Volume 47,Issue 6,2019 Table of Contents
2019, 47(6):885-892.
Abstract:
The domestic meteorological communication system CTS (China Telecommunication System) 10 is an important part of CIMISS (China Integrated Meteorological Information Service System), while the data transmission performance of CTS10 is also one of the key indicators for all provincial meteorological departments in weather information services. However, at present, the provincial CTS 1.0 lacks effective backup means, which leads to dangers in its running continuity. In this paper, considering the costeffectiveness and complexity of operation and maintenance, the author proposes a provincial CTS 1.0 backup plan of singlemachine version, and analyzes its system architecture, data flow, basic platform selection and other key contents. In this plan, the process of service switching is elaborately designed to ensure the consistency of service configuration and the uninterrupted monitoring of data flow, and to ensure the service continuity in the process of singlemachine version CTS switching. At the same time, the SSD solidstate hard disk is used to replace the disk array in the infrastructure, which achieves the higher I/O performance of the system and significantly improves the carrying capacity of the standalone version. Through the pressure test and I/O performance analysis of some provincial services, it shows that the plan can provide the reliable support for provincial CTS 1.0 service backup.
The domestic meteorological communication system CTS (China Telecommunication System) 10 is an important part of CIMISS (China Integrated Meteorological Information Service System), while the data transmission performance of CTS10 is also one of the key indicators for all provincial meteorological departments in weather information services. However, at present, the provincial CTS 1.0 lacks effective backup means, which leads to dangers in its running continuity. In this paper, considering the costeffectiveness and complexity of operation and maintenance, the author proposes a provincial CTS 1.0 backup plan of singlemachine version, and analyzes its system architecture, data flow, basic platform selection and other key contents. In this plan, the process of service switching is elaborately designed to ensure the consistency of service configuration and the uninterrupted monitoring of data flow, and to ensure the service continuity in the process of singlemachine version CTS switching. At the same time, the SSD solidstate hard disk is used to replace the disk array in the infrastructure, which achieves the higher I/O performance of the system and significantly improves the carrying capacity of the standalone version. Through the pressure test and I/O performance analysis of some provincial services, it shows that the plan can provide the reliable support for provincial CTS 1.0 service backup.
2019, 47(6):893-899.
Abstract:
Hydrometeorological disasters are one of the major natural disasters affecting China. Hydrometeorological grid data form a dynamic threedimensional flow field. The visualizing flow field is important to explore the inherent variation of hydrometeorological disasters. Considering the data characteristics of large amount, multidimensional, multiscale and dynamic changing, this paper presents a 3D dynamic visualization method for flow fields based on a virtual globe. It includes two data processing methods: flow field data organization and dynamic data interpolation. Meanwhile, three improved visualization techniques including particle tracking, 3D streamline and volume rendering are studied. Finally, the method is verified by two different cases: river flood and typhoon. The experiments show that the method can smoothly realize the detailed dynamic visualization of the threedimensional flow field, which is of great significance for emergency decisionmaking of hydrometeorological disasters.
Hydrometeorological disasters are one of the major natural disasters affecting China. Hydrometeorological grid data form a dynamic threedimensional flow field. The visualizing flow field is important to explore the inherent variation of hydrometeorological disasters. Considering the data characteristics of large amount, multidimensional, multiscale and dynamic changing, this paper presents a 3D dynamic visualization method for flow fields based on a virtual globe. It includes two data processing methods: flow field data organization and dynamic data interpolation. Meanwhile, three improved visualization techniques including particle tracking, 3D streamline and volume rendering are studied. Finally, the method is verified by two different cases: river flood and typhoon. The experiments show that the method can smoothly realize the detailed dynamic visualization of the threedimensional flow field, which is of great significance for emergency decisionmaking of hydrometeorological disasters.
2019, 47(6):900-904.
Abstract:
To solve the problem of low transmission success rate caused by the internal disturbance of 4G and WIFI signals to the downward transmission of Beidou, this paper designs a message transmission project for Automatic Weather Stations (AWSs) based on Beidou to reduce the code error rate by increasing the transmission frequency. It promotes and establishes for the first time the Beidou dualcommander user group for transmitting the messages of AWSs, designs a special encoding format for AWS messages based on the transmission ability of Beidou user machines, and utilizes redundant frequentness to resend the messages that can be repeatedly received for 4 times to guarantee a steady and high transmission success rate. Besides, the AWS messages can be used by forecasters in 1 minute, showing a breakthrough in terms of stability and timeliness.
To solve the problem of low transmission success rate caused by the internal disturbance of 4G and WIFI signals to the downward transmission of Beidou, this paper designs a message transmission project for Automatic Weather Stations (AWSs) based on Beidou to reduce the code error rate by increasing the transmission frequency. It promotes and establishes for the first time the Beidou dualcommander user group for transmitting the messages of AWSs, designs a special encoding format for AWS messages based on the transmission ability of Beidou user machines, and utilizes redundant frequentness to resend the messages that can be repeatedly received for 4 times to guarantee a steady and high transmission success rate. Besides, the AWS messages can be used by forecasters in 1 minute, showing a breakthrough in terms of stability and timeliness.
2019, 47(6):905-911.
Abstract:
Among all kinds of faults of TWP3 wind profiler radar, the failure rate of transmitters is the highest. At present, there is still a lack of a transmitter fault diagnosis method suitable for the technical personnel of radar stations. Based on the working principle and key point signal characteristics of TWP3 wind profile radar transmitters, combined with fault statistics, the common faults of the transmitters are classified into six types of typical faults. By analyzing these typical faults, a method for diagnosing typical faults by means of the flow chart is developed, and three typical cases are analyzed. The results show that this method can diagnose the transmitter faults quickly and accurately. It has the characteristics of clear thinking, standardized operation and being easy to grasp by the technical personnel of radar stations. It can effectively shorten the repair time of transmitter faults and improve the technical support level of TWP3 wind profile radar.
Among all kinds of faults of TWP3 wind profiler radar, the failure rate of transmitters is the highest. At present, there is still a lack of a transmitter fault diagnosis method suitable for the technical personnel of radar stations. Based on the working principle and key point signal characteristics of TWP3 wind profile radar transmitters, combined with fault statistics, the common faults of the transmitters are classified into six types of typical faults. By analyzing these typical faults, a method for diagnosing typical faults by means of the flow chart is developed, and three typical cases are analyzed. The results show that this method can diagnose the transmitter faults quickly and accurately. It has the characteristics of clear thinking, standardized operation and being easy to grasp by the technical personnel of radar stations. It can effectively shorten the repair time of transmitter faults and improve the technical support level of TWP3 wind profile radar.
2019, 47(6):912-915.
Abstract:
Using the domestic pyrheliometer, Finland Milos500 bimetallic sunshine and domestic darktube sunshine recorders at Zhengzhou Meteorological Station and statistical analysis method, the sunshine and observation data from two sets of instruments are compared and analyzed. and the possible causes of the difference are discussed. Results show that the average sunshine duration difference between darktube and Milos500 bimetallic sunshine recorders is 1.6 hours, and that of domestic pyrheliometer and Milos500 bimetallic sunshine recorder is 2.1 hours. Milos500 Bimetallic sunshine recorder observations are much smaller than those of the darktube sunshine recorder and domestic pyrheliometer data, with the difference passing 95% significant level of ttest. The mean value of the difference of sunshine duration observed by the darktube sunshine recorder and the domestic pyrheliometer is 0.2 hours, which is not significant with the best correlation.
Using the domestic pyrheliometer, Finland Milos500 bimetallic sunshine and domestic darktube sunshine recorders at Zhengzhou Meteorological Station and statistical analysis method, the sunshine and observation data from two sets of instruments are compared and analyzed. and the possible causes of the difference are discussed. Results show that the average sunshine duration difference between darktube and Milos500 bimetallic sunshine recorders is 1.6 hours, and that of domestic pyrheliometer and Milos500 bimetallic sunshine recorder is 2.1 hours. Milos500 Bimetallic sunshine recorder observations are much smaller than those of the darktube sunshine recorder and domestic pyrheliometer data, with the difference passing 95% significant level of ttest. The mean value of the difference of sunshine duration observed by the darktube sunshine recorder and the domestic pyrheliometer is 0.2 hours, which is not significant with the best correlation.
2019, 47(6):916-926.
Abstract:
In order to improve the forecasting ability of WRF mode against the gust wind speed, the probability density function matching method (PDF) is used to correct the wind speed errors of wind speed forecasting data from WRF model. The results show that: (1) The gust wind force forecasting based on the PDF method is significantly better than the WRF output. When the observed daily maximum wind speed force ≤ level 5, two forecasting results are both consistent with the observation. When observed daily maximum wind speed force ≥ level 6, comparing with the observed and the wind speed forecasting based on the PDF method, the output from WRF is weaker. (2) By comparing two forecasting results above different topographic conditions, it is found that the effects of the WRF and PDF methods on gust wind in the plain area where the observed wind force is weak are both good. However, in the mountain and valley areas where the observed wind force is strong, the effect of WRF forecast is obviously poor but the effect of the PDF method is improved compared with WRF. (3) By testing forecasting effect on the daily maximum wind speed of 81 national stations in Anhui Province in 2017, it is showed that the forecast error is basically the same as that of the past 5 years, which shows that the probability density distribution function based on the historical data from 2012 to 2016 can represent the joint distribution characteristics of the observed and WRF simulated maximum wind speed from 81 national stations in Anhui Province for many years. So it is reliable by using the PDF method to forecast daily maximum wind speed.
In order to improve the forecasting ability of WRF mode against the gust wind speed, the probability density function matching method (PDF) is used to correct the wind speed errors of wind speed forecasting data from WRF model. The results show that: (1) The gust wind force forecasting based on the PDF method is significantly better than the WRF output. When the observed daily maximum wind speed force ≤ level 5, two forecasting results are both consistent with the observation. When observed daily maximum wind speed force ≥ level 6, comparing with the observed and the wind speed forecasting based on the PDF method, the output from WRF is weaker. (2) By comparing two forecasting results above different topographic conditions, it is found that the effects of the WRF and PDF methods on gust wind in the plain area where the observed wind force is weak are both good. However, in the mountain and valley areas where the observed wind force is strong, the effect of WRF forecast is obviously poor but the effect of the PDF method is improved compared with WRF. (3) By testing forecasting effect on the daily maximum wind speed of 81 national stations in Anhui Province in 2017, it is showed that the forecast error is basically the same as that of the past 5 years, which shows that the probability density distribution function based on the historical data from 2012 to 2016 can represent the joint distribution characteristics of the observed and WRF simulated maximum wind speed from 81 national stations in Anhui Province for many years. So it is reliable by using the PDF method to forecast daily maximum wind speed.
2019, 47(6):927-933.
Abstract:
This paper introduces the application of the optical flow method to the verification and correction of typhoon track forecast. The results show that: (1) By using the optical flow verification method, the prediction error of the geopotential height field can be decomposed into three error fields: intensity, displacement, and angle, and the quantization of the whole error field can be realized. The verification and correction of typhoon track forecast can be carried out by using the displacement and angle error fields. (2) As can be seen from the process of Typhoon Meranti, different numerical models, for the same process, generally behave differently. In the same typhoon process, the forecast deviation of different numerical models can be continuously tracked, and the model with the best forecast stability can be found. Then the displacement and angle errors of this model can be used for typhoon track forecast correction, which is also an effective way to improve the typhoon track forecast accuracy.
This paper introduces the application of the optical flow method to the verification and correction of typhoon track forecast. The results show that: (1) By using the optical flow verification method, the prediction error of the geopotential height field can be decomposed into three error fields: intensity, displacement, and angle, and the quantization of the whole error field can be realized. The verification and correction of typhoon track forecast can be carried out by using the displacement and angle error fields. (2) As can be seen from the process of Typhoon Meranti, different numerical models, for the same process, generally behave differently. In the same typhoon process, the forecast deviation of different numerical models can be continuously tracked, and the model with the best forecast stability can be found. Then the displacement and angle errors of this model can be used for typhoon track forecast correction, which is also an effective way to improve the typhoon track forecast accuracy.
2019, 47(6):934-940.
Abstract:
The decreasing average method and the 10m wind speed gridpoint field analyzed from 28 oil platforms and buoy stations over the Bohai Sea are used to correct the error of the 10 m wind speed forecast in the Bohai area of ROAD model (Regional Ocean and Atmosphere Model). Tests of different weight coefficients indicate: for the forecast field of Bohai 10 mwind speed, the correction is most effective when the weight coefficient is about 0.18.When the lead time is 12 to 72 hours, the monthly hourtohour root mean square error and mean deviation are improved significantly, decreased to 1.0 to 1.5 m/s and 2.3 to 3.0 m/s, respectively. Comparing the representative points of the northern, western and central parts of the Bohai Sea in the lead time of 72 hours, the maximum wind speed scores of every 12 hours turn out: in the lead time of 60 hours, when wind speed forecast is 5 to 6 m/s, most of the forecast scores in the northern, central and western parts of the Bohai Sea are improved. When wind speed forecast is 7 m/s, the maximum wind speed forecast score of the past 12 hours is improved, being 36 to 72 hours and 24 to 48 hour in northern and central parts of the Bohai Sea. The scores are improved most obviously in the range of the wind force distribution with the highest concurrency frequency.
The decreasing average method and the 10m wind speed gridpoint field analyzed from 28 oil platforms and buoy stations over the Bohai Sea are used to correct the error of the 10 m wind speed forecast in the Bohai area of ROAD model (Regional Ocean and Atmosphere Model). Tests of different weight coefficients indicate: for the forecast field of Bohai 10 mwind speed, the correction is most effective when the weight coefficient is about 0.18.When the lead time is 12 to 72 hours, the monthly hourtohour root mean square error and mean deviation are improved significantly, decreased to 1.0 to 1.5 m/s and 2.3 to 3.0 m/s, respectively. Comparing the representative points of the northern, western and central parts of the Bohai Sea in the lead time of 72 hours, the maximum wind speed scores of every 12 hours turn out: in the lead time of 60 hours, when wind speed forecast is 5 to 6 m/s, most of the forecast scores in the northern, central and western parts of the Bohai Sea are improved. When wind speed forecast is 7 m/s, the maximum wind speed forecast score of the past 12 hours is improved, being 36 to 72 hours and 24 to 48 hour in northern and central parts of the Bohai Sea. The scores are improved most obviously in the range of the wind force distribution with the highest concurrency frequency.
2019, 47(6):941-951.
Abstract:
In this paper, based on the data of daily snow depth (SD) and the number of days with snow cover (NDSC) from the National Meteorological Information Center and the atmospheric circulation data from NOAA reanalysis, by using the Empirical Orthogonal Function (EOF) decomposition, composite analysis, and other statistical methods, we examine the interannual and interdecadal variations of winter and spring snows in terms of the number of days with snow cover (NDSC) and snow depth (SD) in the entire Tibetan Plateau, the eastern Tibetan Plateau (ETP), and the western Tibetan Plateau (WTP), respectively, and found that in the past 53 years (1961 to 2013), the temporal trends of winter and spring snows averaged over the entire Tibetan Plateau are general similar. The interdecadal variations of SD exhibit the feature of “lessrichlessrich” than normal,and those of NDSC shows the feature of “lessrichless” than normal. For the temporal trends of snow cover in two regions (ETP and WTP), snows increased significantly in the the 1960s and 1970s and reduced in the 1980s and 1990s for both regions. However, the trends were obviously different since the late 1990s, when the snow cover reduced significantly in the ETP whereas it significantly increased in the WTP except for the spring NDSC that showed no apparent trends. Then we identify the typical years with anomalous snow cover in the ETP and WTP, respectively, and investigate the features of snow cover anomalies and the associated atmospheric circulation anomalies. Finally we investigate the impacts of snow cover anomalies in the Tibetan Plateau on the summer rainfall over China. The results show that significant difference exists in the temporal variations of snow cover for the different regions of the Tibetan Plateau. The results also show apparent correlation between snow cover variations in the Tibetan Plateau and summer rainfall in China. Therefore, it is necessary to take into account the different impacts exerted on summer rainfall by snow cover anomalies in different regions of the Tibetan Plateau when the snow cover in the Tibetan Plateau is used as a factor for the shortterm prediction of summer climate in China.
In this paper, based on the data of daily snow depth (SD) and the number of days with snow cover (NDSC) from the National Meteorological Information Center and the atmospheric circulation data from NOAA reanalysis, by using the Empirical Orthogonal Function (EOF) decomposition, composite analysis, and other statistical methods, we examine the interannual and interdecadal variations of winter and spring snows in terms of the number of days with snow cover (NDSC) and snow depth (SD) in the entire Tibetan Plateau, the eastern Tibetan Plateau (ETP), and the western Tibetan Plateau (WTP), respectively, and found that in the past 53 years (1961 to 2013), the temporal trends of winter and spring snows averaged over the entire Tibetan Plateau are general similar. The interdecadal variations of SD exhibit the feature of “lessrichlessrich” than normal,and those of NDSC shows the feature of “lessrichless” than normal. For the temporal trends of snow cover in two regions (ETP and WTP), snows increased significantly in the the 1960s and 1970s and reduced in the 1980s and 1990s for both regions. However, the trends were obviously different since the late 1990s, when the snow cover reduced significantly in the ETP whereas it significantly increased in the WTP except for the spring NDSC that showed no apparent trends. Then we identify the typical years with anomalous snow cover in the ETP and WTP, respectively, and investigate the features of snow cover anomalies and the associated atmospheric circulation anomalies. Finally we investigate the impacts of snow cover anomalies in the Tibetan Plateau on the summer rainfall over China. The results show that significant difference exists in the temporal variations of snow cover for the different regions of the Tibetan Plateau. The results also show apparent correlation between snow cover variations in the Tibetan Plateau and summer rainfall in China. Therefore, it is necessary to take into account the different impacts exerted on summer rainfall by snow cover anomalies in different regions of the Tibetan Plateau when the snow cover in the Tibetan Plateau is used as a factor for the shortterm prediction of summer climate in China.
2019, 47(6):952-958.
Abstract:
The daily precipitation data of Shanxi Province from 1979 to 2010 and the reanalysis dataset of the European Centre for MediumRange Weather Forecasts are used to explore the relationship between atmospheric lowfrequency oscillations in the Eurasian region and the precipitation weather process of Shanxi Province from April to September by the diagnostic analysis method. The results indicate that the daily precipitation patterns in Shanxi can be mainly divided into three types: provincial consistency, NorthCentral, and Central types. Daily precipitation in Shanxi obviously varies with a characteristic of quasibiweekly cycle. The lowfrequency key region of 500 hPa influencing the precipitation in Shanxi is near the Bohai Sea on the East Coast of China and the lowfrequency influence system is the Bohai Sea lowfrequency high. The Bohai Sea lowfrequency high varies with the quasibiweekly cycle. The index of the Bohai Sea lowfrequency high turns into positive phase 0 to 3 days before the precipitation occurrence in Shanxi. The Bohai Sea lowfrequency high originates from the West Siberian lowfrequency high, which is mainly located in east of West Siberia to west of Central Siberia and propagates to the Bohai Sea about a quasibiweekly cycle.
The daily precipitation data of Shanxi Province from 1979 to 2010 and the reanalysis dataset of the European Centre for MediumRange Weather Forecasts are used to explore the relationship between atmospheric lowfrequency oscillations in the Eurasian region and the precipitation weather process of Shanxi Province from April to September by the diagnostic analysis method. The results indicate that the daily precipitation patterns in Shanxi can be mainly divided into three types: provincial consistency, NorthCentral, and Central types. Daily precipitation in Shanxi obviously varies with a characteristic of quasibiweekly cycle. The lowfrequency key region of 500 hPa influencing the precipitation in Shanxi is near the Bohai Sea on the East Coast of China and the lowfrequency influence system is the Bohai Sea lowfrequency high. The Bohai Sea lowfrequency high varies with the quasibiweekly cycle. The index of the Bohai Sea lowfrequency high turns into positive phase 0 to 3 days before the precipitation occurrence in Shanxi. The Bohai Sea lowfrequency high originates from the West Siberian lowfrequency high, which is mainly located in east of West Siberia to west of Central Siberia and propagates to the Bohai Sea about a quasibiweekly cycle.
2019, 47(6):959-968.
Abstract:
Based on the conventional observational data, satellite images, automatic observational precipitation and NCEP/NCAR reanalysis data (0.25°×0.25°), the characteristics of dynamic and thermal field structure of a rainstorm affected by different systems in the northern part of Northeast China on 24 and 25 July 2018 are analyzed. The major conclusions are as follows: the rainstorm was caused by the warm front frontogenesis, and the rainstorm range was widespread on 24 Jul 2018. There appeared typhoon torrential rain on the typhoon movement path, manifested as a narrow rainfall belt on 25 Jul 2018. The rainstorm was caused by MCS (Mesoscale Convection System) activities, and each shorttime heavy rainfall corresponded to a low value center of TBB. The intensity of MCS in the typhoon trough was weaker than that in the warm front cloud system, but the intensity of precipitation was greater. Typhoon Ampil carried a large amount of warm and wet air, and the lowlevel jet stream on its east side transferred heat and water vapor to the north. The water vapor convergence was in the boundary layer, and the water vapor convergence intensity of the typhoon rainstorm was stronger than that of the warm front rainstorm, resulting in stronger rainfall. During the warm front rainstorm, the convergence and uplift of the windward slope of the Xiaoxingan Mountains were obvious. The highlevel strong divergence and topographic convergence uplift contributed to the rainstorm. During the typhoon and rainstorm, the convergence at low altitudes, especially the convergence of water vapor in the lower layer, made a great contribution to the rainstorm. The convergence zone was located near the typhoon trough, and the typhoon trough had the properties of a cold front.
Based on the conventional observational data, satellite images, automatic observational precipitation and NCEP/NCAR reanalysis data (0.25°×0.25°), the characteristics of dynamic and thermal field structure of a rainstorm affected by different systems in the northern part of Northeast China on 24 and 25 July 2018 are analyzed. The major conclusions are as follows: the rainstorm was caused by the warm front frontogenesis, and the rainstorm range was widespread on 24 Jul 2018. There appeared typhoon torrential rain on the typhoon movement path, manifested as a narrow rainfall belt on 25 Jul 2018. The rainstorm was caused by MCS (Mesoscale Convection System) activities, and each shorttime heavy rainfall corresponded to a low value center of TBB. The intensity of MCS in the typhoon trough was weaker than that in the warm front cloud system, but the intensity of precipitation was greater. Typhoon Ampil carried a large amount of warm and wet air, and the lowlevel jet stream on its east side transferred heat and water vapor to the north. The water vapor convergence was in the boundary layer, and the water vapor convergence intensity of the typhoon rainstorm was stronger than that of the warm front rainstorm, resulting in stronger rainfall. During the warm front rainstorm, the convergence and uplift of the windward slope of the Xiaoxingan Mountains were obvious. The highlevel strong divergence and topographic convergence uplift contributed to the rainstorm. During the typhoon and rainstorm, the convergence at low altitudes, especially the convergence of water vapor in the lower layer, made a great contribution to the rainstorm. The convergence zone was located near the typhoon trough, and the typhoon trough had the properties of a cold front.
2019, 47(6):969-975.
Abstract:
Using the cloud picture data of FY2E satellite, 35 regional rainstorm processes occurred in Meishan of the Sichuan basin during the summers (JuneSeptember) of 2012 to 2018 are analyzed, and the characteristics of convective cloud merging in the rainstorm processes are explored and studied. The statistical results show that convective cloud merging occurs in 88% of rainstorms, and the convective cloud merging is an important factor in the process of severe convective weather. According to the number and time of cloud merging, the processes can be divided into three categories: two monomer convective clouds merged, multiple convective clouds merging simultaneously, and multiple convective clouds merging repeatedly. At the same time, the merging phenomenon in rainstorms is closely related to the distance, area ratio, minimum bright temperature difference, and the average of the minimum bright temperature between the clouds.
Using the cloud picture data of FY2E satellite, 35 regional rainstorm processes occurred in Meishan of the Sichuan basin during the summers (JuneSeptember) of 2012 to 2018 are analyzed, and the characteristics of convective cloud merging in the rainstorm processes are explored and studied. The statistical results show that convective cloud merging occurs in 88% of rainstorms, and the convective cloud merging is an important factor in the process of severe convective weather. According to the number and time of cloud merging, the processes can be divided into three categories: two monomer convective clouds merged, multiple convective clouds merging simultaneously, and multiple convective clouds merging repeatedly. At the same time, the merging phenomenon in rainstorms is closely related to the distance, area ratio, minimum bright temperature difference, and the average of the minimum bright temperature between the clouds.
2019, 47(6):976-985.
Abstract:
Using the conventional ground and upperlevel synoptic charts and radar observation data, the cause of a local severe hail weather process in the Enshi mountain area of Hubei Province on 15 April 2017 is analyzed. The results show that the thermal effect of warm and low pressure systems on the ground before the front strengthened the convergence and the accumulation of the unstable energy on the ground, and made the warm and wet unstable stratification under the dry and cold condition more obvious. Under the action of the dynamic uplift of the mesoscale convergence line, the uplift of the lowlevel convergence triggered the release of convective unstable energy, and coupled with the uplift of the favorable bellshaped terrain of the mountainous area, the development of the severe convective weather was stimulated. In the process of the severe convective weather, the multicell storms had the feature of one’s strengthening companying with the weakening of another. Under the favorable atmospheric environment and terrain conditions, the development of multicell storms was strengthened and the strong storms were maintained for a long time, which were the important reasons for the local strong hail. The vertical structure of hailstorm cell reflects the typical characteristics of the lowlevel inflow, weak echo zone, highstrength echo overhang, etc., and the combined action of the middlelevel radial convergence and the divergence of the storm top made the storm cell maintain and develop, which is also an important cause of the local hailstorm. The monocell storm reflectance factor reflects that it maintained above 60 dBz for a long time and corresponded to a large VIL value. The strong hail weather had the characteristics of strong locality and small impact scope. The main reason is that the vertical wind shear of 0 to 6 kilometers was not large. At the same time, the middle and lowlevel wet layers were shallow, and the wet area on the ground was obviously southward.
Using the conventional ground and upperlevel synoptic charts and radar observation data, the cause of a local severe hail weather process in the Enshi mountain area of Hubei Province on 15 April 2017 is analyzed. The results show that the thermal effect of warm and low pressure systems on the ground before the front strengthened the convergence and the accumulation of the unstable energy on the ground, and made the warm and wet unstable stratification under the dry and cold condition more obvious. Under the action of the dynamic uplift of the mesoscale convergence line, the uplift of the lowlevel convergence triggered the release of convective unstable energy, and coupled with the uplift of the favorable bellshaped terrain of the mountainous area, the development of the severe convective weather was stimulated. In the process of the severe convective weather, the multicell storms had the feature of one’s strengthening companying with the weakening of another. Under the favorable atmospheric environment and terrain conditions, the development of multicell storms was strengthened and the strong storms were maintained for a long time, which were the important reasons for the local strong hail. The vertical structure of hailstorm cell reflects the typical characteristics of the lowlevel inflow, weak echo zone, highstrength echo overhang, etc., and the combined action of the middlelevel radial convergence and the divergence of the storm top made the storm cell maintain and develop, which is also an important cause of the local hailstorm. The monocell storm reflectance factor reflects that it maintained above 60 dBz for a long time and corresponded to a large VIL value. The strong hail weather had the characteristics of strong locality and small impact scope. The main reason is that the vertical wind shear of 0 to 6 kilometers was not large. At the same time, the middle and lowlevel wet layers were shallow, and the wet area on the ground was obviously southward.
2019, 47(6):986-996.
Abstract:
By using the conventional observation data, intensive automatic station data, and the data of NCEP (1°×1°， 4 times per day) and Doppler radar, a local heavy rain occurred in the central Yunnan on 20 June 2017 is analyzed. The results show that the 700 hPa shear line and the ground convergence line were the main weather systems that produced the local torrential rain. The local torrential rain occurred in the weak convection environment where there were lowlevel converges and the middle and upperlevel diverges, and the strong local water vapor convergence in the lower level provided water vapor conditions for the heavy rain. The local torrential rain occurred in the area with the maximum TBB gradient at the edge of the convective cloud cluster. The surface dewpoint temperature increased significantly 6 hours before the storm happens and CAPE also increased significantly. During the heavy rainfall process, there were two rainfall peaks: the first lasted for a long period and mainly caused by the heavy precipitation supercell and mesocyclone; the second lasted for a short period and was weak, mainly caused by multiple convective storms. The Doppler radar charts of the two stages shows the lowcentroid structure, and there was radial velocity formed in the upwind zone, which was about 1 hour ahead of the storm. The precipitation intensity decreased with the disappearance of the upwind zone. The local heavy rain occurred in a terrain, and the heavy rainfall occurred in a valley surrounded by mountains on three sides. The stable and less movement of the convective storm in a bellshaped valley was an important reason for the local torrential rain.
By using the conventional observation data, intensive automatic station data, and the data of NCEP (1°×1°， 4 times per day) and Doppler radar, a local heavy rain occurred in the central Yunnan on 20 June 2017 is analyzed. The results show that the 700 hPa shear line and the ground convergence line were the main weather systems that produced the local torrential rain. The local torrential rain occurred in the weak convection environment where there were lowlevel converges and the middle and upperlevel diverges, and the strong local water vapor convergence in the lower level provided water vapor conditions for the heavy rain. The local torrential rain occurred in the area with the maximum TBB gradient at the edge of the convective cloud cluster. The surface dewpoint temperature increased significantly 6 hours before the storm happens and CAPE also increased significantly. During the heavy rainfall process, there were two rainfall peaks: the first lasted for a long period and mainly caused by the heavy precipitation supercell and mesocyclone; the second lasted for a short period and was weak, mainly caused by multiple convective storms. The Doppler radar charts of the two stages shows the lowcentroid structure, and there was radial velocity formed in the upwind zone, which was about 1 hour ahead of the storm. The precipitation intensity decreased with the disappearance of the upwind zone. The local heavy rain occurred in a terrain, and the heavy rainfall occurred in a valley surrounded by mountains on three sides. The stable and less movement of the convective storm in a bellshaped valley was an important reason for the local torrential rain.
2019, 47(6):997-1005.
Abstract:
Using the data of surface meteorological observation, regional automatic meteorological station observation, radar and satellites, and NCEP 1°×1° 6hour reanalysis, the formation mechanisms of a squall line weather process in the southern part of the Panxi area on 13 May 2018 is analyzed. The highaltitude trough gradually moved eastward to push the cold airflow to the east along the leeward slope, and then merged with the lowlevel warm air in front to form convection. The main trigger factor making the squall line weather process happen was the dewpoint front. The atmosphere around the squall line had the characteristics of dry at upper levels and wet at lower levels, high instability energy, strong vertical wind shear, large highlevel wind speed and the presence of an inversion layer before formation. The upper level jet stream and momentum downward transfer had a positive effect on the occurrence and strengthening of the squall line. The terrain had an effect on the formation of the squall line and the distribution of the weather phenomena.
Using the data of surface meteorological observation, regional automatic meteorological station observation, radar and satellites, and NCEP 1°×1° 6hour reanalysis, the formation mechanisms of a squall line weather process in the southern part of the Panxi area on 13 May 2018 is analyzed. The highaltitude trough gradually moved eastward to push the cold airflow to the east along the leeward slope, and then merged with the lowlevel warm air in front to form convection. The main trigger factor making the squall line weather process happen was the dewpoint front. The atmosphere around the squall line had the characteristics of dry at upper levels and wet at lower levels, high instability energy, strong vertical wind shear, large highlevel wind speed and the presence of an inversion layer before formation. The upper level jet stream and momentum downward transfer had a positive effect on the occurrence and strengthening of the squall line. The terrain had an effect on the formation of the squall line and the distribution of the weather phenomena.
2019, 47(6):1006-1013.
Abstract:
Using the negative oxygen ion data of 53 stations over Zhejiang Province in 2016, a data quality control method for negative oxygen ions is developed. Then negative oxygen ion resources are evaluated from several indexes, including annual mean and maximum values, daily maximum and minimum values, the proportion of concentration in each grade, and fresh degree, the spatial and temporal distribution characteristics and regional differences of negative oxygen ions in the province are analyzed comprehensively. The results show that the content of negative oxygen ions is higher in southern and western mountains of Zhejiang, and that in the northern plain is lower relatively. The concentration of negative oxygen ions has obvious daily and monthly variation characteristics in Zhejiang Province：the concentration is low in the afternoon (13:00 to 16:00) and high in the evening and morning (22:00 to 07:00). The concentration is high from April to September, and low in winter. The monthly change in mountain and forest stations are the most remarkable. The concentration of negative oxygen ions in mountain and forest regions is kept at the fresh level basically. The levels of fresh, general, not fresh is about onethird each over the shallow hill regions. The not clean level is account for half in plain and scenic regions. The average number of fresh air hours in mountain and forest areas is more than 20 per day; very fresh air is also more than 16 hours. In scenic spots, forest areas, water parks of shallow hills and plains, the fresh air is also over 10 hours per day.
Using the negative oxygen ion data of 53 stations over Zhejiang Province in 2016, a data quality control method for negative oxygen ions is developed. Then negative oxygen ion resources are evaluated from several indexes, including annual mean and maximum values, daily maximum and minimum values, the proportion of concentration in each grade, and fresh degree, the spatial and temporal distribution characteristics and regional differences of negative oxygen ions in the province are analyzed comprehensively. The results show that the content of negative oxygen ions is higher in southern and western mountains of Zhejiang, and that in the northern plain is lower relatively. The concentration of negative oxygen ions has obvious daily and monthly variation characteristics in Zhejiang Province：the concentration is low in the afternoon (13:00 to 16:00) and high in the evening and morning (22:00 to 07:00). The concentration is high from April to September, and low in winter. The monthly change in mountain and forest stations are the most remarkable. The concentration of negative oxygen ions in mountain and forest regions is kept at the fresh level basically. The levels of fresh, general, not fresh is about onethird each over the shallow hill regions. The not clean level is account for half in plain and scenic regions. The average number of fresh air hours in mountain and forest areas is more than 20 per day; very fresh air is also more than 16 hours. In scenic spots, forest areas, water parks of shallow hills and plains, the fresh air is also over 10 hours per day.
2019, 47(6):1014-1020.
Abstract:
According to the wind shear events reported by aircrafts at Dali Airport in 2016 and 2017, the wind shear at Dali Airport is analyzed by using the automatic meteorological observation data and wind profiler radar data in relevant periods. The results show that: (1) Wind shear occurs from November to April of the next year, mostly in January and February, mainly in 07:00 to 13:00, half in sunny days, and 83% below 350 m. (2) The wind shear below 100 m has gust winds on the ground, and the maximumminimum difference of wind speeds is more than 6 m/s. Six wind shear events occurred in the range of 15 to 91 m. The wind direction at one end of the five wind shear reports varied by more than 180 degrees. The ground winds at the north and south ends had opposite winds, and the difference of wind speeds was obvious. AWOS (Automated Weather Observation System) captured significant changes in wind direction and velocity, which can provide reference for early warning of nearsurface wind shear. (3) When a wind shear occurs at a high altitude, there is a difference of wind speeds (>8 m/s) between the upper and lower layers of radar data, which can determine the exact height, start time and end time of discontinuous upper and lowerlayer winds. (4) The airport area is often under the situation of large ground wind speed and small upper air wind speed or small ground wind and large upper air wind speed, so the combination of ground wind and wind profiler radar data can provide reference for the preliminary early warning of low altitude wind shear in the future.
According to the wind shear events reported by aircrafts at Dali Airport in 2016 and 2017, the wind shear at Dali Airport is analyzed by using the automatic meteorological observation data and wind profiler radar data in relevant periods. The results show that: (1) Wind shear occurs from November to April of the next year, mostly in January and February, mainly in 07:00 to 13:00, half in sunny days, and 83% below 350 m. (2) The wind shear below 100 m has gust winds on the ground, and the maximumminimum difference of wind speeds is more than 6 m/s. Six wind shear events occurred in the range of 15 to 91 m. The wind direction at one end of the five wind shear reports varied by more than 180 degrees. The ground winds at the north and south ends had opposite winds, and the difference of wind speeds was obvious. AWOS (Automated Weather Observation System) captured significant changes in wind direction and velocity, which can provide reference for early warning of nearsurface wind shear. (3) When a wind shear occurs at a high altitude, there is a difference of wind speeds (>8 m/s) between the upper and lower layers of radar data, which can determine the exact height, start time and end time of discontinuous upper and lowerlayer winds. (4) The airport area is often under the situation of large ground wind speed and small upper air wind speed or small ground wind and large upper air wind speed, so the combination of ground wind and wind profiler radar data can provide reference for the preliminary early warning of low altitude wind shear in the future.
2019, 47(6):1021-1025.
Abstract:
Flooding is one of the most common and serious natural disasters in China. Presently we usually simulate the most severe waterlogging during the rainfall process and lack the simulation technique for the whole rainfall process in the urban waterlogging simulation study. In this study, comprehensively using the SWMM model and GIS technology, by dividing the water catchment areas of the research area and modeling of the generalized drainage network, the SWMM model for the study area is established, and at the same time calculating the amount of water collected in the precipitation process based on the SWMM model, calculating the evolution of surface water by using the active diffusion algorithm. The simulation and simulation error analysis of the precipitation process in the research area on 18 June 2016 show that the method has good simulation effect.
Flooding is one of the most common and serious natural disasters in China. Presently we usually simulate the most severe waterlogging during the rainfall process and lack the simulation technique for the whole rainfall process in the urban waterlogging simulation study. In this study, comprehensively using the SWMM model and GIS technology, by dividing the water catchment areas of the research area and modeling of the generalized drainage network, the SWMM model for the study area is established, and at the same time calculating the amount of water collected in the precipitation process based on the SWMM model, calculating the evolution of surface water by using the active diffusion algorithm. The simulation and simulation error analysis of the precipitation process in the research area on 18 June 2016 show that the method has good simulation effect.
2019, 47(6):1026-1031.
Abstract:
In order to develop and improve the professional lightning earlywarning/nowcasting service products and their timeliness, this paper calculates the distance for each grid between the lightning occurring in the first 5 periods of early warning and the grids on the basis of 6min and 0.01°×0.01° grids, and on the foundation of the lightning nowcasting and early warning model controlled by the radar thresholds. According to the size and changing trend of lightning approaching grid distance, the early warning rules are determined, and the nowcasting warning products of the occurrence of lightning in the grids and key areas in the next 6 minutes are generated. The prediction success rate of the model is evaluated quantitatively and qualitatively. The results show that compared with the traditional method of relying on radar threshold control for lightning nowcasting and early warning, the prediction accuracy of grating and region is improved, and the calculation speed is faster, which can be applied to the practical and especially operational lightning nowcasting and early warning service.
In order to develop and improve the professional lightning earlywarning/nowcasting service products and their timeliness, this paper calculates the distance for each grid between the lightning occurring in the first 5 periods of early warning and the grids on the basis of 6min and 0.01°×0.01° grids, and on the foundation of the lightning nowcasting and early warning model controlled by the radar thresholds. According to the size and changing trend of lightning approaching grid distance, the early warning rules are determined, and the nowcasting warning products of the occurrence of lightning in the grids and key areas in the next 6 minutes are generated. The prediction success rate of the model is evaluated quantitatively and qualitatively. The results show that compared with the traditional method of relying on radar threshold control for lightning nowcasting and early warning, the prediction accuracy of grating and region is improved, and the calculation speed is faster, which can be applied to the practical and especially operational lightning nowcasting and early warning service.
2019, 47(6):1032-1036.
Abstract:
Meteorological forecasting services and meteorological energy development require data with longer time series, higher spatial and temporal resolution, especially for hourly data. Meteorological data scanned from recording papers have problems such as stains, fading, blurring, and smearing, which cannot meet the requirements of archiving and servicing, and also makes the numerical extraction of images greatly difficult, and the accuracy of extraction results is not guaranteed. This paper proposes an image optimization algorithm based on K means, which can quickly identify and distinguish the image background and data recording curves, filter noise in images, and unify the color and thickness of data recording curves. After optimization, the contrast and sharpness of the images are obviously increased, and the volume is obviously reduced. In practice, it is found that the optimized images save storage resources and cost, and the recognition rate is obviously improved. The result shows that the optimization method based on K means improves the quality and application effect of meteorological digital files.
Meteorological forecasting services and meteorological energy development require data with longer time series, higher spatial and temporal resolution, especially for hourly data. Meteorological data scanned from recording papers have problems such as stains, fading, blurring, and smearing, which cannot meet the requirements of archiving and servicing, and also makes the numerical extraction of images greatly difficult, and the accuracy of extraction results is not guaranteed. This paper proposes an image optimization algorithm based on K means, which can quickly identify and distinguish the image background and data recording curves, filter noise in images, and unify the color and thickness of data recording curves. After optimization, the contrast and sharpness of the images are obviously increased, and the volume is obviously reduced. In practice, it is found that the optimized images save storage resources and cost, and the recognition rate is obviously improved. The result shows that the optimization method based on K means improves the quality and application effect of meteorological digital files.
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.