ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 48,Issue 3,2022 Table of Contents
2022, 48(3):261-271.
DOI: 10.7519/j.issn.1000-0526.2022.022401
Abstract:
In view of the theme of the World Meteorological Day in 2022, this paper reviews the understanding process of the importance of meteorological and hydrological information in the development of atmospheric science, as well as the cooperation experience and results of the international community in the field of meteorological observation and data exchange, especially the achievements and challenges since the establishment of the World Meteorological Organization （WMO）. Finally, the latest achievements of WMO reform in the field of information policy are introduced.
In view of the theme of the World Meteorological Day in 2022, this paper reviews the understanding process of the importance of meteorological and hydrological information in the development of atmospheric science, as well as the cooperation experience and results of the international community in the field of meteorological observation and data exchange, especially the achievements and challenges since the establishment of the World Meteorological Organization （WMO）. Finally, the latest achievements of WMO reform in the field of information policy are introduced.
2022, 48(3):272-283.
DOI: 10.7519/j.issn.1000-0526.2022.022402
Abstract:
High-quality hydrometeorological observation data are the base for the monitoring, forecasting, prediction of hydrometeorological hazards, and also the basic support for long-term climate trend analysis. Focusing on the fundamental elements such as precipitation of water cycle, this paper summarizes the great progress in developing hydrometeorological observation datasets, two and three dimensional fusion analysis products, and multi-dimensional reanalysis products as well as their application in hydrological and climate monitoring and forecasting. The analysis shows that meteorological and hydrological data are two most important embodiments of water cycle in the earth system. Their effective integration and collaborative quality control can effectively promote their application in various components of the earth system model. Produced through intensive data processing such as data fusion analysis and assimilation analysis of multi-source earth observation data, the gridded analysis products with multi spatiotemporal scale, high precision, high timeliness and continuous space-time are used to be the initial points of intelligent grid forecasting and climate prediction, having become an integral part of seamless fine gridded forecasting operation. The global long-series atmospheric and land surface reanalysis products produced by assimilation of historical observational data play important roles in the assessment and monitoring of long-term evolution of climate change, and their application values are far beyond the observation data itself.
High-quality hydrometeorological observation data are the base for the monitoring, forecasting, prediction of hydrometeorological hazards, and also the basic support for long-term climate trend analysis. Focusing on the fundamental elements such as precipitation of water cycle, this paper summarizes the great progress in developing hydrometeorological observation datasets, two and three dimensional fusion analysis products, and multi-dimensional reanalysis products as well as their application in hydrological and climate monitoring and forecasting. The analysis shows that meteorological and hydrological data are two most important embodiments of water cycle in the earth system. Their effective integration and collaborative quality control can effectively promote their application in various components of the earth system model. Produced through intensive data processing such as data fusion analysis and assimilation analysis of multi-source earth observation data, the gridded analysis products with multi spatiotemporal scale, high precision, high timeliness and continuous space-time are used to be the initial points of intelligent grid forecasting and climate prediction, having become an integral part of seamless fine gridded forecasting operation. The global long-series atmospheric and land surface reanalysis products produced by assimilation of historical observational data play important roles in the assessment and monitoring of long-term evolution of climate change, and their application values are far beyond the observation data itself.
3 Influence of Climatological Mean Value Change on Climate Operation in China Under the Global Warming
2022, 48(3):284-298.
DOI: 10.7519/j.issn.1000-0526.2021.111901
Abstract:
The change of climatological mean value indicates the change of climatic average state (hereinafter referred to as climatic state). Due to the difference between different climatic states, when one climate state changes, it will influence the judgment results of variation characteristics of various meteorological elements, atmospheric circulation system and so on. The greater the difference between different climatic states, the more obvious the impact on judgment results, which is the impact of climatic state replacement. How will the new regulation of changing the climate mean value from 1981-2010 to 1991-2020, which will be implemented on 1 January 2022, affect China’s climate monitoring, prediction and evaluation? This is a very concerned problem in our climate operation. In view of the change of the climatological mean value, this paper compares and analyzes the differences and impacts of climatic states in different periods from the aspects of temperature and precipitation at 160 stations in China as well as from the changes of atmospheric circulation and oceanic key factors and so on, and then focuses on the impacts of the new climatic state replacement of 1991-2020. The results show that the influence of climatic states in different periods is different, in which the influence of temperature climatic state replacement is more significant than that of precipitation climatic state replacement, and there are some seasonal differences in this influence. The influence in winter is greater than that in summer, while the influence of precipitation climatic state replacement is mainly concentrated in the two transition seasons of April-June and September-November. By analyzing the influence of the new climatic state, we found that the temperature anomaly in most parts of China decreases, and the maximum decrease area is near Hetao region, with a decrease range of 0.3-0.7℃. The influence of precipitation climatic state replacement mainly occurs in summer and autumn, and the rainy characteristic in southern China in summer and in northern China in autumn weakens; The influence of height climatic state replacement on 500 hPa atmospheric circulation shows that in winter Ural Mountains ridge is strengthened, the East Asian trough is more eastward and the Mongolian high is weakened, while the situation is just the opposite in summer. In terms of the influence on monsoons, the East Asian winter monsoon is weakened, but the summer monsoon is strengthened. In addition, the IOD positive phase weakens and the sea surface temperature (SST) anomaly index in Ni〖AKn~D〗o1+2 region rises.
The change of climatological mean value indicates the change of climatic average state (hereinafter referred to as climatic state). Due to the difference between different climatic states, when one climate state changes, it will influence the judgment results of variation characteristics of various meteorological elements, atmospheric circulation system and so on. The greater the difference between different climatic states, the more obvious the impact on judgment results, which is the impact of climatic state replacement. How will the new regulation of changing the climate mean value from 1981-2010 to 1991-2020, which will be implemented on 1 January 2022, affect China’s climate monitoring, prediction and evaluation? This is a very concerned problem in our climate operation. In view of the change of the climatological mean value, this paper compares and analyzes the differences and impacts of climatic states in different periods from the aspects of temperature and precipitation at 160 stations in China as well as from the changes of atmospheric circulation and oceanic key factors and so on, and then focuses on the impacts of the new climatic state replacement of 1991-2020. The results show that the influence of climatic states in different periods is different, in which the influence of temperature climatic state replacement is more significant than that of precipitation climatic state replacement, and there are some seasonal differences in this influence. The influence in winter is greater than that in summer, while the influence of precipitation climatic state replacement is mainly concentrated in the two transition seasons of April-June and September-November. By analyzing the influence of the new climatic state, we found that the temperature anomaly in most parts of China decreases, and the maximum decrease area is near Hetao region, with a decrease range of 0.3-0.7℃. The influence of precipitation climatic state replacement mainly occurs in summer and autumn, and the rainy characteristic in southern China in summer and in northern China in autumn weakens; The influence of height climatic state replacement on 500 hPa atmospheric circulation shows that in winter Ural Mountains ridge is strengthened, the East Asian trough is more eastward and the Mongolian high is weakened, while the situation is just the opposite in summer. In terms of the influence on monsoons, the East Asian winter monsoon is weakened, but the summer monsoon is strengthened. In addition, the IOD positive phase weakens and the sea surface temperature (SST) anomaly index in Ni〖AKn~D〗o1+2 region rises.
2022, 48(3):299-310.
DOI: 10.7519/j.issn.1000-0526.2021.091801
Abstract:
In this paper, a hybrid variational data assimilation scheme by extended control variable, which introduces flow-dependent background error covariance (statistically described with ensemble forecast perturbations), has been developed based on the CMA-TYM 3DVar system. Tests have shown that the assimilation of single-point typhoon central sea level pressure can cause the formation of asymmetric wind increments, and lead to the appearance of humidity increments that are considered irrelevant with pressure in the traditional 3DVar scheme. Experiments of a typhoon case show that the hybrid En3DVar scheme can effectively extract scattered observation data, and propagate it around according to the actual typhoon dynamic characteristics and distribution area, thereby it will change the structure and intensity of typhoon in the analysis field. At the same time, compared with the traditional 3DVar scheme, the hybrid En3DVar scheme has significant effect in improving the typhoon track and intensity forecast.
In this paper, a hybrid variational data assimilation scheme by extended control variable, which introduces flow-dependent background error covariance (statistically described with ensemble forecast perturbations), has been developed based on the CMA-TYM 3DVar system. Tests have shown that the assimilation of single-point typhoon central sea level pressure can cause the formation of asymmetric wind increments, and lead to the appearance of humidity increments that are considered irrelevant with pressure in the traditional 3DVar scheme. Experiments of a typhoon case show that the hybrid En3DVar scheme can effectively extract scattered observation data, and propagate it around according to the actual typhoon dynamic characteristics and distribution area, thereby it will change the structure and intensity of typhoon in the analysis field. At the same time, compared with the traditional 3DVar scheme, the hybrid En3DVar scheme has significant effect in improving the typhoon track and intensity forecast.
2022, 48(3):311-323.
DOI: 10.7519/j.issn.1000-0526.2022.011801
Abstract:
Based on the NCEP/NCAR reanalysis data， the largescale circulation background and water vapor characteristics of five rainstorm processes in the southern margin of the Taklimakan Desert during May-September (warm season) in 2001-2020 are analyzed and then HYSPLIT （Lagrangian method） method is used to calculate the water vapor trajectory and main path as well as the water vapor contribution of different sources. The results show that the water vapor sources of the rainstorms are mainly the Southwest Asia, central Asia and northern Xinjiang. Water vapor from the source areas passes through northern Pakistan, northwest India, northeast Afghanistan （IPA) and the key areas of southern Xinjiang, respectively into the rainstorm areas from the southwest and north path, the water vapor passing through the key areas of southern Xinjiang contributes a lot to the rainstorm. During the rainstorms on the southern edge of the desert, water vapor in the middle layer of the atmosphere (500 hPa) originates mainly from Southwest Asia, but there is a lot of loss along the way. While in the lower layer (700 hPa), the main contribution of water vapor is from northern Xinjiang, and the loss along the way is small. The water vapor from the northern and southern Xinjiang Basins is mainly transported to 700 hPa from the nearsurface layer. The water vapor from Southwest Asia, the Atlantic Ocean and its coast is transported to the height above 700 hPa. Based on the above features,the three dimensional structure model of water vapor source and path during rainstorm process on the southern edge of the desert is established， and also a more detailed descriptions of the contribution and source of each layer of water vapor are provided.
Based on the NCEP/NCAR reanalysis data， the largescale circulation background and water vapor characteristics of five rainstorm processes in the southern margin of the Taklimakan Desert during May-September (warm season) in 2001-2020 are analyzed and then HYSPLIT （Lagrangian method） method is used to calculate the water vapor trajectory and main path as well as the water vapor contribution of different sources. The results show that the water vapor sources of the rainstorms are mainly the Southwest Asia, central Asia and northern Xinjiang. Water vapor from the source areas passes through northern Pakistan, northwest India, northeast Afghanistan （IPA) and the key areas of southern Xinjiang, respectively into the rainstorm areas from the southwest and north path, the water vapor passing through the key areas of southern Xinjiang contributes a lot to the rainstorm. During the rainstorms on the southern edge of the desert, water vapor in the middle layer of the atmosphere (500 hPa) originates mainly from Southwest Asia, but there is a lot of loss along the way. While in the lower layer (700 hPa), the main contribution of water vapor is from northern Xinjiang, and the loss along the way is small. The water vapor from the northern and southern Xinjiang Basins is mainly transported to 700 hPa from the nearsurface layer. The water vapor from Southwest Asia, the Atlantic Ocean and its coast is transported to the height above 700 hPa. Based on the above features,the three dimensional structure model of water vapor source and path during rainstorm process on the southern edge of the desert is established， and also a more detailed descriptions of the contribution and source of each layer of water vapor are provided.
2022, 48(3):324-333.
DOI: 10.7519/j.issn.1000-0526.2021.112501
Abstract:
The Tibetan Plateau vortex (TPV) is the main precipitation system on the Tibetan Plateau (TP). It often causes heavy rain, torrential rain or even heavy rainstorms in the lower reaches of the TP. After TPV moves off the TP, its moving path is mainly divided into east moving (E-TPV), northeast moving (NE-TPV) and so on. Based on the database of TPV from 1979 to 2018, this paper selects the NE-TPV in early summer (June) as the research object. According to its moving-off position, NE-TPV is divided into the westward vortex (denoted as NEI-TPV) and the eastward vortex (denoted as NEⅡ-TPV). In terms of the source, structure, circulation and influence on precipitation, the two types of NE-TPV are statistically analyzed and compared with the E-TPV. The results show that the source of the NE-TPV is more northerly than the E-TPV. NEⅠ-TPV is mainly generated in the northwestern part of the TP and NEⅡ-TPV is mainly generated in three relatively concentrated areas. After moving off the TP, the maximum ascending region of NEⅠ-TPV is located on the northeast side of the vortex, while the NEⅡ-TPV is similar to the E-TPV with its ascending area mainly located on the southeast side of the vortex. The moving direction and position of the TPV before it moves off are mainly affected by the westerly fluctuations at 200 hPa, and the moving direction after it moves off is mainly affected by the troughs and ridges at 500 hPa in the east of the TP. Among these troughs and ridges, the Hetao high pressure ridge is particularly important in blocking the NE-TPV. The moving speed of the TPV is jointly affected by the altitude difference and its moving direction. The TPV moving eastward often has a faster moving speed. After the NEⅠ-TPV moves off the TP, it mainly affects the Hexi Corridor Area, and the precipitation is dominated by light rain. NEⅡ-TPV mainly affects the eastern part of the northwestern China and nearly 70% of it will cause heavy rain or torrential rain.
The Tibetan Plateau vortex (TPV) is the main precipitation system on the Tibetan Plateau (TP). It often causes heavy rain, torrential rain or even heavy rainstorms in the lower reaches of the TP. After TPV moves off the TP, its moving path is mainly divided into east moving (E-TPV), northeast moving (NE-TPV) and so on. Based on the database of TPV from 1979 to 2018, this paper selects the NE-TPV in early summer (June) as the research object. According to its moving-off position, NE-TPV is divided into the westward vortex (denoted as NEI-TPV) and the eastward vortex (denoted as NEⅡ-TPV). In terms of the source, structure, circulation and influence on precipitation, the two types of NE-TPV are statistically analyzed and compared with the E-TPV. The results show that the source of the NE-TPV is more northerly than the E-TPV. NEⅠ-TPV is mainly generated in the northwestern part of the TP and NEⅡ-TPV is mainly generated in three relatively concentrated areas. After moving off the TP, the maximum ascending region of NEⅠ-TPV is located on the northeast side of the vortex, while the NEⅡ-TPV is similar to the E-TPV with its ascending area mainly located on the southeast side of the vortex. The moving direction and position of the TPV before it moves off are mainly affected by the westerly fluctuations at 200 hPa, and the moving direction after it moves off is mainly affected by the troughs and ridges at 500 hPa in the east of the TP. Among these troughs and ridges, the Hetao high pressure ridge is particularly important in blocking the NE-TPV. The moving speed of the TPV is jointly affected by the altitude difference and its moving direction. The TPV moving eastward often has a faster moving speed. After the NEⅠ-TPV moves off the TP, it mainly affects the Hexi Corridor Area, and the precipitation is dominated by light rain. NEⅡ-TPV mainly affects the eastern part of the northwestern China and nearly 70% of it will cause heavy rain or torrential rain.
2022, 48(3):334-344.
DOI: 10.7519/j.issn.1000-0526.2021.110901
Abstract:
Gust has a significant impact on shipping and offshore production, but there are fewer objective gust forecast products and the time resolution is at a low level for the offshore areas of China. In order to enrich the objective forecast and improve the accuracy of sea gust forecasts, this paper uses the multiple regression method to establish the hourly gust forecast equations for Chinese offshore based on the 2016-2019 observation data and ERA5 reanalysis data, and also uses the 2020 ECMWF deterministic model data for forecasting experiments. Comparing the gust forecast products in the ECMWF deterministic model and gust factor method forecast products in 2020, we find that the gust forecast equation based on the multiple regression method considers the average wind speed term, the near-surface layer turbulence term and the convection term, and it has clear physical and statistical significance and a better fitting effect on gust. In the forecasting of scale 8-9 gust, the average error and the average absolute error of the multiple regression method forecast are lower than the gust forecast by the ECMWF deterministic model, so the forecast effect is better than that of the ECMWF deterministic model in the process of cold air gale weather. At the same time, this method can also reflect the gust situation under the influence of typhoon, and could provide a reference for gust forecast over Chinese offshore areas.
Gust has a significant impact on shipping and offshore production, but there are fewer objective gust forecast products and the time resolution is at a low level for the offshore areas of China. In order to enrich the objective forecast and improve the accuracy of sea gust forecasts, this paper uses the multiple regression method to establish the hourly gust forecast equations for Chinese offshore based on the 2016-2019 observation data and ERA5 reanalysis data, and also uses the 2020 ECMWF deterministic model data for forecasting experiments. Comparing the gust forecast products in the ECMWF deterministic model and gust factor method forecast products in 2020, we find that the gust forecast equation based on the multiple regression method considers the average wind speed term, the near-surface layer turbulence term and the convection term, and it has clear physical and statistical significance and a better fitting effect on gust. In the forecasting of scale 8-9 gust, the average error and the average absolute error of the multiple regression method forecast are lower than the gust forecast by the ECMWF deterministic model, so the forecast effect is better than that of the ECMWF deterministic model in the process of cold air gale weather. At the same time, this method can also reflect the gust situation under the influence of typhoon, and could provide a reference for gust forecast over Chinese offshore areas.
8 Anomalous Characteristics of Regional Torrential Rain in Qinling and Daba Mountains on 23 April 2021
2022, 48(3):345-356.
DOI: 10.7519/j.issn.1000-0526.2021.093002
Abstract:
Using hourly precipitation, radar, FY-4A satellite and other observational data, and ERA5 hourly reanalysis data, this paper analyzes the mesoscale characteristics, moisture and circulation anomalies of the large-scale regional torrential rain process in the Qinling and Daba Mountains on 23 April 2021. The results showed that the heavy rain occurred in a large area, and the precipitation at many stations broke through the historical extreme values. Meanwhile abrupt extreme torrential rain attacked the Daba Mountains. At 500 hPa, the abnormal “high in the east and low in the west” circulation situation over the Qinling and Daba Mountainous area increased the pressure gradient between Shaanxi and the western Qinghai-Tibet Plateau, causing the mid-level westerly airflow to have increased. At the same time, the superimposition of the mid- and low-level multi-scale weather systems provided the background dynamic condition for the torrential rain. The southeast airflow in front of the southwest vortex and the easterly wind on the north side formed a shear line that caused the convergence ascending motion of the environmental field while the other side transported the water vapor brought by the southwesterly airflow and the southerly airflow to the Qinling and Daba Mountains to converge. The circulation associated with the long-distance typhoon and the northeast cold vortex activity in the same period caused the abnormal water vapor transportation (30%) of the northeast path to be the unique source of water vapor for this torrential rain process. Compared with the same period in history, the specific humidity on the water vapor path of the south passage and the northeast passage was abnormally positive, indicating that there was abundant water vapor during the torrential rain period. The torrential rain process was mainly caused by the activity of a mesoscale convective system (MCS) in front of the southwest vortex. The topographical uplift of the windward slope of the Daba Mountains and the convergent ascending of the southerly airflow in the environmental field were superimposed. Sufficient water vapor at the lower level was transported vertically to the upper level by strong ascending motion, with strong convective activity, severe hourly rainfall and strong abruptness. However in the Qinling Mountains, the easterly wind converged and rose in front of the mountain, and the ascending movement of the environment field with southwestern airflow in the middle layer was weaker than that in the Daba Mountainous area during the severe precipitation period, and was dominated by stratiform precipitation. But the severe precipitation lasted for a long time, so the accumulated precipitation was a lot. In a word, multi-scale system interactions, abnormal water vapor transport combined with topographical influence under abnormal circulation conditions are the main reasons for the occurrence of this torrential rain process in the Qinling and Daba Mountains.
Using hourly precipitation, radar, FY-4A satellite and other observational data, and ERA5 hourly reanalysis data, this paper analyzes the mesoscale characteristics, moisture and circulation anomalies of the large-scale regional torrential rain process in the Qinling and Daba Mountains on 23 April 2021. The results showed that the heavy rain occurred in a large area, and the precipitation at many stations broke through the historical extreme values. Meanwhile abrupt extreme torrential rain attacked the Daba Mountains. At 500 hPa, the abnormal “high in the east and low in the west” circulation situation over the Qinling and Daba Mountainous area increased the pressure gradient between Shaanxi and the western Qinghai-Tibet Plateau, causing the mid-level westerly airflow to have increased. At the same time, the superimposition of the mid- and low-level multi-scale weather systems provided the background dynamic condition for the torrential rain. The southeast airflow in front of the southwest vortex and the easterly wind on the north side formed a shear line that caused the convergence ascending motion of the environmental field while the other side transported the water vapor brought by the southwesterly airflow and the southerly airflow to the Qinling and Daba Mountains to converge. The circulation associated with the long-distance typhoon and the northeast cold vortex activity in the same period caused the abnormal water vapor transportation (30%) of the northeast path to be the unique source of water vapor for this torrential rain process. Compared with the same period in history, the specific humidity on the water vapor path of the south passage and the northeast passage was abnormally positive, indicating that there was abundant water vapor during the torrential rain period. The torrential rain process was mainly caused by the activity of a mesoscale convective system (MCS) in front of the southwest vortex. The topographical uplift of the windward slope of the Daba Mountains and the convergent ascending of the southerly airflow in the environmental field were superimposed. Sufficient water vapor at the lower level was transported vertically to the upper level by strong ascending motion, with strong convective activity, severe hourly rainfall and strong abruptness. However in the Qinling Mountains, the easterly wind converged and rose in front of the mountain, and the ascending movement of the environment field with southwestern airflow in the middle layer was weaker than that in the Daba Mountainous area during the severe precipitation period, and was dominated by stratiform precipitation. But the severe precipitation lasted for a long time, so the accumulated precipitation was a lot. In a word, multi-scale system interactions, abnormal water vapor transport combined with topographical influence under abnormal circulation conditions are the main reasons for the occurrence of this torrential rain process in the Qinling and Daba Mountains.
2022, 48(3):357-371.
DOI: 10.7519/j.issn.1000-0526.2021.071301
Abstract:
The total performance of short-range torrential rain forecasts during the 2020 Jiangsu main flood season (June-September) is verified based on the three global models (ECMWF, NCEP-GFS, CMA-GFS), three regional models (CMA-MESO, CMA-SH9, PWAFS), local objective forecast commonly used in Jiangsu operational forecast service and subjective forecast by forecasters. Verification and case analyses of stable and convective torrential rain forecast are also demonstrated respectively according to the types of precipitation. Results show that from the overall verification, the subjective torrential rain forecasts of forecasters only have positive TS skill compared to ECMWF within the 24 h forecast lead time. The torrential rain forecasts by local objective method and forecasters have TS>regional models>global models except ECMWF. It is not true that the higher model resolution, the better forecast performance for either global models or regional models. Most regional models have obviously larger torrential rain foreacst area and high false alarm ratio, while most global models except ECMWF have obviously smaller torrential rain forecast area and high miss rate. The CMA-MESO model initialized at 20:00 BT has obviously better forecast performance than that initialized at 08:00 BT. For stable torrential rain forecast, forecasters should take more references of the ECMWF forecasts, the local objective forecasts within 48 h lead time and the CMA-MESO forecasts initialized at 20:00 BT. As for convective torrential rain forecast, forecasters should refer to the region models CMA-SH9, PWAFS, and the 24 h local objective forecasts more.
The total performance of short-range torrential rain forecasts during the 2020 Jiangsu main flood season (June-September) is verified based on the three global models (ECMWF, NCEP-GFS, CMA-GFS), three regional models (CMA-MESO, CMA-SH9, PWAFS), local objective forecast commonly used in Jiangsu operational forecast service and subjective forecast by forecasters. Verification and case analyses of stable and convective torrential rain forecast are also demonstrated respectively according to the types of precipitation. Results show that from the overall verification, the subjective torrential rain forecasts of forecasters only have positive TS skill compared to ECMWF within the 24 h forecast lead time. The torrential rain forecasts by local objective method and forecasters have TS>regional models>global models except ECMWF. It is not true that the higher model resolution, the better forecast performance for either global models or regional models. Most regional models have obviously larger torrential rain foreacst area and high false alarm ratio, while most global models except ECMWF have obviously smaller torrential rain forecast area and high miss rate. The CMA-MESO model initialized at 20:00 BT has obviously better forecast performance than that initialized at 08:00 BT. For stable torrential rain forecast, forecasters should take more references of the ECMWF forecasts, the local objective forecasts within 48 h lead time and the CMA-MESO forecasts initialized at 20:00 BT. As for convective torrential rain forecast, forecasters should refer to the region models CMA-SH9, PWAFS, and the 24 h local objective forecasts more.
2022, 48(3):372-385.
DOI: 10.7519/j.issn.1000-0526.2021.070501
Abstract:
In this study, we propose a new way to obtain motion vectors for extrapolation nowcasting， namely the adaptive-scale tracking radar echoes by correlation （ATREC）, which can automatically adjust the size of tracking area according to the scale of convection systems. ATREC method tracks the large-scale motion of the radar echo which is identified by the automatically determined convection edges, then the different subscale motions are deduced by tracing the self-split small parts of radar echoes. ATREC method can retrieve the motions of different scales of the convection system and get a smooth motion field for extrapolation. Thereafter, this method can resolve the problems caused by the fixed size of tracking area applied in the traditional tracking radar echoes by correlation (TREC) methods, especially the inapplicability of TREC methods in small-scale convective systems. Nowcasting experiments using the ATREC method and MTREC (multi-scale tracking radar echoes by correlation) method are carried out in this study to demonstrate the practical ability of the ATREC method. Comparison based on a series of weather cases shows that the ATREC method has the abilities of automatically analyzing and flexibly adjusting convective systems with different scales and different types. The evaluation scores of case study and the statistic verifications based on 128 cases in April 2016 indicate that ATREC method has better performance than the MTREC method.
In this study, we propose a new way to obtain motion vectors for extrapolation nowcasting， namely the adaptive-scale tracking radar echoes by correlation （ATREC）, which can automatically adjust the size of tracking area according to the scale of convection systems. ATREC method tracks the large-scale motion of the radar echo which is identified by the automatically determined convection edges, then the different subscale motions are deduced by tracing the self-split small parts of radar echoes. ATREC method can retrieve the motions of different scales of the convection system and get a smooth motion field for extrapolation. Thereafter, this method can resolve the problems caused by the fixed size of tracking area applied in the traditional tracking radar echoes by correlation (TREC) methods, especially the inapplicability of TREC methods in small-scale convective systems. Nowcasting experiments using the ATREC method and MTREC (multi-scale tracking radar echoes by correlation) method are carried out in this study to demonstrate the practical ability of the ATREC method. Comparison based on a series of weather cases shows that the ATREC method has the abilities of automatically analyzing and flexibly adjusting convective systems with different scales and different types. The evaluation scores of case study and the statistic verifications based on 128 cases in April 2016 indicate that ATREC method has better performance than the MTREC method.
2022, 48(3):386-392.
DOI: 10.7519/j.issn.1000-0526.2022.021101
Abstract:
The main characteristics of the general atmospheric circulation in December 2021 are as follows. There were two polar vortex centers in the Northern Hemisphere. The East Asian major trough was strong and westward. The northwestern Pacific subtropical high was close to the normal situation. The monthly mean precipitation amount was 8.7 mm, which is 17.1% less than normal (10.5 mm). The monthly mean temperature was -2.3℃, which is 0.9℃ higher than normal (-3.2℃). There were three nationwide cold wave processes and one large-scale fog-haze processe in this month. In addition, Super Typhoon Rai slammed head-on into the Spratly Islands.
The main characteristics of the general atmospheric circulation in December 2021 are as follows. There were two polar vortex centers in the Northern Hemisphere. The East Asian major trough was strong and westward. The northwestern Pacific subtropical high was close to the normal situation. The monthly mean precipitation amount was 8.7 mm, which is 17.1% less than normal (10.5 mm). The monthly mean temperature was -2.3℃, which is 0.9℃ higher than normal (-3.2℃). There were three nationwide cold wave processes and one large-scale fog-haze processe in this month. In addition, Super Typhoon Rai slammed head-on into the Spratly Islands.
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ISSN:1000-0526 CN:11-2282/P