ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 49,Issue 10,2023 Table of Contents
2023, 49(10):1157-1170.
DOI: 10.7519/j.issn.1000-0526.2023.032002
Abstract:
A laser optical disdrometer (HY-P1000) and a two-dimensional video disdrometer (2DVD) were used to measure the raindrop size distribution (DSD) at the Longmen, Xinfeng and Fogang weather stations in Guangdong Province. Differences between the DSD measured by HY-P1000 and 2DVD and the accuracy of precipitation retrieval in the same place and same time were analyzed. The fundamental equations used for quantitative precipitation estimation (QPE) algorithm were fitted by the disdrometer data collected during 2018 and 2019, and then the optimization rainfall algorithm (HCA-QPE) based on the equations above was applied to Guangzhou S-band dual polarization weather radar to improve the accuracy of QPE in Guangdong. The results showed that the 2DVD is more sensitive to small rain drops (<1 mm) while the HY-P1000 can measure much more rain drops larger than 3.5 mm. The polarization parameters retrieved from two types of disdrometers are different from those observed by S-band dual-polarization radar at 0.5° elevation, and the difference of differential reflectivity was relatively large. What’s more, using 2DVD observation data can improve the QPE accuracy of S-band dual polarization radar, especially for light to moderate rainfall.
A laser optical disdrometer (HY-P1000) and a two-dimensional video disdrometer (2DVD) were used to measure the raindrop size distribution (DSD) at the Longmen, Xinfeng and Fogang weather stations in Guangdong Province. Differences between the DSD measured by HY-P1000 and 2DVD and the accuracy of precipitation retrieval in the same place and same time were analyzed. The fundamental equations used for quantitative precipitation estimation (QPE) algorithm were fitted by the disdrometer data collected during 2018 and 2019, and then the optimization rainfall algorithm (HCA-QPE) based on the equations above was applied to Guangzhou S-band dual polarization weather radar to improve the accuracy of QPE in Guangdong. The results showed that the 2DVD is more sensitive to small rain drops (<1 mm) while the HY-P1000 can measure much more rain drops larger than 3.5 mm. The polarization parameters retrieved from two types of disdrometers are different from those observed by S-band dual-polarization radar at 0.5° elevation, and the difference of differential reflectivity was relatively large. What’s more, using 2DVD observation data can improve the QPE accuracy of S-band dual polarization radar, especially for light to moderate rainfall.
2023, 49(10):1171-1186.
DOI: 10.7519/j.issn.1000-0526.2023.051601
Abstract:
Using hourly precipitation data, conventional meteorological observations, Yinchuan CA Radar data and ERA5 high resolution reanalysis data from 2006 to 2021, this paper studies the temporal and spatial correlations between the low-level jet and the rainstorm process in the eastern region of the Helan Mountains, and discusses initially the possible impact mechanism for low-level jets to affect the occurrence and development of rainstorm. The results show that the low-level jets that influence the rainstorms in the eastern foot of the Helan Mountains are mainly distributed in three key areas, i.e., the southern Hetao Region, southeastern Ningxia Hui Autonomons Region and southwestern Shanxi Province, corresponding to southerly jet at 700 hPa, southern jet at 775 hPa and southeastern jet at 850 hPa, respectively. The southeast of Ningxia is a key transfer zone where three low-level jets merge before their continuously developing towards north and west, and has much more prominent impact on the occurrence and development of the rainstorm process in the eastern region of Helan Mountains. According to the height of the maximum wind speed axis of the low-level jet, the low-level jet processes affecting the rainstorm processes in the eastern region of Helan Mountains are divided into seven types. Among them, the frequency of the three levels jet pattern is the highest, accounting for about 54.5% of the total processes, followed by the processes during which the jet streams at 700 hPa and 775 hPa occur simultaneously (36.5%). The occurrence of rainstorm processes is consistent with the low-level jets in time. To be illustrated, the onsets of low-level jets at 700, 775 and 850 hPa are 18, 10 and 7 hours earlier on average than the beginning of rainstorms. The maximum wind speeds of low-level jets at 700 hPa and 775 hPa jet stream are 54 min and 18 min earlier than the appearance of the maximum rainfall intensities of rainstorm process, while the maximum wind speed of low-level jet at 850 hPa lags 12 min on average behind the occurrence of maximum intensity of rainstorm process. The frequencies of 850 hPa Level-Ⅰ jet and 775 hPa Level-Ⅱ jet are more indicative of the frequency of short-term rainstorm of 20-40 mm·h-1 and 40-60 mm·h-1 respectively, whereas the average wind speed of low-level jet at 700 hPa in the key area in the south of Hetao is more indicative of the maximum rainfall intensity of the rainstorm process. In addition, there exists also spatial consistency between rainstorm process and low-level jet, that is, as the low-level jet builds, strengthens and moves towards north or west, or weakens and retreats eastward or southward, the rainstorm starts, intensifies and weakens, and the location of rainstorm is found in the left front of the jet axis. With the effect of the topography of Helan Mountains, the low-level jet moves northward and westward, triggering multiple convective cells in front of the east slope of the mountain, merging and strengthening to form a linear echo with slow movement, strong development, highly organized and obvious train effect, thus very prone to cause the localized severe convective rainstorms to occur in the Helan Mountains Region.
Using hourly precipitation data, conventional meteorological observations, Yinchuan CA Radar data and ERA5 high resolution reanalysis data from 2006 to 2021, this paper studies the temporal and spatial correlations between the low-level jet and the rainstorm process in the eastern region of the Helan Mountains, and discusses initially the possible impact mechanism for low-level jets to affect the occurrence and development of rainstorm. The results show that the low-level jets that influence the rainstorms in the eastern foot of the Helan Mountains are mainly distributed in three key areas, i.e., the southern Hetao Region, southeastern Ningxia Hui Autonomons Region and southwestern Shanxi Province, corresponding to southerly jet at 700 hPa, southern jet at 775 hPa and southeastern jet at 850 hPa, respectively. The southeast of Ningxia is a key transfer zone where three low-level jets merge before their continuously developing towards north and west, and has much more prominent impact on the occurrence and development of the rainstorm process in the eastern region of Helan Mountains. According to the height of the maximum wind speed axis of the low-level jet, the low-level jet processes affecting the rainstorm processes in the eastern region of Helan Mountains are divided into seven types. Among them, the frequency of the three levels jet pattern is the highest, accounting for about 54.5% of the total processes, followed by the processes during which the jet streams at 700 hPa and 775 hPa occur simultaneously (36.5%). The occurrence of rainstorm processes is consistent with the low-level jets in time. To be illustrated, the onsets of low-level jets at 700, 775 and 850 hPa are 18, 10 and 7 hours earlier on average than the beginning of rainstorms. The maximum wind speeds of low-level jets at 700 hPa and 775 hPa jet stream are 54 min and 18 min earlier than the appearance of the maximum rainfall intensities of rainstorm process, while the maximum wind speed of low-level jet at 850 hPa lags 12 min on average behind the occurrence of maximum intensity of rainstorm process. The frequencies of 850 hPa Level-Ⅰ jet and 775 hPa Level-Ⅱ jet are more indicative of the frequency of short-term rainstorm of 20-40 mm·h-1 and 40-60 mm·h-1 respectively, whereas the average wind speed of low-level jet at 700 hPa in the key area in the south of Hetao is more indicative of the maximum rainfall intensity of the rainstorm process. In addition, there exists also spatial consistency between rainstorm process and low-level jet, that is, as the low-level jet builds, strengthens and moves towards north or west, or weakens and retreats eastward or southward, the rainstorm starts, intensifies and weakens, and the location of rainstorm is found in the left front of the jet axis. With the effect of the topography of Helan Mountains, the low-level jet moves northward and westward, triggering multiple convective cells in front of the east slope of the mountain, merging and strengthening to form a linear echo with slow movement, strong development, highly organized and obvious train effect, thus very prone to cause the localized severe convective rainstorms to occur in the Helan Mountains Region.
2023, 49(10):1187-1202.
DOI: 10.7519/j.issn.1000-0526.2023.032201
Abstract:
This study is concerned with a nocturnal convective process from the night of the 24th to the early morning of the 25th September 2017. The meso-β scale convective system on the south side of the frontal rainband perpendicular to the quasi-east-west frontal orientation gradually evolved into a bow echo, causing short-time severe precipitation in the middle and lower reaches of the Yangtze River, accompanied by Level 7 thunderstorm gale. From the perspective of the large-scale environment, there is no favorable thermodynamic conditions at night. Therefore it is difficult to make a forecast. In this study observations and numerical simulations are used to analyze the fomation mechanism. The radar observations show that there is a northeast-southwest meso-β scale convective belt, moving in the south-easterly direction, and there are new convective cells being triggered on its southwest side, forming the lateral back-building propagation. The new cells then merge into the main convective zone. Other new cells, generated ahead (southeast side) of the main convective zone, gradually develop into a northwest-southeast belt and move to the northeast, eventually making the original main northeast-southwest convective belt gradually strengthen and finally evolve into a bow echo. Although the high-resolution numerical model simulation results deviate from observations in intensity and time, the convective system evolution processes are very close to the observations. Therefore, the vertical vorticity equation is used to diagnose the mechanism. The results show that the vorticity tilt term plays an important role in the lateral back-building propagation. In the early stage of the convection development, new cells are generated on the southwest side under the effect of the vorticity tilt term and merge with the main echo. As the echoes continuously merge and strengthen, the divergence term becomes more important and the positive vorticity of the main echo increases significantly under both the vorticity tilt term and the divergence term. Besides, the vorticity vertical transport term propagates the positive vorticity upward, which is beneficial to the vertical extension of the main convection. New cells are triggered in front of the main echo due to the effect of the vorticity horizontal advection term. However, the vertical extension height is low, so it moves northeastward guided by the low-level wind. Its vorticity increases during the movement and it aligns into a northwest-southeast band, which finally leads to the conversion of the linear main echo into the bow echo. The formation of this bow echo differs significantly from the classical model which has the rear inflow jets in the rear part of the bow echo. On the contrary, this case is mainly influenced by the development of convective systems within the warm zone and has a significant frontal near-surface inflow.
This study is concerned with a nocturnal convective process from the night of the 24th to the early morning of the 25th September 2017. The meso-β scale convective system on the south side of the frontal rainband perpendicular to the quasi-east-west frontal orientation gradually evolved into a bow echo, causing short-time severe precipitation in the middle and lower reaches of the Yangtze River, accompanied by Level 7 thunderstorm gale. From the perspective of the large-scale environment, there is no favorable thermodynamic conditions at night. Therefore it is difficult to make a forecast. In this study observations and numerical simulations are used to analyze the fomation mechanism. The radar observations show that there is a northeast-southwest meso-β scale convective belt, moving in the south-easterly direction, and there are new convective cells being triggered on its southwest side, forming the lateral back-building propagation. The new cells then merge into the main convective zone. Other new cells, generated ahead (southeast side) of the main convective zone, gradually develop into a northwest-southeast belt and move to the northeast, eventually making the original main northeast-southwest convective belt gradually strengthen and finally evolve into a bow echo. Although the high-resolution numerical model simulation results deviate from observations in intensity and time, the convective system evolution processes are very close to the observations. Therefore, the vertical vorticity equation is used to diagnose the mechanism. The results show that the vorticity tilt term plays an important role in the lateral back-building propagation. In the early stage of the convection development, new cells are generated on the southwest side under the effect of the vorticity tilt term and merge with the main echo. As the echoes continuously merge and strengthen, the divergence term becomes more important and the positive vorticity of the main echo increases significantly under both the vorticity tilt term and the divergence term. Besides, the vorticity vertical transport term propagates the positive vorticity upward, which is beneficial to the vertical extension of the main convection. New cells are triggered in front of the main echo due to the effect of the vorticity horizontal advection term. However, the vertical extension height is low, so it moves northeastward guided by the low-level wind. Its vorticity increases during the movement and it aligns into a northwest-southeast band, which finally leads to the conversion of the linear main echo into the bow echo. The formation of this bow echo differs significantly from the classical model which has the rear inflow jets in the rear part of the bow echo. On the contrary, this case is mainly influenced by the development of convective systems within the warm zone and has a significant frontal near-surface inflow.
2023, 49(10):1203-1214.
DOI: 10.7519/j.issn.1000-0526.2023.071901
Abstract:
The mountain-valley circulation is a local circulation driven by thermal energy. Wuyishan City is surrounded by mountains on three sides and the center is a hilly area, making the mountain-valley circulation prevalent throughout the year. Based on the data of surface observation station, boundary wind-detecting lidar, and Aeolus (Atmospheric Dynamics Mission Aeolus) lidar satellite, this paper analyzes the characteristics of mountain-valley circulation in Wuyi Mountains. The results show that the mountain-valley wind days are the most in summer. The diurnal variation characteristics of atmosphere in mountain-valley wind days are significant. During the period of mountain wind, the primary wind direction is northerly, the wind speed is small, the low-altitude lidar signal-noise ratio is strong, and vertical movement of air is mainly sinking, forming a circulation cycle in the vertical direction. Oppositely, the valley wind period is dominated by the southerly wind, which is stronger than that in the mountain wind period, the low-altitude lidar signal-noise ratio is weakened, and the vertical movement is dominated by updraft. According to the wind profile of the lidar data fusion, the non-valley wind days in Wuyi Mountains appear under the weather conditions in which southerly wind prevails in the middle and lower layers of troposphere. The southerly wind transports water vapor to the local area, causing the local low altitude to be covered by thicker clouds or precipitation, thus weakening the thermal difference between mountains and valleys, which breaks the local thermal circulation, so mountain-valley wind cannot form.
The mountain-valley circulation is a local circulation driven by thermal energy. Wuyishan City is surrounded by mountains on three sides and the center is a hilly area, making the mountain-valley circulation prevalent throughout the year. Based on the data of surface observation station, boundary wind-detecting lidar, and Aeolus (Atmospheric Dynamics Mission Aeolus) lidar satellite, this paper analyzes the characteristics of mountain-valley circulation in Wuyi Mountains. The results show that the mountain-valley wind days are the most in summer. The diurnal variation characteristics of atmosphere in mountain-valley wind days are significant. During the period of mountain wind, the primary wind direction is northerly, the wind speed is small, the low-altitude lidar signal-noise ratio is strong, and vertical movement of air is mainly sinking, forming a circulation cycle in the vertical direction. Oppositely, the valley wind period is dominated by the southerly wind, which is stronger than that in the mountain wind period, the low-altitude lidar signal-noise ratio is weakened, and the vertical movement is dominated by updraft. According to the wind profile of the lidar data fusion, the non-valley wind days in Wuyi Mountains appear under the weather conditions in which southerly wind prevails in the middle and lower layers of troposphere. The southerly wind transports water vapor to the local area, causing the local low altitude to be covered by thicker clouds or precipitation, thus weakening the thermal difference between mountains and valleys, which breaks the local thermal circulation, so mountain-valley wind cannot form.
2023, 49(10):1215-1226.
DOI: 10.7519/j.issn.1000-0526.2023.083102
Abstract:
Based on conventional observation data, frequently observed data of automatic weather station, Doppler weather radar data and ERA5 reanalysis data, the mesoscale causes for a rarely-seen extreme thunderstorm gale in the central part of Jilin Province on the morning of 9 September 2021 is analyzed. The results show that the squall line system that produced thunderstorm was formed by the deep northeast cold vortex and the large-scale frontogenesis at the tail of the cold front. The strong dry air in middle layer and the temperature lapse rate closed to dry adiabatic below the inversion layer were conducive to the generation of extreme thunderstorm gale. The existence of dry and warm cover led to rapid enhancement of low-level warm and humid air, and the CAPE value surpassed 1600 J·kg-1 at the nearing moment, which made the stratification become extremely unstable in a short period of time. The average wind speed in the entrainment layer was above 20 m·s-1, and the downward transfer of momentum was beneficial to the enhancement of ground wind speed. The extreme thunderstorm gale occurred near the meso-γ scale vortex in the tail front of squall line after fracture, but the causes for the extreme thunderstorm gale at the two stations near the vortex were obviously different, of which the thunderstorm gale at Nongda Station occurred when the air pressure dropped sharply, the temperature rose sharply and the minute precipitation was weak. Thus, it was caused by the strong sinking divergent airflow (cold pool outflow) in front of the squall line accelerating into the vortex under the action of strong southerly airflow, and the convergence updraft was rapidly enhanced. It was significantly different from the extreme thunderstorm gale caused by the strong sinking divergent airflow formed by the drag of precipitation particles at the nearby Nongboyuan Station and Changchun Station.
Based on conventional observation data, frequently observed data of automatic weather station, Doppler weather radar data and ERA5 reanalysis data, the mesoscale causes for a rarely-seen extreme thunderstorm gale in the central part of Jilin Province on the morning of 9 September 2021 is analyzed. The results show that the squall line system that produced thunderstorm was formed by the deep northeast cold vortex and the large-scale frontogenesis at the tail of the cold front. The strong dry air in middle layer and the temperature lapse rate closed to dry adiabatic below the inversion layer were conducive to the generation of extreme thunderstorm gale. The existence of dry and warm cover led to rapid enhancement of low-level warm and humid air, and the CAPE value surpassed 1600 J·kg-1 at the nearing moment, which made the stratification become extremely unstable in a short period of time. The average wind speed in the entrainment layer was above 20 m·s-1, and the downward transfer of momentum was beneficial to the enhancement of ground wind speed. The extreme thunderstorm gale occurred near the meso-γ scale vortex in the tail front of squall line after fracture, but the causes for the extreme thunderstorm gale at the two stations near the vortex were obviously different, of which the thunderstorm gale at Nongda Station occurred when the air pressure dropped sharply, the temperature rose sharply and the minute precipitation was weak. Thus, it was caused by the strong sinking divergent airflow (cold pool outflow) in front of the squall line accelerating into the vortex under the action of strong southerly airflow, and the convergence updraft was rapidly enhanced. It was significantly different from the extreme thunderstorm gale caused by the strong sinking divergent airflow formed by the drag of precipitation particles at the nearby Nongboyuan Station and Changchun Station.
2023, 49(10):1227-1234.
DOI: 10.7519/j.issn.1000-0526.2023.082901
Abstract:
Based on the daily observations of precipitation and sunshine duration from China Meteorological Administration and the NCEP/NCAR reanalysis data, this paper analyzes the extremity features of a high-impact “wheat-soaked persistent rainfall” event in the Huang-Huai-Hai Plain, which covers the five provinces of Hebei, Shandong, Henan, Jiangsu and Anhui, in late May of 2023 and the atmospheric circulation patterns. The findings suggest that, for the dekad average of five provinces during 21-31 May, the extremity of absent sunshine is more intense than precipitation. However, obvious differences exist among the five provinces, of which the situation in Henan Province is the most serious. To compare both the weather condition and the circulation pattern with historical events, this paper proposes an objective definition of “wheat-soaked persistent rainfall” event in Henan Province for the first time and selects out 18 typical cases during 1981-2022. For the “wheat-soaked persistent rainfall” event in late May 2023, it has the sixth highest rainfall amount and the second lowest sunshine duration among all events. The synthesis of general circulation patterns displays a more westward-northward and stronger western Pacific subtropical high (WPSH), and a “lower in the west while higher in the east” geopotential height anomaly in the mid-high latitudes of Eurasia. Therefore, for Henan Province, the extremity of absent sunshine is more obvious. The results of the synthesis of all events from 1981 to 2022 show that the large-scale atmospheric circulation pattern that causes the “wheat-soaked persistent rainfall” event is that the WPSH is westward stronger and the its western ridge line is northward, while the middle and high latitudes of Eurasia are under the “low in the west and high in the east” circulation pattern. In contrast, the circulation pattern of the “wheat-soaked persistent rainfall” event in late May 2023 is similar to that of the historical events in the mid-high latitudes. However, in tropical regions, affected by the Super Typhoon Mawar, the western section of the WPSH is squeezed and deformed, and the moisture transport by the southwesterly wind in the northwest side of the WPSH is significantly much stronger. At the same time, because “Mawar” remain stable near the east of the Philippines for a long time, the southeast wind flow guide by the northeast side of the typhoon is stronger than the southwest wind anomaly on the northwest side of the subtropical high. The two branches of water vapor superpose, leading to persistent precipitation and long-time absence of sunshine in the Huang-Huai-Hai Plain.
Based on the daily observations of precipitation and sunshine duration from China Meteorological Administration and the NCEP/NCAR reanalysis data, this paper analyzes the extremity features of a high-impact “wheat-soaked persistent rainfall” event in the Huang-Huai-Hai Plain, which covers the five provinces of Hebei, Shandong, Henan, Jiangsu and Anhui, in late May of 2023 and the atmospheric circulation patterns. The findings suggest that, for the dekad average of five provinces during 21-31 May, the extremity of absent sunshine is more intense than precipitation. However, obvious differences exist among the five provinces, of which the situation in Henan Province is the most serious. To compare both the weather condition and the circulation pattern with historical events, this paper proposes an objective definition of “wheat-soaked persistent rainfall” event in Henan Province for the first time and selects out 18 typical cases during 1981-2022. For the “wheat-soaked persistent rainfall” event in late May 2023, it has the sixth highest rainfall amount and the second lowest sunshine duration among all events. The synthesis of general circulation patterns displays a more westward-northward and stronger western Pacific subtropical high (WPSH), and a “lower in the west while higher in the east” geopotential height anomaly in the mid-high latitudes of Eurasia. Therefore, for Henan Province, the extremity of absent sunshine is more obvious. The results of the synthesis of all events from 1981 to 2022 show that the large-scale atmospheric circulation pattern that causes the “wheat-soaked persistent rainfall” event is that the WPSH is westward stronger and the its western ridge line is northward, while the middle and high latitudes of Eurasia are under the “low in the west and high in the east” circulation pattern. In contrast, the circulation pattern of the “wheat-soaked persistent rainfall” event in late May 2023 is similar to that of the historical events in the mid-high latitudes. However, in tropical regions, affected by the Super Typhoon Mawar, the western section of the WPSH is squeezed and deformed, and the moisture transport by the southwesterly wind in the northwest side of the WPSH is significantly much stronger. At the same time, because “Mawar” remain stable near the east of the Philippines for a long time, the southeast wind flow guide by the northeast side of the typhoon is stronger than the southwest wind anomaly on the northwest side of the subtropical high. The two branches of water vapor superpose, leading to persistent precipitation and long-time absence of sunshine in the Huang-Huai-Hai Plain.
2023, 49(10):1235-1245.
DOI: 10.7519/j.issn.1000-0526.2023.021502
Abstract:
The accuracies of microwave radiometer （MWR） measurements obtained at Baoshan Station of Shanghai from July 2018 to July 2019 are evaluated by comparing brightness temperature of MWR against those calculated from radiosonde soundings at the same site with radiative transfer model. Beyond that, the performances of the MWR calibration techniques and the effects of radome replacement are estimated. The results show that the observed brightness temperature from MWR agrees well with the simulated ones from radiosonde soundings in clear-sky conditions. The correlation coefficients between the two datasets are over 0.96 in all channels, with root mean square errors being 0.15-2.68 K. The performances of the V-band channels are better than those of K-band channels. Moreover, the features of brightness temperature bias vary with channels, including random deviations, systematic biases and biases with significant seasonal variations. The absolute calibration with liquid Nitrogen （LN2 calibration） could significantly reduce the systematic bias in most of K-band channels. But the brightness temperature from V-band channels do not change obviously after calibration. By replacing the radome periodically, brightness temperature biases in rainy conditions might be reduced significantly. And the recovery time of brightness temperature in rainy conditions might also be shortened. The results also indicate that the radome made of new material used in this study is more efficient than the original one in reducing the negative impacts of precipitation in MWR accuracy. It works for about 4 months.
The accuracies of microwave radiometer （MWR） measurements obtained at Baoshan Station of Shanghai from July 2018 to July 2019 are evaluated by comparing brightness temperature of MWR against those calculated from radiosonde soundings at the same site with radiative transfer model. Beyond that, the performances of the MWR calibration techniques and the effects of radome replacement are estimated. The results show that the observed brightness temperature from MWR agrees well with the simulated ones from radiosonde soundings in clear-sky conditions. The correlation coefficients between the two datasets are over 0.96 in all channels, with root mean square errors being 0.15-2.68 K. The performances of the V-band channels are better than those of K-band channels. Moreover, the features of brightness temperature bias vary with channels, including random deviations, systematic biases and biases with significant seasonal variations. The absolute calibration with liquid Nitrogen （LN2 calibration） could significantly reduce the systematic bias in most of K-band channels. But the brightness temperature from V-band channels do not change obviously after calibration. By replacing the radome periodically, brightness temperature biases in rainy conditions might be reduced significantly. And the recovery time of brightness temperature in rainy conditions might also be shortened. The results also indicate that the radome made of new material used in this study is more efficient than the original one in reducing the negative impacts of precipitation in MWR accuracy. It works for about 4 months.
2023, 49(10):1246-1253.
DOI: 10.7519/j.issn.1000-0526.2023.080301
Abstract:
Radar networking method is one of the most important methods in Severe Weather Automatic Nowcasting （SWAN） radar applications. Improving the efficiency of the radar networking method can improve the timeliness of the shortterm algorithm sequence, and also can make good use of highresolution radar data, which has important practical significance. With the development of GPU (graphics processing unit) general computing interface, GPU has also been regarded as a powerful computing resource rather than display device for rendering and images. Therefore, this study proposes a new GPU parallel radar networking method based on CUDA (compute unified device architecture). The method is designed in a hybrid architecture of CPU (central processing unit) and GPU, in which the CPU is for the decoding of radar data and scheduling the GPU parallel modules, and the GPU is for the parallel computing of largescale data. By analyzing the parallel overhead of the CUDA and the characteristics of the radar networking method, a scheme of GPU memory management optimization and data exchange process simplification is proposed and implemented, which effectively improves the efficiency of the method. The comparative test results show that, compared with the CPU parallel algorithm in SWAN, the GPU parallel networking method based on CUDA achieves a speedup ratio of 3.52 and 6.82, respectively, on the national puzzle tasks of 1 km and 500 m resolution. To sum up, the parallel networking method based on CUDA can not only improve the timeliness of the shortterm nowcasting methods sequence, but also provide technical support for the puzzle of higher resolution radar data.
Radar networking method is one of the most important methods in Severe Weather Automatic Nowcasting （SWAN） radar applications. Improving the efficiency of the radar networking method can improve the timeliness of the shortterm algorithm sequence, and also can make good use of highresolution radar data, which has important practical significance. With the development of GPU (graphics processing unit) general computing interface, GPU has also been regarded as a powerful computing resource rather than display device for rendering and images. Therefore, this study proposes a new GPU parallel radar networking method based on CUDA (compute unified device architecture). The method is designed in a hybrid architecture of CPU (central processing unit) and GPU, in which the CPU is for the decoding of radar data and scheduling the GPU parallel modules, and the GPU is for the parallel computing of largescale data. By analyzing the parallel overhead of the CUDA and the characteristics of the radar networking method, a scheme of GPU memory management optimization and data exchange process simplification is proposed and implemented, which effectively improves the efficiency of the method. The comparative test results show that, compared with the CPU parallel algorithm in SWAN, the GPU parallel networking method based on CUDA achieves a speedup ratio of 3.52 and 6.82, respectively, on the national puzzle tasks of 1 km and 500 m resolution. To sum up, the parallel networking method based on CUDA can not only improve the timeliness of the shortterm nowcasting methods sequence, but also provide technical support for the puzzle of higher resolution radar data.
2023, 49(10):1254-1266.
DOI: 10.7519/j.issn.1000-0526.2023.080302
Abstract:
Based on the operational real-time typhoon data of National Meteorological Centre and other sources of observations including the ERA-Interim 6 h reanalysis data from the European Centre for Me-dium-Range Weather Forecasting (ECMWF), we analyze and review the main characteristics of typhoon activities in the Northwest Pacific and the South China Sea in 2022. It is found that in 2022, the characteristics of typhoon activity were obvious in stages and clusters with the genesis zones being northward and westward, and the number of typhoons landing in China was still relatively less, which is similar with the typhoon numbers since 2019. However, the typhoon intensities in 2022 were stronger than the average. The forecast error analysis shows that the track errors mainly came from the initial stage of typhoon generation, the combination of typhoon and westerlies, and the period of multiply typhoons or low pressure area activity. Further analysis of the forecast difficulties of the typhoons Chaba, Muifa and Hinnamnor reveals that the continental high and upper-level jet in the north of Chaba at the early stage of its generation was the key system leading to the long-time track adjustment of Chaba. The track errors of the Muifa after landfall were due to the deviation of the models’ forecasts of the steering flows. The track and intensity of Hinnamnor were complex, and China Meteorological Administration (CMA) made forecast deviations in the rate of its rapid intensifying and weakening, intensity fluctuations because of its unexpected changes in structure and size.
Based on the operational real-time typhoon data of National Meteorological Centre and other sources of observations including the ERA-Interim 6 h reanalysis data from the European Centre for Me-dium-Range Weather Forecasting (ECMWF), we analyze and review the main characteristics of typhoon activities in the Northwest Pacific and the South China Sea in 2022. It is found that in 2022, the characteristics of typhoon activity were obvious in stages and clusters with the genesis zones being northward and westward, and the number of typhoons landing in China was still relatively less, which is similar with the typhoon numbers since 2019. However, the typhoon intensities in 2022 were stronger than the average. The forecast error analysis shows that the track errors mainly came from the initial stage of typhoon generation, the combination of typhoon and westerlies, and the period of multiply typhoons or low pressure area activity. Further analysis of the forecast difficulties of the typhoons Chaba, Muifa and Hinnamnor reveals that the continental high and upper-level jet in the north of Chaba at the early stage of its generation was the key system leading to the long-time track adjustment of Chaba. The track errors of the Muifa after landfall were due to the deviation of the models’ forecasts of the steering flows. The track and intensity of Hinnamnor were complex, and China Meteorological Administration (CMA) made forecast deviations in the rate of its rapid intensifying and weakening, intensity fluctuations because of its unexpected changes in structure and size.
2023, 49(10):1267-1276.
DOI: 10.7519/j.issn.1000-0526.2023.072001
Abstract:
In the springtime (March to May, MAM) of 2023, the mean temperature in China was 11.5℃, the seventh highest in history since 1961. The temperature in most of China was higher than normal except that in Xinjiang, the western part of Northwest China and Tibet was lower than normal. The national average precipitation was 132.7 mm, which is 7.4% less than normal. The precipitation showed a feature of “more in the north and less in the south”, with more precipitation in North China, Huanghuai Region and QinghaiTibeteau Plateau but significantly less in Northeast China, the eastern part of the region south the Yangtze River, South China, and Southwest China. In the spring (MAM) of 2023, a “two ridges and one trough” circulation was found to be distributed in the middle and high latitudes of Eurasia. In the middle troposphere, the positive height anomaly center was at the Ural Mountains area, the negative height anomaly center was from the Lake Baikal to Lake Balkhash area, and the 〖JP2〗geopotential height field was posi〖JP〗tive anomaly over Northeast Asia. The western Pacific subtropical high was weaker than normal. In the lower troposphere, an abnormal cyclonic circulation maintained in the tropical western Pacific, while in its north there was an abnormal anticyclone circulation. The high ridge index in Northeast Asia in MAM 2023 was 1.7, exceeding one standard deviation. It is the fourth highest index since 1961, and is favorable for more precipitation in northern China. Affected by the anticyclone circulation, the area to the north of the Yangtze River had an abnormally strong southeasterly wind, which was conducive to the transport of the warm and wet water vapor from the Northwest Pacific to the northern region of China. A weak La Ni〖AKn~D〗a event began in September 2021 in the equatorial central and eastern Pacific and lasted until March 2023. In April 2023, the sea surface temperature (SST) in the equatorial central and eastern Pacific began to shift to a warmer phase. In MAM 2023, precipitation in northern China was affected by the evolution of SST in the equatorial Pacific. The composite analysis showed that in the spring when the SST changed from cold to warm, the circulation anomaly of “two ridges and one trough” was prone to appear in the midlatitude region of Eurasia, and the cold air blowed southward influencing China. Meanwhile, the anticyclone anomaly was found over East Asia, making the southeast wind anomaly prevail in northern China, and more water vapor was transported from the Northwest Pacific to northern China, providing favorable conditions for more precipitation in the region.
In the springtime (March to May, MAM) of 2023, the mean temperature in China was 11.5℃, the seventh highest in history since 1961. The temperature in most of China was higher than normal except that in Xinjiang, the western part of Northwest China and Tibet was lower than normal. The national average precipitation was 132.7 mm, which is 7.4% less than normal. The precipitation showed a feature of “more in the north and less in the south”, with more precipitation in North China, Huanghuai Region and QinghaiTibeteau Plateau but significantly less in Northeast China, the eastern part of the region south the Yangtze River, South China, and Southwest China. In the spring (MAM) of 2023, a “two ridges and one trough” circulation was found to be distributed in the middle and high latitudes of Eurasia. In the middle troposphere, the positive height anomaly center was at the Ural Mountains area, the negative height anomaly center was from the Lake Baikal to Lake Balkhash area, and the 〖JP2〗geopotential height field was posi〖JP〗tive anomaly over Northeast Asia. The western Pacific subtropical high was weaker than normal. In the lower troposphere, an abnormal cyclonic circulation maintained in the tropical western Pacific, while in its north there was an abnormal anticyclone circulation. The high ridge index in Northeast Asia in MAM 2023 was 1.7, exceeding one standard deviation. It is the fourth highest index since 1961, and is favorable for more precipitation in northern China. Affected by the anticyclone circulation, the area to the north of the Yangtze River had an abnormally strong southeasterly wind, which was conducive to the transport of the warm and wet water vapor from the Northwest Pacific to the northern region of China. A weak La Ni〖AKn~D〗a event began in September 2021 in the equatorial central and eastern Pacific and lasted until March 2023. In April 2023, the sea surface temperature (SST) in the equatorial central and eastern Pacific began to shift to a warmer phase. In MAM 2023, precipitation in northern China was affected by the evolution of SST in the equatorial Pacific. The composite analysis showed that in the spring when the SST changed from cold to warm, the circulation anomaly of “two ridges and one trough” was prone to appear in the midlatitude region of Eurasia, and the cold air blowed southward influencing China. Meanwhile, the anticyclone anomaly was found over East Asia, making the southeast wind anomaly prevail in northern China, and more water vapor was transported from the Northwest Pacific to northern China, providing favorable conditions for more precipitation in the region.
2023, 49(10):1277-1284.
DOI: 10.7519/j.issn.1000-0526.2023.091301
Abstract:
The main characteristics of the atmospheric circulation in July 2023 are shown as follows. The polar vortex split into multiple centers distributed around the pole in the Northern Hemisphere, stronger than normal. Compared to the normal, the western Pacific subtropical high was stronger with the position further westward and northward. The monthly mean precipitation across China in July was 122.0 mm, close to the normal. There were 45 stations where the daily precipitation broke the historical records. The positive anomaly of precipitation was significantly 1 to 2 times more than that in western part of Jilin and southern part of Hebei in the same period of a year. However, the negative anomaly of rainfall was 50% less in the northern and central parts of Northwest China, the northern and central parts of Guangxi, the central part of Hunan and the northern part of Xinjiang. There were eight regional rainstorm processes in this month. Influenced by Typhoon Doksuri and the residual circulations, extremely severe rainfall occurred in Taiwan, eastern Zhejiang, eastern Fujian and the BeijingTianjinHebei Region from 26 to 29 July and from 29 July to August 1 in order. Three tropical cyclones were generated in the South China Sea and the western North Pacific, two of which made landfall in China. Generally, the number of landfall typhoons in the July China was less than in the previous years. Typhoon Doksuri was the second strongest typhoon that landed in Fujian. The monthly mean temperature in China was 23.0℃, which was slightly higher than the usual. The mean maximum temperature in western Shandong, southern Hebei, and northwestern and northeastern Xinjiang was 2-4℃ higher than normal. Totally, there were seven high temperature processes in this month. A largescale persistent high temperature weather heated China form 5 to 16 July. The maximum temperature exceeded 35℃ in the most of the central and eastern China, western Inner Mongolia and Xinjiang, and the daily maximum temperature at 12 national stations surpassed the historical extremes.
The main characteristics of the atmospheric circulation in July 2023 are shown as follows. The polar vortex split into multiple centers distributed around the pole in the Northern Hemisphere, stronger than normal. Compared to the normal, the western Pacific subtropical high was stronger with the position further westward and northward. The monthly mean precipitation across China in July was 122.0 mm, close to the normal. There were 45 stations where the daily precipitation broke the historical records. The positive anomaly of precipitation was significantly 1 to 2 times more than that in western part of Jilin and southern part of Hebei in the same period of a year. However, the negative anomaly of rainfall was 50% less in the northern and central parts of Northwest China, the northern and central parts of Guangxi, the central part of Hunan and the northern part of Xinjiang. There were eight regional rainstorm processes in this month. Influenced by Typhoon Doksuri and the residual circulations, extremely severe rainfall occurred in Taiwan, eastern Zhejiang, eastern Fujian and the BeijingTianjinHebei Region from 26 to 29 July and from 29 July to August 1 in order. Three tropical cyclones were generated in the South China Sea and the western North Pacific, two of which made landfall in China. Generally, the number of landfall typhoons in the July China was less than in the previous years. Typhoon Doksuri was the second strongest typhoon that landed in Fujian. The monthly mean temperature in China was 23.0℃, which was slightly higher than the usual. The mean maximum temperature in western Shandong, southern Hebei, and northwestern and northeastern Xinjiang was 2-4℃ higher than normal. Totally, there were seven high temperature processes in this month. A largescale persistent high temperature weather heated China form 5 to 16 July. The maximum temperature exceeded 35℃ in the most of the central and eastern China, western Inner Mongolia and Xinjiang, and the daily maximum temperature at 12 national stations surpassed the historical extremes.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P