Volume 49,Issue 4,2021 Table of Contents
2021, 49(4):509-516.
Abstract:
In the economically developed coastal regions and the big island area, there occurs frequently a variety of weather disasters associated with typhoons, heavy fogs and severe convection. Collection of marine meteorological data in real time is essential for improving the model prediction and thus weather services in the marine and coastal areas. To achieve autonomous system deployment and automatic measurement of marine meteorological parameters, a marine meteorological observation technique has been developed based on a solarpowered unmanned marine vehicle (UMV) and is named the Marine Weather Observer (MWO). A detailed description of this technique and its preliminary results of one experimental case during 1-6, April 2018 are presented in this paper.
In the economically developed coastal regions and the big island area, there occurs frequently a variety of weather disasters associated with typhoons, heavy fogs and severe convection. Collection of marine meteorological data in real time is essential for improving the model prediction and thus weather services in the marine and coastal areas. To achieve autonomous system deployment and automatic measurement of marine meteorological parameters, a marine meteorological observation technique has been developed based on a solarpowered unmanned marine vehicle (UMV) and is named the Marine Weather Observer (MWO). A detailed description of this technique and its preliminary results of one experimental case during 1-6, April 2018 are presented in this paper.
2021, 49(4):517-523.
Abstract:
At present, the next generation weather radar in China is upgrading to the dual polarization system. The accurate measurement of differential reflectivity (〖WTBX〗Z〖WTBZ〗DR) of meteorological targets by the CINRAD/SAD dual polarization weather radar is an important part of parameter calibration. For Xuzhou dual polarization radar, 〖WTBX〗Z〖WTBZ〗DR calibration test for Xuzhou radar was carried out with UAV (Unmanned Aerial Vehicle) carrying two kinds of standard metal spheres, respectively. In this test, the VCPsect scanning mode was configured, the fan scanning combination of target azimuth ±5° was adopted and all radar filtering algorithms such as ground objects were turned off. The results show that the average value of 〖WTBX〗Z〖WTBZ〗DR was 0.265 dB, the minimum was -0.125 dB and the maximum was -0.375 dB, when the 40 cm metal sphere was used, and the distance between UAV and metal sphere was 68 m. The values of ZDR meet the technical requirements of radar 〖WTBX〗Z〖WTBZ〗DR calibration. The research provides a technical solution for operational radar to carry out dual polarization radar 〖WTBX〗Z〖WTBZ〗DR calibration.
At present, the next generation weather radar in China is upgrading to the dual polarization system. The accurate measurement of differential reflectivity (〖WTBX〗Z〖WTBZ〗DR) of meteorological targets by the CINRAD/SAD dual polarization weather radar is an important part of parameter calibration. For Xuzhou dual polarization radar, 〖WTBX〗Z〖WTBZ〗DR calibration test for Xuzhou radar was carried out with UAV (Unmanned Aerial Vehicle) carrying two kinds of standard metal spheres, respectively. In this test, the VCPsect scanning mode was configured, the fan scanning combination of target azimuth ±5° was adopted and all radar filtering algorithms such as ground objects were turned off. The results show that the average value of 〖WTBX〗Z〖WTBZ〗DR was 0.265 dB, the minimum was -0.125 dB and the maximum was -0.375 dB, when the 40 cm metal sphere was used, and the distance between UAV and metal sphere was 68 m. The values of ZDR meet the technical requirements of radar 〖WTBX〗Z〖WTBZ〗DR calibration. The research provides a technical solution for operational radar to carry out dual polarization radar 〖WTBX〗Z〖WTBZ〗DR calibration.
2021, 49(4):524-528.
Abstract:
Based on the GB/T24559 marine propeller anemometer test methods and test points, the propeller anemometer was tested in the lowspeed wind tunnel. According to the JJF1059.12012 measurement uncertainty evaluation and expression requirements, seven calibration points of wind speed were tested repeatedly, and the range method was used to evaluate the type A uncertainty. The sources of type B uncertainty in the testing process are analyzed and the type B uncertainty is evaluated. The results show that it is feasible to calibrate the propeller anemometer in the WZ860070E wind tunnel. At the same time, each test point above 2 m/s can meet the three times of the quantitative transmission relationship.
Based on the GB/T24559 marine propeller anemometer test methods and test points, the propeller anemometer was tested in the lowspeed wind tunnel. According to the JJF1059.12012 measurement uncertainty evaluation and expression requirements, seven calibration points of wind speed were tested repeatedly, and the range method was used to evaluate the type A uncertainty. The sources of type B uncertainty in the testing process are analyzed and the type B uncertainty is evaluated. The results show that it is feasible to calibrate the propeller anemometer in the WZ860070E wind tunnel. At the same time, each test point above 2 m/s can meet the three times of the quantitative transmission relationship.
2021, 49(4):529-534.
Abstract:
Aiming at the phenomenon that the online detection device for battery power in meteorological observation equipment is almost blank, the battery AC injection method detection, Internet of Things (IoT) and other technologies are comprehensively used to inject AC crosscurrent signals at both ends of the battery, and the battery power is calculated by the phase angle and internal resistance of the battery. Experiments and improvements are made of the detection process in practical applications; the Kalman filtering is added to reduce interference; and the reliable direct online measurement of battery power is achieved. According to this method, the specific realization of the hardware circuit is given, which has been applied in actual operation and has high operability, accuracy and consistency.
Aiming at the phenomenon that the online detection device for battery power in meteorological observation equipment is almost blank, the battery AC injection method detection, Internet of Things (IoT) and other technologies are comprehensively used to inject AC crosscurrent signals at both ends of the battery, and the battery power is calculated by the phase angle and internal resistance of the battery. Experiments and improvements are made of the detection process in practical applications; the Kalman filtering is added to reduce interference; and the reliable direct online measurement of battery power is achieved. According to this method, the specific realization of the hardware circuit is given, which has been applied in actual operation and has high operability, accuracy and consistency.
2021, 49(4):535-541.
Abstract:
Meteorological numerical models are the core component of meteorological science and technology innovation, and have become one of the important symbols of technical development progress of meteorological departments. Unlike software products in general, the development of meteorological numerical models is a scientific exploration process and requires strict technical means to ensure operational running. Due to multiple requirements of scientific research experiment, operation management and researchoperation transformation, the continuous improvement process management and code version control are crucially important to the sustainable development of meteorological numerical models. With the development and improvement of meteorological numerical models, it has been widely used in national and regional centers by the geographically dispersed research and development personnel. The development trend of heterogeneous multicore can be seen in the field of highperformance computing, and the interdisciplinary derivation of model research and development becomes more obvious, so the efficient collaborative sharing of distributed model research and development efforts becomes a key problem. In this paper, the METCODE platform is established based on the Git version control system which provides code management and collaboration services. The platform realizes code version management, integrated collaborative sharing and process management of meteorological numerical models, and supports the cooperative research and development of distributed teams conveniently. The platform has been successfully applied in the research and development of the GRAPES model with good results.
Meteorological numerical models are the core component of meteorological science and technology innovation, and have become one of the important symbols of technical development progress of meteorological departments. Unlike software products in general, the development of meteorological numerical models is a scientific exploration process and requires strict technical means to ensure operational running. Due to multiple requirements of scientific research experiment, operation management and researchoperation transformation, the continuous improvement process management and code version control are crucially important to the sustainable development of meteorological numerical models. With the development and improvement of meteorological numerical models, it has been widely used in national and regional centers by the geographically dispersed research and development personnel. The development trend of heterogeneous multicore can be seen in the field of highperformance computing, and the interdisciplinary derivation of model research and development becomes more obvious, so the efficient collaborative sharing of distributed model research and development efforts becomes a key problem. In this paper, the METCODE platform is established based on the Git version control system which provides code management and collaboration services. The platform realizes code version management, integrated collaborative sharing and process management of meteorological numerical models, and supports the cooperative research and development of distributed teams conveniently. The platform has been successfully applied in the research and development of the GRAPES model with good results.
2021, 49(4):542-551.
Abstract:
Based on the GRAPESGlobal Ensemble Forecast System (GRAPESGEPS), and the nationwide coldwave process from 13 to 16 February 2020, the Kmeans cluster products are developed. In this paper, the Sum of the Squared Errors (SSE) criterion function is applied to determine the most appropriate clustering numbers and the Kmeans cluster algorithm is used to classify the ensemble samples. Results indicate that, all types of Kmeans cluster products related to the 500 hPa geopotential height present the Ωshaped circulation situation and the cold advection situation behind the lowpressure system. In addition, Type 1 clustering products with the highest probability reflect the observed circulation situation most efficiently. For 850 hPa temperature, all categories can present the spatial characteristics of 850 hPa temperature, which increase gradually from North China to South China. In addition, Type 1 clustering products with the highest probability can reflect the spatial distribution of 850 hPa temperature and possess the least errors related to the observation. For 10 m wind speed clustering products, at higher wind speeds, the dispersion of the aggregate samples is larger, and the wind speeds of different kinds have significant differences. The Type 1 clustering products with the highest probability can reflect the spatial distribution and intensity of 10 m wind speed in Tianjin and its surrounding areas exactly and provide valuable prediction information for forecasters. With Kmeans cluster results, we can realize the aggregation of forecast sample information and provide the intuitive guidance of weather prediction for the forecasters.
Based on the GRAPESGlobal Ensemble Forecast System (GRAPESGEPS), and the nationwide coldwave process from 13 to 16 February 2020, the Kmeans cluster products are developed. In this paper, the Sum of the Squared Errors (SSE) criterion function is applied to determine the most appropriate clustering numbers and the Kmeans cluster algorithm is used to classify the ensemble samples. Results indicate that, all types of Kmeans cluster products related to the 500 hPa geopotential height present the Ωshaped circulation situation and the cold advection situation behind the lowpressure system. In addition, Type 1 clustering products with the highest probability reflect the observed circulation situation most efficiently. For 850 hPa temperature, all categories can present the spatial characteristics of 850 hPa temperature, which increase gradually from North China to South China. In addition, Type 1 clustering products with the highest probability can reflect the spatial distribution of 850 hPa temperature and possess the least errors related to the observation. For 10 m wind speed clustering products, at higher wind speeds, the dispersion of the aggregate samples is larger, and the wind speeds of different kinds have significant differences. The Type 1 clustering products with the highest probability can reflect the spatial distribution and intensity of 10 m wind speed in Tianjin and its surrounding areas exactly and provide valuable prediction information for forecasters. With Kmeans cluster results, we can realize the aggregation of forecast sample information and provide the intuitive guidance of weather prediction for the forecasters.
2021, 49(4):552-560.
Abstract:
In order to obtain an objective spatial distribution map of diurnal rainfall variation, this study uses the Kmeans clustering algorithm to mine hourly gridded rainfall data over China. Firstly, a large enough number is used to cluster the hourly precipitation at each pixel. Then, according to the peak time of diurnal rainfall variation, the clusters with similar peak time are merged. Each merged cluster corresponds to one type of diurnal rainfall variation, and the locations of grid cells in each cluster form the map of diurnal rainfall variation over China. The results indicate that the characteristic of diurnal variation of rainfall amount is dominated by the diurnal variation of rainfall frequency. In addition, the regions prevailing nocturnal rainfall present a spatial pattern ranged from west to east, and the peak times of the nocturnal rainfall regions show a timedelay propagation from west to east. Taking an overlay analysis between the regions prevailing nocturnal rainfall and terrain, the spatial pattern of the regions prevailing nocturnal rainfall can be well explained by the propagation of the rain belt driven by the MPS (MountainPlain Solenoid) circulation. Overall, the results of this paper can provide clues for the mechanism study of diurnal rainfall variation and also provide a reference for studying the spatial distribution of diurnal rainfall variations in other regions.
In order to obtain an objective spatial distribution map of diurnal rainfall variation, this study uses the Kmeans clustering algorithm to mine hourly gridded rainfall data over China. Firstly, a large enough number is used to cluster the hourly precipitation at each pixel. Then, according to the peak time of diurnal rainfall variation, the clusters with similar peak time are merged. Each merged cluster corresponds to one type of diurnal rainfall variation, and the locations of grid cells in each cluster form the map of diurnal rainfall variation over China. The results indicate that the characteristic of diurnal variation of rainfall amount is dominated by the diurnal variation of rainfall frequency. In addition, the regions prevailing nocturnal rainfall present a spatial pattern ranged from west to east, and the peak times of the nocturnal rainfall regions show a timedelay propagation from west to east. Taking an overlay analysis between the regions prevailing nocturnal rainfall and terrain, the spatial pattern of the regions prevailing nocturnal rainfall can be well explained by the propagation of the rain belt driven by the MPS (MountainPlain Solenoid) circulation. Overall, the results of this paper can provide clues for the mechanism study of diurnal rainfall variation and also provide a reference for studying the spatial distribution of diurnal rainfall variations in other regions.
2021, 49(4):561-568.
Abstract:
Based on the hourly precipitation from the 9 km×9 km resolution SWCWARMS model, ensemble members are formed by the timelagged ensemble forecast method. A new hourly precipitation forecast is obtained from the ensemble average of differential weights, which are calculated by the SAL scores of ensemble members. This study verified the timelagged ensemble and the model uptodate forecast of hourly precipitation in Sichuan from 1 to 31 August 2019 by the SAL, TS and BIAS evaluation method. The results show: (1) The timelagged ensemble method led to improvement on the overall level of the rainfall intensity and location forecast. The values L and A of SAL scores were both closer to 0. (2) The clearrain TS score of timelagged ensemble forecast was higher, and the percentage increase was about 10%. The method can reduce the false alarm of rain forecast. (3) In the lead time of nowcasting, the improvement of the high intensity precipitation forecast was also obvious.
Based on the hourly precipitation from the 9 km×9 km resolution SWCWARMS model, ensemble members are formed by the timelagged ensemble forecast method. A new hourly precipitation forecast is obtained from the ensemble average of differential weights, which are calculated by the SAL scores of ensemble members. This study verified the timelagged ensemble and the model uptodate forecast of hourly precipitation in Sichuan from 1 to 31 August 2019 by the SAL, TS and BIAS evaluation method. The results show: (1) The timelagged ensemble method led to improvement on the overall level of the rainfall intensity and location forecast. The values L and A of SAL scores were both closer to 0. (2) The clearrain TS score of timelagged ensemble forecast was higher, and the percentage increase was about 10%. The method can reduce the false alarm of rain forecast. (3) In the lead time of nowcasting, the improvement of the high intensity precipitation forecast was also obvious.
2021, 49(4):569-578.
Abstract:
Two severe convective weather events (processes “3〖DK〗·21” and “4〖DK〗·9”) in Jiangxi Province in the spring of 2019 are compared and analyzed, by using conventional meteorological observation data. The results show that: (1) Both strong convection processes were formed by the cold air entering the inverted trough. In the “3〖DK〗·21” process, the convergence of cold and warm air was obvious, the temperature trough was ahead of the height trough, and the jet wind speed presented convergence characteristics. During the“4〖DK〗·9” process, the front convergence was weak, and the cold front moved faster. (2) During the “3〖DK〗·21” process, the wet layer was deeper, the high value potential vorticity pool in the upper troposphere extended from top to bottom till 400 hPa, and the “dry invasion” feature was obvious. During the “4〖DK〗·9” process, the overall humidity condition in the middle and lower troposphere was poor, and there was obvious dry air involved in the middle and upper troposphere, while the strong downdraft caused by cooling evaporation caused the ground gale. (3) During the “3〖DK〗·21” process, the bowecho feature was obvious, and the number of mesocyclones was up to 9. The cold air intruded from the height of 3 km and transferred momentum rapidly, and moved faster, which had an indicative significance for the early warning of severe convection such as gales. The invasion of cold air was shallow during the “4〖DK〗·9” event, VIL (Vertical Integrated Liquid water content) of the single storm was small, and strong wind was possibly underestimated by nowcasting warning.
Two severe convective weather events (processes “3〖DK〗·21” and “4〖DK〗·9”) in Jiangxi Province in the spring of 2019 are compared and analyzed, by using conventional meteorological observation data. The results show that: (1) Both strong convection processes were formed by the cold air entering the inverted trough. In the “3〖DK〗·21” process, the convergence of cold and warm air was obvious, the temperature trough was ahead of the height trough, and the jet wind speed presented convergence characteristics. During the“4〖DK〗·9” process, the front convergence was weak, and the cold front moved faster. (2) During the “3〖DK〗·21” process, the wet layer was deeper, the high value potential vorticity pool in the upper troposphere extended from top to bottom till 400 hPa, and the “dry invasion” feature was obvious. During the “4〖DK〗·9” process, the overall humidity condition in the middle and lower troposphere was poor, and there was obvious dry air involved in the middle and upper troposphere, while the strong downdraft caused by cooling evaporation caused the ground gale. (3) During the “3〖DK〗·21” process, the bowecho feature was obvious, and the number of mesocyclones was up to 9. The cold air intruded from the height of 3 km and transferred momentum rapidly, and moved faster, which had an indicative significance for the early warning of severe convection such as gales. The invasion of cold air was shallow during the “4〖DK〗·9” event, VIL (Vertical Integrated Liquid water content) of the single storm was small, and strong wind was possibly underestimated by nowcasting warning.
2021, 49(4):579-588.
Abstract:
Using the Sband dualpolarization Doppler radar in Bengbu, the tornado weather on 22 July 2020 in Suzhou, Anhui Province is analyzed in detail. The results show that under the situation of a rainstorm in the Meiyu period，the lower lifting condensation level and strong vertical wind shear in the middle and low levels provided a favorable environment for the tornado. The tornado occurred in a supercell storm at the southern end of the Meiyu front. There was a hook echo at the right rear of the bottom layer of the supercell. The rapid changes of storm parameters, mesocyclone and TVS (Tornado Vortex Signature) parameters are good indications for early warning and judgement for the occurrence of the tornado. Before the occurrence of the tornado, the maximum reflectivity, vertical accumulated liquid water and top height of the individual storm all increased, while the bottom height decreased significantly. The tornado occurred when the maximum reflectivity factor height dropped rapidly to the bottom. The radar detected the mesocyclone and TVS, 24 and 42 minutes, respectively, before the tornado occurred. Meanwhile the top height of the mesocyclone increased significantly and the maximum hear height dropped sharply. The tornado occurred when the bottom height dropped below 1 km. The top height dropped suddenly and the maximum hear height dropped to the bottom of the mesocyclone. Before the occurrence of tornado, the TVS top height and the maximum shear increased, and the maximum shear height decreased. When the tornado occurred, the top height decreased, and the maximum shear height also decreased to the bottom of TVS. The zerolag correlation coefficient and the tornadic debris signature (TDS) in the low differential reflectance area were observed at the end of the bottom hook echo.
Using the Sband dualpolarization Doppler radar in Bengbu, the tornado weather on 22 July 2020 in Suzhou, Anhui Province is analyzed in detail. The results show that under the situation of a rainstorm in the Meiyu period，the lower lifting condensation level and strong vertical wind shear in the middle and low levels provided a favorable environment for the tornado. The tornado occurred in a supercell storm at the southern end of the Meiyu front. There was a hook echo at the right rear of the bottom layer of the supercell. The rapid changes of storm parameters, mesocyclone and TVS (Tornado Vortex Signature) parameters are good indications for early warning and judgement for the occurrence of the tornado. Before the occurrence of the tornado, the maximum reflectivity, vertical accumulated liquid water and top height of the individual storm all increased, while the bottom height decreased significantly. The tornado occurred when the maximum reflectivity factor height dropped rapidly to the bottom. The radar detected the mesocyclone and TVS, 24 and 42 minutes, respectively, before the tornado occurred. Meanwhile the top height of the mesocyclone increased significantly and the maximum hear height dropped sharply. The tornado occurred when the bottom height dropped below 1 km. The top height dropped suddenly and the maximum hear height dropped to the bottom of the mesocyclone. Before the occurrence of tornado, the TVS top height and the maximum shear increased, and the maximum shear height decreased. When the tornado occurred, the top height decreased, and the maximum shear height also decreased to the bottom of TVS. The zerolag correlation coefficient and the tornadic debris signature (TDS) in the low differential reflectance area were observed at the end of the bottom hook echo.
2021, 49(4):589-596.
Abstract:
In order to study the wind shear characteristics over a plateau airport, this paper uses the data from the Lijiang Airport Automated Weather Observing System (AWOS) and NCEP reanalysis data, as well as 3D data obtained from a wind lidar, to analyze the lowlevel wind shear characteristics of Lijiang Airport on 29 March 2020. The results show that the lowlevel wind shear was mainly formed by the effects of the convergence of the surface isallobaric wind and the enhancement of the turbulence caused by surface warming, as well as the downward momentum transfer. During the occurrence of the wind shear, the lowlevel wind field obtained from the wind lidar was agreed with the surface wind very well. Among the five lowlevel wind shear events, two of them occurred during the orographic wind direction change period from 11:00 to 12:20, and these two are classified as the direction shear of crosswind; the other three occurred from 12:20 to 14:20, which matched with the gradually increasing period of wind speed, and these three are classified as wind speed shear. The wind shear indexes of these five wind shear processes were all greater than 0.1 (1/s), and the shear strengths were moderate or severe, which seriously affected flight safety. The research results provide a reference basis for the laser wind measurement radar monitoring and early warning of airport wind shear.
In order to study the wind shear characteristics over a plateau airport, this paper uses the data from the Lijiang Airport Automated Weather Observing System (AWOS) and NCEP reanalysis data, as well as 3D data obtained from a wind lidar, to analyze the lowlevel wind shear characteristics of Lijiang Airport on 29 March 2020. The results show that the lowlevel wind shear was mainly formed by the effects of the convergence of the surface isallobaric wind and the enhancement of the turbulence caused by surface warming, as well as the downward momentum transfer. During the occurrence of the wind shear, the lowlevel wind field obtained from the wind lidar was agreed with the surface wind very well. Among the five lowlevel wind shear events, two of them occurred during the orographic wind direction change period from 11:00 to 12:20, and these two are classified as the direction shear of crosswind; the other three occurred from 12:20 to 14:20, which matched with the gradually increasing period of wind speed, and these three are classified as wind speed shear. The wind shear indexes of these five wind shear processes were all greater than 0.1 (1/s), and the shear strengths were moderate or severe, which seriously affected flight safety. The research results provide a reference basis for the laser wind measurement radar monitoring and early warning of airport wind shear.
2021, 49(4):597-603.
Abstract:
Based on the observed wind speed data from 1960 to 2019 from 108 ground meteorological stations in Shanxi Province, the trend characteristics of surface wind speeds in Shanxi over the past 60 years are analyzed by the linear fitting, MK test and other methods. The results show that the wind speeds were relatively high in the northwestern and western mountainous areas, the north part of Jinzhong, the southeast part of Changzhi, and the southwest part of Yuncheng Basin, while it was relatively low in the central basin. The wind speed was the highest in spring, followed by winter and summer, and the lowest in autumn. In recent 60 years, the annual and seasonal average wind speeds in Shanxi had obvious change trends and stage characteristics. From the 1960s to the early 1970s, the wind speed increased, and then decreased significantly in the late 1980s. Since the 1990s, the wind speed decreased and slowed down, while the winter wind speed have increased significantly since 1990. The MK test of surface wind speed in Shanxi shows that the abrupt change time of annual, spring, summer, autumn average wind speed was 1982, 1984, 1984 and 1982, respectively, but there was no significant abrupt change in winter average wind speed.
Based on the observed wind speed data from 1960 to 2019 from 108 ground meteorological stations in Shanxi Province, the trend characteristics of surface wind speeds in Shanxi over the past 60 years are analyzed by the linear fitting, MK test and other methods. The results show that the wind speeds were relatively high in the northwestern and western mountainous areas, the north part of Jinzhong, the southeast part of Changzhi, and the southwest part of Yuncheng Basin, while it was relatively low in the central basin. The wind speed was the highest in spring, followed by winter and summer, and the lowest in autumn. In recent 60 years, the annual and seasonal average wind speeds in Shanxi had obvious change trends and stage characteristics. From the 1960s to the early 1970s, the wind speed increased, and then decreased significantly in the late 1980s. Since the 1990s, the wind speed decreased and slowed down, while the winter wind speed have increased significantly since 1990. The MK test of surface wind speed in Shanxi shows that the abrupt change time of annual, spring, summer, autumn average wind speed was 1982, 1984, 1984 and 1982, respectively, but there was no significant abrupt change in winter average wind speed.
2021, 49(4):604-611.
Abstract:
Based on the daily 5cm soil temperature data observed by 97 meteorological stations in Shaanxi Province in 2016, combined with statistical parameters such as correlation coefficient, average deviation and root mean square error, the applicability of CMA (China Meteorological Administration) Land Data Assimilation System (CLDAS 2.0) and American Global Land surface Data Assimilation System (NoahGLDAS 2.1, NoahGLDAS1, CLMGLDAS 1) soil temperature data in Shaanxi Province was evaluated. The results show that: (1) CLDAS 2.0 had the highest correlation coefficient and the smallest rootmeansquare error in Shaanxi Province, followed by NoahGLDAS 2.1 and NoahGLDAS 1. (2) From the analysis of the time evolution series of three regions in Shaanxi Province, it can be seen that CLDAS 2.0 and NoahGLDAS 2.1 can well simulate the seasonal and daily changes of soil temperature, and the simulations of daily changes of NoahGLDAS 1 and CLMGLDAS 1 are poor, and the deviations of the former two are significantly less than those of the latter two. (3) The soil temperature simulation ability of NoahGLDAS 2.1 in the northern Shaanxi and Guanzhong area is similar to that of CLDAS 2.0, but that of CLDAS 2.0 in the southern Shaanxi area is better than that of NoahGLDAS 2.1. Generally speaking, CLDAS 2.0 has the best ability to simulate soil temperature, and has better applicability in Shaanxi Province.
Based on the daily 5cm soil temperature data observed by 97 meteorological stations in Shaanxi Province in 2016, combined with statistical parameters such as correlation coefficient, average deviation and root mean square error, the applicability of CMA (China Meteorological Administration) Land Data Assimilation System (CLDAS 2.0) and American Global Land surface Data Assimilation System (NoahGLDAS 2.1, NoahGLDAS1, CLMGLDAS 1) soil temperature data in Shaanxi Province was evaluated. The results show that: (1) CLDAS 2.0 had the highest correlation coefficient and the smallest rootmeansquare error in Shaanxi Province, followed by NoahGLDAS 2.1 and NoahGLDAS 1. (2) From the analysis of the time evolution series of three regions in Shaanxi Province, it can be seen that CLDAS 2.0 and NoahGLDAS 2.1 can well simulate the seasonal and daily changes of soil temperature, and the simulations of daily changes of NoahGLDAS 1 and CLMGLDAS 1 are poor, and the deviations of the former two are significantly less than those of the latter two. (3) The soil temperature simulation ability of NoahGLDAS 2.1 in the northern Shaanxi and Guanzhong area is similar to that of CLDAS 2.0, but that of CLDAS 2.0 in the southern Shaanxi area is better than that of NoahGLDAS 2.1. Generally speaking, CLDAS 2.0 has the best ability to simulate soil temperature, and has better applicability in Shaanxi Province.
2021, 49(4):612-620.
Abstract:
The DSI (Drought Severity Index) during vegetation growing season in Inner Mongolia from 2000 to 2019 is calculated using MODIS products, and the applicability of DSI in Inner Mongolia is analyzed based on typical drought events and drought indexes such as MCI (Meteorological drought Composite Index) and VCI (Vegetation Condition Index). The results show that the average correlation coefficients of DSI with MCI and VCI are 0.509 and 0.839, passing the significance test of 0.05 and 0.01, respectively, with high consistency. Compared with MCI, DSI has a higher spatial resolution and can reflect the difference in drought resistance of different vegetation types, as well as the enhancement of drought resistance ability after the improvement of regional vegetation. Compared with VCI, DSI is less affected by NDVI saturation in high vegetation coverage areas, and has higher sensitivity in drought relief periods. DSI is suitable for drought monitoring in Inner Mongolia, and can be used in drought monitoring researches and operations.
The DSI (Drought Severity Index) during vegetation growing season in Inner Mongolia from 2000 to 2019 is calculated using MODIS products, and the applicability of DSI in Inner Mongolia is analyzed based on typical drought events and drought indexes such as MCI (Meteorological drought Composite Index) and VCI (Vegetation Condition Index). The results show that the average correlation coefficients of DSI with MCI and VCI are 0.509 and 0.839, passing the significance test of 0.05 and 0.01, respectively, with high consistency. Compared with MCI, DSI has a higher spatial resolution and can reflect the difference in drought resistance of different vegetation types, as well as the enhancement of drought resistance ability after the improvement of regional vegetation. Compared with VCI, DSI is less affected by NDVI saturation in high vegetation coverage areas, and has higher sensitivity in drought relief periods. DSI is suitable for drought monitoring in Inner Mongolia, and can be used in drought monitoring researches and operations.
2021, 49(4):621-628.
Abstract:
Based on the observation data from an artificial precipitation enhancement field experiment, which was carried out on 21 August 2020 in the Qilian Mountains, the characteristics of the raindrop spectrum on the northern slope of the Qilian Mountains and the changes of raindrop spectrum characteristic parameters and spectrum types before and after the precipitation enhancement operation are analyzed. The results show that the precipitation was uneven, but the microphysical parameter eigenvalues of the three observation stations on the northern slope were relatively close. The average raindrop spectral widths were small, and the spectral patterns were basically the same, all of which were unimodal. The peak appeared at about 0.5 mm. The Gamma distribution had a good fitting effect on the raindrop spectrum. The distribution curve can more accurately reflect the distribution of the actual raindrop spectrum, but the fitting value in the peak section (0.5 mm) was biased, and the fitting result was slightly smaller than the measured spectrum. The 〖WTBX〗ZI〖WTBZ〗 relation satisfied the logarithmic correlation; the goodnessoffit 〖WTBX〗R〖WTBZ〗2 was above 0.86; and there was a good fitting relationship. After the operation, the raindrop size, total concentration, rain intensity, etc. all show an increasing trend. After the precipitation enhancement operation, the spectrum width of the raindrop spectrum gradually increased. The peak shape changed from single peak to double peak 10 minutes after the operation. The spectrum width continued to increase 30 minutes and 60 minutes after operation, indicating that the collision process between small raindrops in the cloud began to occur at this time, resulting in largerscale raindrops.
Based on the observation data from an artificial precipitation enhancement field experiment, which was carried out on 21 August 2020 in the Qilian Mountains, the characteristics of the raindrop spectrum on the northern slope of the Qilian Mountains and the changes of raindrop spectrum characteristic parameters and spectrum types before and after the precipitation enhancement operation are analyzed. The results show that the precipitation was uneven, but the microphysical parameter eigenvalues of the three observation stations on the northern slope were relatively close. The average raindrop spectral widths were small, and the spectral patterns were basically the same, all of which were unimodal. The peak appeared at about 0.5 mm. The Gamma distribution had a good fitting effect on the raindrop spectrum. The distribution curve can more accurately reflect the distribution of the actual raindrop spectrum, but the fitting value in the peak section (0.5 mm) was biased, and the fitting result was slightly smaller than the measured spectrum. The 〖WTBX〗ZI〖WTBZ〗 relation satisfied the logarithmic correlation; the goodnessoffit 〖WTBX〗R〖WTBZ〗2 was above 0.86; and there was a good fitting relationship. After the operation, the raindrop size, total concentration, rain intensity, etc. all show an increasing trend. After the precipitation enhancement operation, the spectrum width of the raindrop spectrum gradually increased. The peak shape changed from single peak to double peak 10 minutes after the operation. The spectrum width continued to increase 30 minutes and 60 minutes after operation, indicating that the collision process between small raindrops in the cloud began to occur at this time, resulting in largerscale raindrops.
2021, 49(4):629-636.
Abstract:
The temporal variation of aerosol optical properties retrieved from the Aerosol Robotic Network（AERONET） at the Taihu site in East China is analyzed. The classification study of aerosols is conducted by the method of cluster analysis based on the Mahalanobis distance. The results show that the mean values of aerosol optical depth (AOD) reached a maximum of 1.29 in summer and the maximum value of Angstrom Exponent (AE) is 1.31 in autumn. The highest average value (0.92) of single scattering albedo (SSA) was shown in spring and autumn, while the maximum average value (0.66) of asymmetry factor appeared in summer. The overall seasonal volume size distribution of aerosols showed a bimodal model，with a fine mode peak at about 0.26 μm in summer and a coarse mode peak at about 2.24 μm in spring. The coarse mode aerosols were mainly from the transport of dust aerosols from the north part of China and the marine aerosols from sea. The fine mode aerosols were mainly caused by biomass burning mixed with urban industrial pollutants. The maximum of absorbing aerosol optical depth (AAOD) in summer is 0.11, while the minimum value of AE is 1.0, indicating that aerosol particles in this area contain typical black carbon aerosols. Mixed aerosols accounted for the largest proportion (54.09%) in the Taihu Lake region, followed by urban industrial aerosols (18.95%). Seasonal differences in the proportions of the aerosols of the five categories were more pronounced, and mixed aerosols accounted for the largest proportion in autumn (65.30%). The urban industrial type accounted for the highest proportion in summer (32.07%), and in the spring due to the transport of dusts and aerosol particles in the north, the proportion is the highest (21.01%).
The temporal variation of aerosol optical properties retrieved from the Aerosol Robotic Network（AERONET） at the Taihu site in East China is analyzed. The classification study of aerosols is conducted by the method of cluster analysis based on the Mahalanobis distance. The results show that the mean values of aerosol optical depth (AOD) reached a maximum of 1.29 in summer and the maximum value of Angstrom Exponent (AE) is 1.31 in autumn. The highest average value (0.92) of single scattering albedo (SSA) was shown in spring and autumn, while the maximum average value (0.66) of asymmetry factor appeared in summer. The overall seasonal volume size distribution of aerosols showed a bimodal model，with a fine mode peak at about 0.26 μm in summer and a coarse mode peak at about 2.24 μm in spring. The coarse mode aerosols were mainly from the transport of dust aerosols from the north part of China and the marine aerosols from sea. The fine mode aerosols were mainly caused by biomass burning mixed with urban industrial pollutants. The maximum of absorbing aerosol optical depth (AAOD) in summer is 0.11, while the minimum value of AE is 1.0, indicating that aerosol particles in this area contain typical black carbon aerosols. Mixed aerosols accounted for the largest proportion (54.09%) in the Taihu Lake region, followed by urban industrial aerosols (18.95%). Seasonal differences in the proportions of the aerosols of the five categories were more pronounced, and mixed aerosols accounted for the largest proportion in autumn (65.30%). The urban industrial type accounted for the highest proportion in summer (32.07%), and in the spring due to the transport of dusts and aerosol particles in the north, the proportion is the highest (21.01%).
2021, 49(4):637-646.
Abstract:
Based on the daily power load data in Nanjing from 2014 to 2016, using the harmonic analysis and power spectrum method, etc., the study analyzes the change rule and characteristics of power loads in Nanjing, and the relationship between the daily curve of power load and the meteorological elements such as temperature and humidity in extreme power load days. The results show that the seasonal variation of power loads in Nanjing is mainly bimodal. On the intramonth scale, there is a significant 7days period change, which is significantly corresponding to weekly circulation. There are three types of daily extreme load deviation curves: typical bimodal (Ⅰ), unimodal (Ⅱ), and atypical bimodal (Ⅲ). The typesⅠand Ⅲ show significant positive correlation with temperature and hotness index, while all the three types show significant negative correlation with relative humidity. Then, the type Ⅰcorresponds to the circulation controlled by a strong and stable subhigh over Nanjing, weak cold air activity, and small temperature diurnal variation. The typeⅡ happens while Nanjing is affected by frequent cold air activities and the eastwest swing subtropical high, when showers or thunderstorms usually happen in Nanjing. The intensity of the subtropical high corresponding to type Ⅲ is weaker than that to typeⅠ, and the degree of cold air activity is weaker than that to typeⅡ. The stepwise regression method is adopted to establish prediction models for different types of extreme load days. The average relative errors of the prediction models based on the three types are 6.4%, 5.6%, and 5.3%, respectively, which can provide good quantitative power load forecasts for extreme power load days in Nanjing.
Based on the daily power load data in Nanjing from 2014 to 2016, using the harmonic analysis and power spectrum method, etc., the study analyzes the change rule and characteristics of power loads in Nanjing, and the relationship between the daily curve of power load and the meteorological elements such as temperature and humidity in extreme power load days. The results show that the seasonal variation of power loads in Nanjing is mainly bimodal. On the intramonth scale, there is a significant 7days period change, which is significantly corresponding to weekly circulation. There are three types of daily extreme load deviation curves: typical bimodal (Ⅰ), unimodal (Ⅱ), and atypical bimodal (Ⅲ). The typesⅠand Ⅲ show significant positive correlation with temperature and hotness index, while all the three types show significant negative correlation with relative humidity. Then, the type Ⅰcorresponds to the circulation controlled by a strong and stable subhigh over Nanjing, weak cold air activity, and small temperature diurnal variation. The typeⅡ happens while Nanjing is affected by frequent cold air activities and the eastwest swing subtropical high, when showers or thunderstorms usually happen in Nanjing. The intensity of the subtropical high corresponding to type Ⅲ is weaker than that to typeⅠ, and the degree of cold air activity is weaker than that to typeⅡ. The stepwise regression method is adopted to establish prediction models for different types of extreme load days. The average relative errors of the prediction models based on the three types are 6.4%, 5.6%, and 5.3%, respectively, which can provide good quantitative power load forecasts for extreme power load days in Nanjing.
2021, 49(4):647-653.
Abstract:
Based on the data of thunderstorm days from 1981 to 2010, lightning location from 2012 to 2019, and GDP of the kilometer grid and population in 2015 in Liaoning Province, using the AHP method, risk matrix method and ArcGIS spatial analysis method, the temporal and spatial characteristics of lightning activities in Liaoning Province are analyzed, and the lightning susceptibility level and response level of the 10 km×1 km grid area are obtained. The results indicate that the number of days of lightning activity showed an overall downward trend from 2012 to 2019 in Liaoning Province. Lightning activities mainly occurred from June to September. The maximum total and negative lightning activities appeared in August, and the maximum positive lightning activities appeared in June. The spatial distribution trend of the annual average number of thunderstorm days in Liaoning shows that there were more thunderstorm days in the northern Liaoning than in the southern, and more in the eastern and western Liaoning than in the central part. From the perspective of topography and geomorphology, in the spatial distribution, the numbers of thunderstorm days in mountain areas were greater than those in plains areas, and larger in plains than in coastal areas. The lightningprone areas in Liaoning showed a decreasing distribution trend from the central hills and plains to the eastern and western mountainous areas. The lightningprone areas roughly overlapped with economically developed areas, so attention should be paid.
Based on the data of thunderstorm days from 1981 to 2010, lightning location from 2012 to 2019, and GDP of the kilometer grid and population in 2015 in Liaoning Province, using the AHP method, risk matrix method and ArcGIS spatial analysis method, the temporal and spatial characteristics of lightning activities in Liaoning Province are analyzed, and the lightning susceptibility level and response level of the 10 km×1 km grid area are obtained. The results indicate that the number of days of lightning activity showed an overall downward trend from 2012 to 2019 in Liaoning Province. Lightning activities mainly occurred from June to September. The maximum total and negative lightning activities appeared in August, and the maximum positive lightning activities appeared in June. The spatial distribution trend of the annual average number of thunderstorm days in Liaoning shows that there were more thunderstorm days in the northern Liaoning than in the southern, and more in the eastern and western Liaoning than in the central part. From the perspective of topography and geomorphology, in the spatial distribution, the numbers of thunderstorm days in mountain areas were greater than those in plains areas, and larger in plains than in coastal areas. The lightningprone areas in Liaoning showed a decreasing distribution trend from the central hills and plains to the eastern and western mountainous areas. The lightningprone areas roughly overlapped with economically developed areas, so attention should be paid.
2021, 49(4):654-661.
Abstract:
Based on the observation data of the Zhejiang ADTD lightning location system (from 2007 to 2018), the spatial and temporal distribution characteristics of cloudtoground (CG) lightning are analyzed. Considering both CG lightning density and intensity, an analysis of lightning disaster causing risk is made. The results show that the number of thunderstorm days per year and the percentage of positive CG lightning each year both have a rising tendency during the 12 years. The CG flashes mainly occur from 12:00 to 20:00, June to September. In spring, the proportion of positive CG lightning is much higher, while the most of flashes occur in the evening and at night. In summer, there are many abnormally high values of daily lightning density and lightning area, while the peak hour of daily lightning is mainly in the afternoon. The spatial distribution of higher CG lightning density area varies from west to east with season changes. It is also found that the average CG lightning density over the years is higher in the central Zhejiang than in north and south parts. The amplitude of CG lightning current is mainly distributed from 15 to 45 kA. The average value of CG lightning intensity is the highest in Zhoushan (44.49 kA), while the lowest in Taizhou (32.69 kA). The spatial distribution characteristics of lightning intensity and density are different. It suggests that the very high lightning disastercausing risk level locates in the coastal area of the eastern Zhejiang, HangzhouShaoxing border, northwestern Wenzhou, central Zhejiang and western Zhejiang. The spatial distribution characteristics of disaster causing risk level are consistent with the number of historical lightning disasters as well as the total number of casualties.
Based on the observation data of the Zhejiang ADTD lightning location system (from 2007 to 2018), the spatial and temporal distribution characteristics of cloudtoground (CG) lightning are analyzed. Considering both CG lightning density and intensity, an analysis of lightning disaster causing risk is made. The results show that the number of thunderstorm days per year and the percentage of positive CG lightning each year both have a rising tendency during the 12 years. The CG flashes mainly occur from 12:00 to 20:00, June to September. In spring, the proportion of positive CG lightning is much higher, while the most of flashes occur in the evening and at night. In summer, there are many abnormally high values of daily lightning density and lightning area, while the peak hour of daily lightning is mainly in the afternoon. The spatial distribution of higher CG lightning density area varies from west to east with season changes. It is also found that the average CG lightning density over the years is higher in the central Zhejiang than in north and south parts. The amplitude of CG lightning current is mainly distributed from 15 to 45 kA. The average value of CG lightning intensity is the highest in Zhoushan (44.49 kA), while the lowest in Taizhou (32.69 kA). The spatial distribution characteristics of lightning intensity and density are different. It suggests that the very high lightning disastercausing risk level locates in the coastal area of the eastern Zhejiang, HangzhouShaoxing border, northwestern Wenzhou, central Zhejiang and western Zhejiang. The spatial distribution characteristics of disaster causing risk level are consistent with the number of historical lightning disasters as well as the total number of casualties.
20 Influence Experiment and Analysis of Buried-Metal Conductor on Resistance Test of Grounding Systems
2021, 49(4):662-670.
Abstract:
The influence of a metal conductor in soil on ground resistance is studied by setting up the experimental ground grid. By embedding different shape metal conductors, changing the buried depth of metal conductors and the relative distance from the test grounding grid, the grounding resistance of the test grounding grid was measured at different points. Analysis of test data shows that the buried metal conductor leads to the smaller measured value of grounding resistance, among which the sguareshaped metal conductor has the greatest influence on the measured value of grounding resistance, and the lineshaped metal conductor has the least influence on the measured value. When the metal conductor is located outside the test voltage pole, the influence on the measured value of grounding resistance is greater than that on the inside. When the metal conductor is located inside the test voltage pole, the measured value of grounding resistance at different test points is quite different. When the metal conductor is located outside the test voltage pole, the measured value of grounding resistance at each point has little difference. The buried depth of a metal conductor has no obvious influence on the measured value of grounding resistance.
The influence of a metal conductor in soil on ground resistance is studied by setting up the experimental ground grid. By embedding different shape metal conductors, changing the buried depth of metal conductors and the relative distance from the test grounding grid, the grounding resistance of the test grounding grid was measured at different points. Analysis of test data shows that the buried metal conductor leads to the smaller measured value of grounding resistance, among which the sguareshaped metal conductor has the greatest influence on the measured value of grounding resistance, and the lineshaped metal conductor has the least influence on the measured value. When the metal conductor is located outside the test voltage pole, the influence on the measured value of grounding resistance is greater than that on the inside. When the metal conductor is located inside the test voltage pole, the measured value of grounding resistance at different test points is quite different. When the metal conductor is located outside the test voltage pole, the measured value of grounding resistance at each point has little difference. The buried depth of a metal conductor has no obvious influence on the measured value of grounding resistance.
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.