most gale days of Jianghuai cyclone type. The causes of the northwest path of high-pressure type gale are the combination of the cold advection, cold high-pressure and the momentum downward-transporting. The cause of the north path of high-pressure type gale is the combination of the cold advection and cold high-pressure. The cause of the before-trough low-pressure type gale is the combination of the warm advection, the highpressure at the ocean and the northeast China low. The cause of the behind-trough low-pressure trough type gale is the combination of the cold advection, the cold high-pressure and the northeast China low. The vorticity advection and warm advection before the trough are the key factors for the development and movement of the low pressure. The Jianghuai cyclone moves northeast and results in a large pressure gradient at the south of the Shandong Peninsula, causing the Jianghuai cyclone type gale.
Taking the southern Shandong Peninsula coast as an example, the circulation patterns and the causes of the gale are explored using the obliquely rotated T-mode Principal Component Analysis and the fifth generation ECMWF reanalysis data (ERA5). There are five main circulation patterns for gale, and the order is the northwest path of the high-pressure type, behind-trough low-pressure trough type, before-trough low-pressure trough type, Jianghuai cyclone type, and north path of the high-pressure type according to the number of gale days, which is consistent with the order of the gale probability for different types. Winter holds the most gale days of high-pressure type (northwest and north path types), spring holds the most gale days of low-pressure trough (before- and behind-trough types), and spring and autumn hold the most gale days of Jianghuai cyclone type. The causes of the northwest path of high-pressure type gale are the combination of the cold advection, cold high-pressure and the momentum downward-transporting. The cause of the north path of high-pressure type gale is the combination of the cold advection and cold high-pressure. The cause of the before-trough low-pressure type gale is the combination of the warm advection, the highpressure at the ocean and the northeast China low. The cause of the behind-trough low-pressure trough type gale is the combination of the cold advection, the cold high-pressure and the northeast China low. The vorticity advection and warm advection before the trough are the key factors for the development and movement of the low pressure. The Jianghuai cyclone moves northeast and results in a large pressure gradient at the south of the Shandong Peninsula, causing the Jianghuai cyclone type gale.
2023, 51(1):104-114.
DOI: 10.19517/j.1671-6345.20210483
Abstract:
In order to study the evolution characteristics of the ZDR column in an isolated cell, the hailing process of an isolated cell on May 8, 2018, is analyzed by using X-band dual-polarization radar data combined with ground observation data and reanalysis data. The results show that: (1) In the development stage of an isolated cell, the ZDR column increased rapidly. After the jump, the number of SWAs (Supercooled Water Areas) and HDGs (High Density Graupels) above the 0 ℃ layer increased sharply, and the change rates were 26.7 bins per minute and 11.8 bins per minute, respectively. In the mature stage, the depth of the ZDR column extended to the nearly -20 ℃ layer, the microphysical reaction in the monomer intensified, the number of hail increased rapidly, and the generation rate was 105.8 bin/min. The ZDR column was transformed into a ZDR hole (ZDR<1) with an area of 210 bins, which indicates the ground hail location. (2) Hail occurred after the collapse of the ZDR column. The height of the ZDR column dropped below -10 ℃ due to the dragging effect of solid precipitation. When the small hail fell below the layer of 0 ℃, it melted and formed a water film on the surface, resulting in the ZDR large value area near the ground during the hail fall. (3) The interaction between the microphysical process and thermal dynamic in the isolated cell promoted the formation and development of the ZDR column. In this paper, the evolution characteristics of the ZDR column in different stages of an isolated hail storm are analyzed, and the corresponding hail storm model is established, which is of great significance to the early warning and prevention of local hails.
In order to study the evolution characteristics of the ZDR column in an isolated cell, the hailing process of an isolated cell on May 8, 2018, is analyzed by using X-band dual-polarization radar data combined with ground observation data and reanalysis data. The results show that: (1) In the development stage of an isolated cell, the ZDR column increased rapidly. After the jump, the number of SWAs (Supercooled Water Areas) and HDGs (High Density Graupels) above the 0 ℃ layer increased sharply, and the change rates were 26.7 bins per minute and 11.8 bins per minute, respectively. In the mature stage, the depth of the ZDR column extended to the nearly -20 ℃ layer, the microphysical reaction in the monomer intensified, the number of hail increased rapidly, and the generation rate was 105.8 bin/min. The ZDR column was transformed into a ZDR hole (ZDR<1) with an area of 210 bins, which indicates the ground hail location. (2) Hail occurred after the collapse of the ZDR column. The height of the ZDR column dropped below -10 ℃ due to the dragging effect of solid precipitation. When the small hail fell below the layer of 0 ℃, it melted and formed a water film on the surface, resulting in the ZDR large value area near the ground during the hail fall. (3) The interaction between the microphysical process and thermal dynamic in the isolated cell promoted the formation and development of the ZDR column. In this paper, the evolution characteristics of the ZDR column in different stages of an isolated hail storm are analyzed, and the corresponding hail storm model is established, which is of great significance to the early warning and prevention of local hails.
2023, 51(1):115-123.
DOI: 10.19517/j.1671-6345.20210315
Abstract:
Using China’s firstgeneration global atmospheric/land surface reanalysis product (CRA), combined with visibility data from the CMA Land Data Assimilation System (CLDAS), automatic weather station and Himawari8 satellite data, the evolution, circulation pattern and boundary layer characteristics of the sustained sea fog process in Qiongzhou Strait from January 21 to 26, 2021 are analyzed, and also the formation mechanisms of two different types of fogs are discussed. The results show that: (1) the fog from January 21 to 22 was the frontal fog formed by the diffusion of cold air in the lower layer, while it turned into the easterly advection fog at the rear of a could high from 23 to 26. (2) During the frontal fog period, influenced by the northerly wind, the wind speed was 1 to 3 m·s-1. During the advection fog period, the wind speed was 4 to 6 m·s-1 due to the influence of easterly wind. (3) In the frontal fog stage, the water vapour convergence centre was located from the South bank of the Qiongzhou Strait to the northeast land of Hainan Island, and the fog began to develop on the land. In the advection fog stage, the water vapour convergence centre was located from the North bank of the Qiongzhou Strait to the east of Hainan Island, and the fog developed from the sea. (4) In the frontal fog stage, the inversion layer developed at the height of about 950 hPa, which was an advection configuration of cold in the lower part and warm in the upper part. In the advection fog stage, warm advection occurred below 950 hPa, and the inversion layer developed from the ground. The development of two kinds of fogs with different properties, frontal fog and advection fog, maintained the fog for a long time.
Using China’s firstgeneration global atmospheric/land surface reanalysis product (CRA), combined with visibility data from the CMA Land Data Assimilation System (CLDAS), automatic weather station and Himawari8 satellite data, the evolution, circulation pattern and boundary layer characteristics of the sustained sea fog process in Qiongzhou Strait from January 21 to 26, 2021 are analyzed, and also the formation mechanisms of two different types of fogs are discussed. The results show that: (1) the fog from January 21 to 22 was the frontal fog formed by the diffusion of cold air in the lower layer, while it turned into the easterly advection fog at the rear of a could high from 23 to 26. (2) During the frontal fog period, influenced by the northerly wind, the wind speed was 1 to 3 m·s-1. During the advection fog period, the wind speed was 4 to 6 m·s-1 due to the influence of easterly wind. (3) In the frontal fog stage, the water vapour convergence centre was located from the South bank of the Qiongzhou Strait to the northeast land of Hainan Island, and the fog began to develop on the land. In the advection fog stage, the water vapour convergence centre was located from the North bank of the Qiongzhou Strait to the east of Hainan Island, and the fog developed from the sea. (4) In the frontal fog stage, the inversion layer developed at the height of about 950 hPa, which was an advection configuration of cold in the lower part and warm in the upper part. In the advection fog stage, warm advection occurred below 950 hPa, and the inversion layer developed from the ground. The development of two kinds of fogs with different properties, frontal fog and advection fog, maintained the fog for a long time.
2023, 51(1):124-133.
DOI: 10.19517/j.1671-6345.20220023
Abstract:
Arid and semi-arid regions of East Asia (“East-Asian drylands”) are the major components of the global arid areas, where water resources are scarce, and dust storms frequently occur. The effects of dust aerosols on atmospheric radiation budget and cloud microphysical processes are nonnegligible over there. By overviewing the research progress of aerosol- and cloud-related issues in the East-Asian drylands, the properties of aerosols and clouds, as well as aerosolcloud interactions, are focused on in this paper. It is found that the aerosols in the East-Asian drylands are dominated by dust aerosols, with the highest optical thickness in spring. Meanwhile, the East-Asian drylands have abundant cloud water resources, which are predominated by high clouds, with higher cloudiness in summer. Dust aerosols can heat the atmosphere by the direct radiative effect and affect the cloud micro-physical processes and precipitation through indirect and semi-direct effects. Due to the limitation of scarce observations and incomplete parameterization in model simulation, there still exist large uncertainties in dust-cloud interactions over the East-Asian drylands. Therefore, reducing the contribution of aerosols and clouds to the uncertainties in climate change research has become an urgent scientific issue in future.
Arid and semi-arid regions of East Asia (“East-Asian drylands”) are the major components of the global arid areas, where water resources are scarce, and dust storms frequently occur. The effects of dust aerosols on atmospheric radiation budget and cloud microphysical processes are nonnegligible over there. By overviewing the research progress of aerosol- and cloud-related issues in the East-Asian drylands, the properties of aerosols and clouds, as well as aerosolcloud interactions, are focused on in this paper. It is found that the aerosols in the East-Asian drylands are dominated by dust aerosols, with the highest optical thickness in spring. Meanwhile, the East-Asian drylands have abundant cloud water resources, which are predominated by high clouds, with higher cloudiness in summer. Dust aerosols can heat the atmosphere by the direct radiative effect and affect the cloud micro-physical processes and precipitation through indirect and semi-direct effects. Due to the limitation of scarce observations and incomplete parameterization in model simulation, there still exist large uncertainties in dust-cloud interactions over the East-Asian drylands. Therefore, reducing the contribution of aerosols and clouds to the uncertainties in climate change research has become an urgent scientific issue in future.
2023, 51(1):134-141.
DOI: 10.19517/j.1671-6345.20210510
Abstract:
Particulate Organic Carbon (POC) in seawater is the basic variable of the marine carbon cycle and plays a key role in the study of the marine carbon cycle. The temporal and spatial variation of POC concentration in the South China Sea is analyzed and discussed based on the POC data set retrieved from the remote sensing data from 2003 to 2020. The results show that the annual average concentration of POC varies from 76.98 to 83.91 mg/m3 in the whole study area. The POC concentration distribution is high in the nearshore and low in the open sea. The POC concentration in the nearshore and shallow waters of the South China Sea is mainly affected by landbased input and coastal current, and the POC concentration in the open sea area is mainly controlled by the circulation and water mass of the South China Sea. The average POC concentration from the first quarter to the fourth quarter is 89.62, 72.90, 79.22 and 84.86 mg/m3. The POC concentration is low in summer and high in winter. The main reason is that the South China Sea is affected by the northeast monsoon in winter and the southwest monsoon in summer, which affects the seawater mixing layer structure in the South China Sea, and phytoplanktons are more prosperous in winter than in summer. On the monthly scale, the POC concentration is the highest in January; the POC concentration decreases rapidly from February to April and reaches the lowest in May; From June to December, the POC concentration begins to rise slowly. The conclusions will provide the decision-making basis for the goverment to deal with such issues as the carbon cycle, carbon peak and carbon neutralization, blue economic development, offshore ecological protection and cope with climate change in the South China Sea.
Particulate Organic Carbon (POC) in seawater is the basic variable of the marine carbon cycle and plays a key role in the study of the marine carbon cycle. The temporal and spatial variation of POC concentration in the South China Sea is analyzed and discussed based on the POC data set retrieved from the remote sensing data from 2003 to 2020. The results show that the annual average concentration of POC varies from 76.98 to 83.91 mg/m3 in the whole study area. The POC concentration distribution is high in the nearshore and low in the open sea. The POC concentration in the nearshore and shallow waters of the South China Sea is mainly affected by landbased input and coastal current, and the POC concentration in the open sea area is mainly controlled by the circulation and water mass of the South China Sea. The average POC concentration from the first quarter to the fourth quarter is 89.62, 72.90, 79.22 and 84.86 mg/m3. The POC concentration is low in summer and high in winter. The main reason is that the South China Sea is affected by the northeast monsoon in winter and the southwest monsoon in summer, which affects the seawater mixing layer structure in the South China Sea, and phytoplanktons are more prosperous in winter than in summer. On the monthly scale, the POC concentration is the highest in January; the POC concentration decreases rapidly from February to April and reaches the lowest in May; From June to December, the POC concentration begins to rise slowly. The conclusions will provide the decision-making basis for the goverment to deal with such issues as the carbon cycle, carbon peak and carbon neutralization, blue economic development, offshore ecological protection and cope with climate change in the South China Sea.
2023, 51(1):142-148.
DOI: 10.19517/j.1671-6345.20220039
Abstract:
Thunderstorm gale is one of the main meteorological disasters affecting railway construction and transport safety. As a trunk railway connecting Sichuan Province and Tibet Region, the Sichuan-Tibet railway is known as the “most difficult railway” because of its complex geographical situation and diverse climate characteristics. This paper aims to quantitatively analyze the wind field characteristics in the Sichuan-Tibet region, provide the scientific basis for the construction of the Sichuan-Tibet railway, and the monitoring, reducing, early warning and risk assessment of disasters along the railway. The spatial distribution characteristics and temporal variation of the wind speed in the Sichuan-Tibet region and along Sichuan-Tibet railway stations are analyzed using the NCEP FNL surface wind data from 2000 to 2020, ground meteorological stations’ wind speed data from 2014 to 2020 and extremely wind speed data from 2006 to 2020. The results show that: (1) The wind force in the west of the Sichuan-Tibet region is higher than that in the east, and the wind speeds in the inland of the plateau are higher than those in the southeast edge of the plateau and Sichuan Province. Wind speed is the largest from November to March of the next year on the plateau, with a monthly average wind speed of more than 7 m/s in the northern and southern edges of the plateau. Wind speeds in summer and autumn are the smallest in the plateau. (2) The wind fields of Lhasa Station, Nyingchi Station, Ya’an Station and Chengdu Station along the Sichuan-Tibet railway are selected for analysis. The wind speeds show a decreasing trend from the west of the plateau to the east. (3) During the study period, the mean wind speed and maximum wind speed along the Sichuan-Tibet Railway show an obvious increasing trend from 2018 to 2020, and the number of strong wind days in Lhasa and Nyingchi also increased. Since 2018, the wind speed along the Sichuan-Tibet railway has increased, and the wind risk to the railway was increasing.
Thunderstorm gale is one of the main meteorological disasters affecting railway construction and transport safety. As a trunk railway connecting Sichuan Province and Tibet Region, the Sichuan-Tibet railway is known as the “most difficult railway” because of its complex geographical situation and diverse climate characteristics. This paper aims to quantitatively analyze the wind field characteristics in the Sichuan-Tibet region, provide the scientific basis for the construction of the Sichuan-Tibet railway, and the monitoring, reducing, early warning and risk assessment of disasters along the railway. The spatial distribution characteristics and temporal variation of the wind speed in the Sichuan-Tibet region and along Sichuan-Tibet railway stations are analyzed using the NCEP FNL surface wind data from 2000 to 2020, ground meteorological stations’ wind speed data from 2014 to 2020 and extremely wind speed data from 2006 to 2020. The results show that: (1) The wind force in the west of the Sichuan-Tibet region is higher than that in the east, and the wind speeds in the inland of the plateau are higher than those in the southeast edge of the plateau and Sichuan Province. Wind speed is the largest from November to March of the next year on the plateau, with a monthly average wind speed of more than 7 m/s in the northern and southern edges of the plateau. Wind speeds in summer and autumn are the smallest in the plateau. (2) The wind fields of Lhasa Station, Nyingchi Station, Ya’an Station and Chengdu Station along the Sichuan-Tibet railway are selected for analysis. The wind speeds show a decreasing trend from the west of the plateau to the east. (3) During the study period, the mean wind speed and maximum wind speed along the Sichuan-Tibet Railway show an obvious increasing trend from 2018 to 2020, and the number of strong wind days in Lhasa and Nyingchi also increased. Since 2018, the wind speed along the Sichuan-Tibet railway has increased, and the wind risk to the railway was increasing.
17 An Hourly Meteorological Model for Fog Accident Discriminant Based on Machine Learning Technology
2023, 51(1):149-156.
DOI: 10.19517/j.1671-6345.20220081
Abstract:
In order to further improve the ability of refined meteorological services for traffic safety in foggy weather, this study takes Jiangsu and Anhui expressway sections where frequent fog-caused accidents happen as examples, with the application of the disaster information and weather data from 2012 to 2018 to establish a support vector machine hybrid model for hourly fog accident detection based on variable selection and feature extraction. The model uses the recursive feature elimination method to select the important variables from accident time, geographic location, and meteorological environment, and then extracts the main features of the important variables by principal component analysis. The radial basis is used as the kernel function, and the optimal parameters are determined by network search. The results show that this support vector machine hybrid model can successfully identify 81.4% of the accident samples in the training set and 83.0% of the test set, and the AUC scores are both 0.946. The ability to identify fog accidents is superior to the support vector machine algorithm and the support vector machine algorithm based only on main variable selection or principal component analysis. The analysis of three typical examples also shows that the support vector machine hybrid model has certain identification and warning significance for the occurrence of traffic accidents under periodic or persistent foggy weather.
In order to further improve the ability of refined meteorological services for traffic safety in foggy weather, this study takes Jiangsu and Anhui expressway sections where frequent fog-caused accidents happen as examples, with the application of the disaster information and weather data from 2012 to 2018 to establish a support vector machine hybrid model for hourly fog accident detection based on variable selection and feature extraction. The model uses the recursive feature elimination method to select the important variables from accident time, geographic location, and meteorological environment, and then extracts the main features of the important variables by principal component analysis. The radial basis is used as the kernel function, and the optimal parameters are determined by network search. The results show that this support vector machine hybrid model can successfully identify 81.4% of the accident samples in the training set and 83.0% of the test set, and the AUC scores are both 0.946. The ability to identify fog accidents is superior to the support vector machine algorithm and the support vector machine algorithm based only on main variable selection or principal component analysis. The analysis of three typical examples also shows that the support vector machine hybrid model has certain identification and warning significance for the occurrence of traffic accidents under periodic or persistent foggy weather.
2023, 51(1):157-166.
DOI: 10.19517/j.1671-6345.20220159
Abstract:
High-resolution spatial information extraction and pollen sensitization risk assessment of Beijing pine and cypress vegetation are of great significance for pollen concentration monitoring and prediction. Based on 304 high-resolution Sentinel-2A multispectral imager (MSI) satellite images in the winter of 2019-2020, the new enhanced normalized vegetation index (EVI) and surface water index (LSWI) are introduced to establish the method of pine and cypress vegetations extraction. The mapping of pine and cypress vegetation distribution in Beijing with 10 m spatial resolution is carried out. At the same time, using the principle of risk assessment, a spatial risk assessment method of pine and cypress pollen sensitization from the spatial distribution of pine and cypress vegetation is established. Combined with the pine and cypress pollen concentration data from the pollen observation stations in 2020, the area size and the optimal spatial distance affecting pollen concentration and the risk assessment of pine and cypress pollen sensitization are studied. The results show that based on a series of processed winter synthetic Sentinel-2A satellite images under clear weather conditions in Beijing, the vegetation of pine and cypress in Beijing can be effectively extracted by using EVI and LSWI thresholds, and the accuracy is more than 80%. The pine and cypress vegetation in Beijing is mainly distributed in the mountains in the north and southwest, followed by the northern plain, while less in the central urban area, Daxing and Tongzhou. The pine and cypress vegetation within 14 km has a positive contribution to the pollen concentration of the station, of which the pine and cypress vegetation within 6 km has the largest contribution. The relatively high-risk areas of pine and cypress pollen sensitization are mainly distributed in the northwest mountainous area, the north of Changping, the east of Mentougou, the northwest of Shijingshan and the southwest of Haidian.
High-resolution spatial information extraction and pollen sensitization risk assessment of Beijing pine and cypress vegetation are of great significance for pollen concentration monitoring and prediction. Based on 304 high-resolution Sentinel-2A multispectral imager (MSI) satellite images in the winter of 2019-2020, the new enhanced normalized vegetation index (EVI) and surface water index (LSWI) are introduced to establish the method of pine and cypress vegetations extraction. The mapping of pine and cypress vegetation distribution in Beijing with 10 m spatial resolution is carried out. At the same time, using the principle of risk assessment, a spatial risk assessment method of pine and cypress pollen sensitization from the spatial distribution of pine and cypress vegetation is established. Combined with the pine and cypress pollen concentration data from the pollen observation stations in 2020, the area size and the optimal spatial distance affecting pollen concentration and the risk assessment of pine and cypress pollen sensitization are studied. The results show that based on a series of processed winter synthetic Sentinel-2A satellite images under clear weather conditions in Beijing, the vegetation of pine and cypress in Beijing can be effectively extracted by using EVI and LSWI thresholds, and the accuracy is more than 80%. The pine and cypress vegetation in Beijing is mainly distributed in the mountains in the north and southwest, followed by the northern plain, while less in the central urban area, Daxing and Tongzhou. The pine and cypress vegetation within 14 km has a positive contribution to the pollen concentration of the station, of which the pine and cypress vegetation within 6 km has the largest contribution. The relatively high-risk areas of pine and cypress pollen sensitization are mainly distributed in the northwest mountainous area, the north of Changping, the east of Mentougou, the northwest of Shijingshan and the southwest of Haidian.
External LinksChina Meteorological AdministrationCMA Meteorological Observation CentreChinese Academy of Meteorological SciencesBeijing Meteorological ServiceNational Satellite Meteorological Center
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.