ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
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2014, 40(4):400-411.
DOI: 10.7519/j.issn.1000-0526.2014.04.002
Abstract:
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
2012, 38(10):1255-1266.
DOI: 10.7519/j.issn.1000-0526.2012.10.012
Abstract:
Precipitation characteristics, environment conditions, generation and development of the mesoscale convective system that brought about the extreme torrential rain in Beijing on 21 July 2012 were analyzed comprehensively in this paper by using various conventional and unconventional data. The results showed that the extreme torrential rain had the characteristics of long duration, great rainfall and wide coverage area and its process consisted of warm area precipitation and frontal precipitation. The warm area rainfall started earlier, the severe precipitation center was scattered and lasted long while the frontal rainfallprocess contained several severe rainfall centers with high precipitation efficiency, lasting a short time.Environment conditions of the mesoscale convective system that triggered this extreme severe rainfall were analyzed. The results showed that interactions of high level divergence, the wind shear and convergence with the vortex in the lower troposphere and the surface wind convergence line provided favorable environment to the severe extreme rain. The warm humid airs from the tropical and sub tropical zones converged over the torrential rain region, continuous and sufficient water vapor manifested as high atmospheric column of precipitable water and strong low level water vapor convergence and other extreme vapor conditions for the torrential rain. In addition, the intense precipitation was triggered by the vortex wind shear, wind disturbance on low level jet, surface wind convergence line and the effect of terrain under the condition of the plentiful water vapour and maintained. With the cold front moved eastward, heavy frontal rainfall was brought by the development and evolution of convective system made by the cold air and the suitable vertical wind shear.Generation and development processes of the mesoscale convective system were also studied. The findings suggested that stratiform cloud precipitation and dispersed convective precipitation occurred firstly in the precipitation process. The warm and steady stratiform cloud precipitation changed to be highly organized convectional precipitation as the cold dry air invaded. Many small scale and mesoscale convective clusters developed into mesoscale convective complex (MCC), leading to the extreme severe precipitation. Since all the directions of the echo long axis, terrain and echo movement were parallel, train effect was obviously seen in the radar echo imegery during this precipitation process. Meanwhile, the radar echo had the characteristics of backward propagation and low centroid which was similar to tropical heavy rainfalls. Finally, a series of scientific problems were proposed according to the integrated analysis on the observation data of this rare torrential rain event, such as the causes for the extreme torrential rain and the extreme rich water vapor, mechanisms for the warm area torrential rain in the north of China, the mechanism for the train effect and backward propagation, mechanisms for the organization and maintenance of the convective cells, the simulation and analysis ability of the numerical models to extreme torrential rains and so on.
Precipitation characteristics, environment conditions, generation and development of the mesoscale convective system that brought about the extreme torrential rain in Beijing on 21 July 2012 were analyzed comprehensively in this paper by using various conventional and unconventional data. The results showed that the extreme torrential rain had the characteristics of long duration, great rainfall and wide coverage area and its process consisted of warm area precipitation and frontal precipitation. The warm area rainfall started earlier, the severe precipitation center was scattered and lasted long while the frontal rainfallprocess contained several severe rainfall centers with high precipitation efficiency, lasting a short time.Environment conditions of the mesoscale convective system that triggered this extreme severe rainfall were analyzed. The results showed that interactions of high level divergence, the wind shear and convergence with the vortex in the lower troposphere and the surface wind convergence line provided favorable environment to the severe extreme rain. The warm humid airs from the tropical and sub tropical zones converged over the torrential rain region, continuous and sufficient water vapor manifested as high atmospheric column of precipitable water and strong low level water vapor convergence and other extreme vapor conditions for the torrential rain. In addition, the intense precipitation was triggered by the vortex wind shear, wind disturbance on low level jet, surface wind convergence line and the effect of terrain under the condition of the plentiful water vapour and maintained. With the cold front moved eastward, heavy frontal rainfall was brought by the development and evolution of convective system made by the cold air and the suitable vertical wind shear.Generation and development processes of the mesoscale convective system were also studied. The findings suggested that stratiform cloud precipitation and dispersed convective precipitation occurred firstly in the precipitation process. The warm and steady stratiform cloud precipitation changed to be highly organized convectional precipitation as the cold dry air invaded. Many small scale and mesoscale convective clusters developed into mesoscale convective complex (MCC), leading to the extreme severe precipitation. Since all the directions of the echo long axis, terrain and echo movement were parallel, train effect was obviously seen in the radar echo imegery during this precipitation process. Meanwhile, the radar echo had the characteristics of backward propagation and low centroid which was similar to tropical heavy rainfalls. Finally, a series of scientific problems were proposed according to the integrated analysis on the observation data of this rare torrential rain event, such as the causes for the extreme torrential rain and the extreme rich water vapor, mechanisms for the warm area torrential rain in the north of China, the mechanism for the train effect and backward propagation, mechanisms for the organization and maintenance of the convective cells, the simulation and analysis ability of the numerical models to extreme torrential rains and so on.
2014, 40(4):389-399.
DOI: 10.7519/j.issn.1000-0526.2014.04.001
Abstract:
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
2014, 40(10):1240-1247.
DOI: 10.7519/j.issn.1000-0526.2014.10.008
Abstract:
The 10 m wind from QuikSCAT and ASCAT orbital data were compared with buoy wind data in the northern South China Sea. The results show that the two satellite data have a good applicability in the northern South China Sea. The QuikSCAT inversion wind speed is 0.46 m·s-1 higher than the buoy wind and ASCAT inversion wind speed is 0.45 m·s-1 higher than buoy wind speed in the offshore sea, though it is 0.07 m·s-1 in the open sea. The absolute error ＜30° of QuikSCAT satellite inversion wind exceeds 50％.The absolute error ＜30° of ASCAT satellite inversion wind passes 56％ in the offshore sea and gets to 64％ in the open sea. When the wind speed is small, satellite inversion wind speed is bigger, when the wind speed is fast, satellite wind speed is slower than the buoy wind. The error in the morning is bigger than that in the evening. But under the condition of 5-10 m·s-1 wind speed, the consistency of the two satellite wind data is better. The offshore wind power resource simulated by WRF model is perhaps overrated. Satellite data may be a beneficial supplement for assessing offshore wind power resource. The satellite inversion wind error analysis also provides a reference for the data assimilation of satellite inversion wind field.
The 10 m wind from QuikSCAT and ASCAT orbital data were compared with buoy wind data in the northern South China Sea. The results show that the two satellite data have a good applicability in the northern South China Sea. The QuikSCAT inversion wind speed is 0.46 m·s-1 higher than the buoy wind and ASCAT inversion wind speed is 0.45 m·s-1 higher than buoy wind speed in the offshore sea, though it is 0.07 m·s-1 in the open sea. The absolute error ＜30° of QuikSCAT satellite inversion wind exceeds 50％.The absolute error ＜30° of ASCAT satellite inversion wind passes 56％ in the offshore sea and gets to 64％ in the open sea. When the wind speed is small, satellite inversion wind speed is bigger, when the wind speed is fast, satellite wind speed is slower than the buoy wind. The error in the morning is bigger than that in the evening. But under the condition of 5-10 m·s-1 wind speed, the consistency of the two satellite wind data is better. The offshore wind power resource simulated by WRF model is perhaps overrated. Satellite data may be a beneficial supplement for assessing offshore wind power resource. The satellite inversion wind error analysis also provides a reference for the data assimilation of satellite inversion wind field.
2014, 40(11):1372-1379.
DOI: 10.7519/j.issn.1000-0526.2014.11.010
Abstract:
The hourly precipitation observation data from 2447 rain gauge records are used to verify and evaluate the satellite precipitation estimation products of Climate Prediction Center Morphing Technique (CMORPH) and Tropical Rainfall Measuring Mission (TRMM) 3B42 during 2007-2010 in China. The results show that the two satellite precipitation data are similar to ground gain gauge data in revealing the spatial patterns of daily mean precipitation amount. The pattern correlation coefficients of 3 h rainfall amount are over 0.5 and 0.4 in most areas, respectively. Bias of two satellite precipitation products are both between the positive and negative 0.25 mm, but there are significant difference between the north and the south. And the mean absolute error, relative error and root mean square error all have a significant seasonal periodic variations. The two satellite precipitation products can reflect the summer rainfall diurnal variation well in most parts of China, but there are also clear distinctions in some areas. The overall vacancy retrieval rate of CMORPH and TRMM 3B42 products are 7.23% and 2.63%, overall missing retrieval rate are 3.25% and 5.5%, respectively.
The hourly precipitation observation data from 2447 rain gauge records are used to verify and evaluate the satellite precipitation estimation products of Climate Prediction Center Morphing Technique (CMORPH) and Tropical Rainfall Measuring Mission (TRMM) 3B42 during 2007-2010 in China. The results show that the two satellite precipitation data are similar to ground gain gauge data in revealing the spatial patterns of daily mean precipitation amount. The pattern correlation coefficients of 3 h rainfall amount are over 0.5 and 0.4 in most areas, respectively. Bias of two satellite precipitation products are both between the positive and negative 0.25 mm, but there are significant difference between the north and the south. And the mean absolute error, relative error and root mean square error all have a significant seasonal periodic variations. The two satellite precipitation products can reflect the summer rainfall diurnal variation well in most parts of China, but there are also clear distinctions in some areas. The overall vacancy retrieval rate of CMORPH and TRMM 3B42 products are 7.23% and 2.63%, overall missing retrieval rate are 3.25% and 5.5%, respectively.
2012, 38(11):1313-1329.
DOI: 10.7519/j.issn.1000-0526.2012.11.001
Abstract:
On 21 July 2012 Beijing experienced the most severe rainfall event since August 1963. The extreme rainfall induced flooding killed over 100 people and the property damage is over 11.64 billion RMB yuan (about 2 billion U.S. dollars). Based on the routine upper level and surface observation, the satellite and radar data, a detailed analysis and investigation have been done on this event. The major results are as following: (1) The upper level trough accompanied by surface cold front moving toward east blocked by the subtropical high provides favorable synoptic scale conditions for torrential rain event in Beijing area. (2) The presence of a tropical cyclone over the South China Sea near the coastline led to the establishment and enhancement of southeastward and southward low level jet toward Beijing area, providing plenty of water vapor to Beijing area. (3) The development of Hetao vertex on 20 July led to the formation of a meso α scale MCS over that area, and its high value of vertical helicity made it well organized and longlived. This MCS moved with the upper level trough eastward, and was over Huabei region （including Beijing area） on the second day (21 July), producing extreme rainfall over Beijing area. (4) The south east low level jet constantly triggered new convective cells on the east slope of the Taihang Mountain Range, then moved to northeast direction into Beijing area, leading to the torrential rainfall and severe flooding there.
On 21 July 2012 Beijing experienced the most severe rainfall event since August 1963. The extreme rainfall induced flooding killed over 100 people and the property damage is over 11.64 billion RMB yuan (about 2 billion U.S. dollars). Based on the routine upper level and surface observation, the satellite and radar data, a detailed analysis and investigation have been done on this event. The major results are as following: (1) The upper level trough accompanied by surface cold front moving toward east blocked by the subtropical high provides favorable synoptic scale conditions for torrential rain event in Beijing area. (2) The presence of a tropical cyclone over the South China Sea near the coastline led to the establishment and enhancement of southeastward and southward low level jet toward Beijing area, providing plenty of water vapor to Beijing area. (3) The development of Hetao vertex on 20 July led to the formation of a meso α scale MCS over that area, and its high value of vertical helicity made it well organized and longlived. This MCS moved with the upper level trough eastward, and was over Huabei region （including Beijing area） on the second day (21 July), producing extreme rainfall over Beijing area. (4) The south east low level jet constantly triggered new convective cells on the east slope of the Taihang Mountain Range, then moved to northeast direction into Beijing area, leading to the torrential rainfall and severe flooding there.
2010, 36(10):102-105.
DOI: 10.7519/j.issn.1000-0526.2010.10.017
Abstract:
By using the meteorological monitoring data, the meteorological causes for the massive mudslide in Zhouqu which occurred on 8 August 2010 are analyzed. Results demonstrate that the severe convective weather process with heavy precipitation is the main cause for this massive mudslide. The characteristics of this heavy precipitation are local, large intensity in short time and paroxysmal. The data of radar and satellites suggest that the weather system has obviously mesoscale characteristics. This kind of mesoscale weather system is produced by the forcing of the shear line in the low level, when the cold air in the high level is moving eastward and southward.
By using the meteorological monitoring data, the meteorological causes for the massive mudslide in Zhouqu which occurred on 8 August 2010 are analyzed. Results demonstrate that the severe convective weather process with heavy precipitation is the main cause for this massive mudslide. The characteristics of this heavy precipitation are local, large intensity in short time and paroxysmal. The data of radar and satellites suggest that the weather system has obviously mesoscale characteristics. This kind of mesoscale weather system is produced by the forcing of the shear line in the low level, when the cold air in the high level is moving eastward and southward.
8 Characteristics and Synoptic Mechanism of the July 2016 Extreme Precipitation Event in North China
FU Jiaolan
,
MA Xuekuan
,
CHEN Tao
,
ZHANG Fang
,
ZHANG Xidi
,
SUN Jun
,
QUAN Wanqing
,
YANG Shunan
,
SHEN Xiaolin
2017, 43(5):528-539.
DOI: 10.7519/j.issn.1000-0526.2017.05.002
Abstract:
An extremely severe precipitation event took place in North China in 19-20 July 2016. It was characterized by large rainfall, persistent rainfall, warm cloud rainfall, strong local rainfall intensity and orographic precipitation. Its rainfall was larger than that of the extreme rainfall in 3-5 August 1996, and only next to the amount of the 2-7 August 1963 extreme rainfall event. It occurred under the circulation background of the South Asia high moving eastward, the West Pacific subtropical high moving northwestward and the low vortex in the westerlies developing in midhigh latitude. The abnormal development of Huanghuai cyclone, southwest and southeast lowlevel jets, and the abnormally abundant moisture indicates that the dynamic lifting and moisture conditions favored this severe rainfall process significantly. The whole rainfall event presented clearly the phase characteristics, and could be divided into two stages. The first stage was the orographic rainfall caused by the easterly winds ahead of the trough from the early morning to the daytime of 19 July, while the second part was produced by spiral rain bands in the north side of Huanghuai cyclone from the night of 19 to the daytime of 20 July. In the first stage, the easterly lowlevel jet was lifted by the Taihang Mountains, which continuously triggered the convective cells along the east edge of the mountains. The weak dry and cold advection at midlevel and the strong warm and wet advection at lowlevel jointly maintained the convective instability. The cold pool generated by heavy rainfall and the mesoscale frontogenesis process created by local orographic effect provided favorable conditions for severe convections to occur continuously. The second stage rainfall was mainly related to the development of cutoff vortex and Huanghuai cyclone. The blocking of the high pressure system slowed the steps of Huanghuai cyclone in North China, thus leading to the longlasting rainfall process.
An extremely severe precipitation event took place in North China in 19-20 July 2016. It was characterized by large rainfall, persistent rainfall, warm cloud rainfall, strong local rainfall intensity and orographic precipitation. Its rainfall was larger than that of the extreme rainfall in 3-5 August 1996, and only next to the amount of the 2-7 August 1963 extreme rainfall event. It occurred under the circulation background of the South Asia high moving eastward, the West Pacific subtropical high moving northwestward and the low vortex in the westerlies developing in midhigh latitude. The abnormal development of Huanghuai cyclone, southwest and southeast lowlevel jets, and the abnormally abundant moisture indicates that the dynamic lifting and moisture conditions favored this severe rainfall process significantly. The whole rainfall event presented clearly the phase characteristics, and could be divided into two stages. The first stage was the orographic rainfall caused by the easterly winds ahead of the trough from the early morning to the daytime of 19 July, while the second part was produced by spiral rain bands in the north side of Huanghuai cyclone from the night of 19 to the daytime of 20 July. In the first stage, the easterly lowlevel jet was lifted by the Taihang Mountains, which continuously triggered the convective cells along the east edge of the mountains. The weak dry and cold advection at midlevel and the strong warm and wet advection at lowlevel jointly maintained the convective instability. The cold pool generated by heavy rainfall and the mesoscale frontogenesis process created by local orographic effect provided favorable conditions for severe convections to occur continuously. The second stage rainfall was mainly related to the development of cutoff vortex and Huanghuai cyclone. The blocking of the high pressure system slowed the steps of Huanghuai cyclone in North China, thus leading to the longlasting rainfall process.
XIONG Yajun
,
LIAO Xiaonong
,
LI Ziming
,
ZHANG Xiaoling
,
SUN Zhaobin
,
ZHAO Xiujuan
,
ZHAO Pusheng
,
MA Xiaohui
,
PU Weiwei
2015, 41(1):98-104.
DOI: 10.7519/j.issn.1000-0526.2015.01.012
Abstract:
Based on meteorological data and PM2.5 concentration data of 2013， the statistical analysis shows that temperature, pressure, relative humidity, dew point temperature, surface wind, U wind， V wind and PM2.5 hourly concentration are the 7 key factors affecting the haze grade of Beijing Area. The attribute vectors of KNN training sample set are the above 7 factors and the label vector is haze grade. The classifier can be established combining KNN Data Mining Algorithm and its best value is parameter K=3. The classification accuracy of the 13 meteorological stations is 88.2%. The forecasting model based on KNN Algorithm has good accuracy. When it predicts no haze, the accuracy rate is 91.8% and missing forecast chance is very small. When mild, moderate or severe haze is predicted, the probability of empty forecast is only 4.7%, 1.4% and 2.6%, respectively. There was one frog haze weather process from 29 August to 2 September 2014 in Beijing Area. Its prediction results show the forecast accuracy of Nanjiao, Miyun and Yanqing is 74%, 64% and 84% respectively, but the accuracy of the haze grade remains to be further improved.
Based on meteorological data and PM2.5 concentration data of 2013， the statistical analysis shows that temperature, pressure, relative humidity, dew point temperature, surface wind, U wind， V wind and PM2.5 hourly concentration are the 7 key factors affecting the haze grade of Beijing Area. The attribute vectors of KNN training sample set are the above 7 factors and the label vector is haze grade. The classifier can be established combining KNN Data Mining Algorithm and its best value is parameter K=3. The classification accuracy of the 13 meteorological stations is 88.2%. The forecasting model based on KNN Algorithm has good accuracy. When it predicts no haze, the accuracy rate is 91.8% and missing forecast chance is very small. When mild, moderate or severe haze is predicted, the probability of empty forecast is only 4.7%, 1.4% and 2.6%, respectively. There was one frog haze weather process from 29 August to 2 September 2014 in Beijing Area. Its prediction results show the forecast accuracy of Nanjiao, Miyun and Yanqing is 74%, 64% and 84% respectively, but the accuracy of the haze grade remains to be further improved.
MA Zhongyuan
,
ZHU Chunqiao
,
WANG Huajun
,
YU Bing
,
PAN Jiangping
,
LIN Chun
,
XIAO Yuling
,
GUI Baoyu
2010, 36(4):132-136.
DOI: 10.7519/j.issn.1000-0526.2010.4.024
Abstract:
With the development of the meteorological cause and the requirement of fine weather forecast, the requirement and concept of time are been recognized more and more important for meteorological operational system. The unified time of meteorological operational system plays an important role in improving the quality of observation data. GPSNET time service system uses the GPS time source and system received software technology to make time service for computer. Standard time can be transmitted to certain users by net with Network time service publishing and Network user terminal received software. At the same time, the security of the GPS system and Network is considered fully. The results show that: GPSNET time service system can obtain GPS time source information accurately and release to user terminals through network technology to make meteorological oper〖HJ〗ational system obtain the standard time (error <1 s). The way of network publishing and meteorological internal network limitation can reduce the server and user terminal’s burden effectively and preventing external net virus’s invasion. The quick, exact and synchronization solution of time service is provided for meteorological equipment and meteorological operation by GPSNet time service system.
With the development of the meteorological cause and the requirement of fine weather forecast, the requirement and concept of time are been recognized more and more important for meteorological operational system. The unified time of meteorological operational system plays an important role in improving the quality of observation data. GPSNET time service system uses the GPS time source and system received software technology to make time service for computer. Standard time can be transmitted to certain users by net with Network time service publishing and Network user terminal received software. At the same time, the security of the GPS system and Network is considered fully. The results show that: GPSNET time service system can obtain GPS time source information accurately and release to user terminals through network technology to make meteorological oper〖HJ〗ational system obtain the standard time (error <1 s). The way of network publishing and meteorological internal network limitation can reduce the server and user terminal’s burden effectively and preventing external net virus’s invasion. The quick, exact and synchronization solution of time service is provided for meteorological equipment and meteorological operation by GPSNet time service system.
2018, 44(7):892-901.
DOI: 10.7519/j.issn.10000526.2018.07.004
Abstract:
Based on meteorological data from 70 automatic weather stations and 365 traffic meteorological observation stations of Jiangsu Province, a heavy fog process that occurred in Jiangsu in 11-12 February 2016 is investigated. The results show this fog process features that the fog formed and intensified explosively. At most stations, the dense fog formed rapidly with the visibility dropping directly from 1000 m above, and there was multiple burst enhancement phenomena in some areas. Along with the opened sky at night, the longwave radiation cooling also strengthened, which was an important cause for the formation and explosive development of the wide range of heavy fog. Meanwhile, the prophase rainfall provided basic conditions for the formation of the heavy fog, and also was the direct cause of the enhanced evaporation and explosive increase of heavy fog at some sites after sunrise. In addition, strong inversion temperature provided stable atmospheric conditions for the explosive development of fog. The lowlevel jet near the top of inversion temperature promoted the maintenance and enhancing of the strong inversion, which played an important role in the explosive development of heavy fog.
Based on meteorological data from 70 automatic weather stations and 365 traffic meteorological observation stations of Jiangsu Province, a heavy fog process that occurred in Jiangsu in 11-12 February 2016 is investigated. The results show this fog process features that the fog formed and intensified explosively. At most stations, the dense fog formed rapidly with the visibility dropping directly from 1000 m above, and there was multiple burst enhancement phenomena in some areas. Along with the opened sky at night, the longwave radiation cooling also strengthened, which was an important cause for the formation and explosive development of the wide range of heavy fog. Meanwhile, the prophase rainfall provided basic conditions for the formation of the heavy fog, and also was the direct cause of the enhanced evaporation and explosive increase of heavy fog at some sites after sunrise. In addition, strong inversion temperature provided stable atmospheric conditions for the explosive development of fog. The lowlevel jet near the top of inversion temperature promoted the maintenance and enhancing of the strong inversion, which played an important role in the explosive development of heavy fog.
2013, 39(7):874-882.
DOI: 10.7519/j.issn.1000-0526.2013.07.008
Abstract:
Based on conventional observational data and radar data, the elevated thunderstorm hail process in Guangxi in early spring of 2012 is analyzed. The results show that: (1) Hail accompanied by thunderstorm occurs on the surface about 1000 km away from the front, and boundary layer is controlled by cold high pressure. The smaller winds at 850 hPa, strong jet stream at 700 hPa and above layer, strong vertical wind shear between 700 hPa and 850 hPa and eastward move of cold trough at 500 hPa provide the trigger condition for the occurrence of the convection. (2) Hail occurs in the range of approximately 200 km away from the shear line at 850 hPa, where there is strong intensity of the pressure surface frontal zone. The negative variable temperature in front of the upper trough increases the temperature difference in vertical direction between 700 hPa and 500 hPa, resulting in the increase of stratification convective instability. When the trough at 500 hPa moves up to the air above the frontal zone, the frontal slope becomes steep, and the upward movement strengthens while the instability increases. All of these make the ice embryo grow in the troposphere and form hail. (3) The storm tracking information displays that storms are generated in high altitudes, and the centroids are 5-6 km high. After the storm is generated, the centroids gradually develop to lower layer with time going. The maximum reflectivity and liquid water content are not large, showing the significant characteristics of the elevated thunderstorms.
Based on conventional observational data and radar data, the elevated thunderstorm hail process in Guangxi in early spring of 2012 is analyzed. The results show that: (1) Hail accompanied by thunderstorm occurs on the surface about 1000 km away from the front, and boundary layer is controlled by cold high pressure. The smaller winds at 850 hPa, strong jet stream at 700 hPa and above layer, strong vertical wind shear between 700 hPa and 850 hPa and eastward move of cold trough at 500 hPa provide the trigger condition for the occurrence of the convection. (2) Hail occurs in the range of approximately 200 km away from the shear line at 850 hPa, where there is strong intensity of the pressure surface frontal zone. The negative variable temperature in front of the upper trough increases the temperature difference in vertical direction between 700 hPa and 500 hPa, resulting in the increase of stratification convective instability. When the trough at 500 hPa moves up to the air above the frontal zone, the frontal slope becomes steep, and the upward movement strengthens while the instability increases. All of these make the ice embryo grow in the troposphere and form hail. (3) The storm tracking information displays that storms are generated in high altitudes, and the centroids are 5-6 km high. After the storm is generated, the centroids gradually develop to lower layer with time going. The maximum reflectivity and liquid water content are not large, showing the significant characteristics of the elevated thunderstorms.
2012, 38(2):164-173.
DOI: 10.7519/j.issn.1000-0526.2012.02.004
Abstract:
Many weather forecasters seem to have acquaintance with most of basic concepts or fundamental theories which are connected with severe convection, but some of them are misapplied frequently by some forecasters when they are engaged in severe convective weather analysis or forecasting argumentation. Due to the above problem, some basic concepts and fundamental theories should be explained from the view of forecasting application. The following issues are discussed in this paper. They are the relationship between humidity and water vapor content, the role of clod air during the precipitation process, the fundamental theories connected with thermal and dynamic instability, the sounding analysis related to instability parameters, the relationship between helicity or moist potential vorticity and instability, the relationship among the convergence line, lifting velocity and convective vertical movement, and the essential connection between the synoptic patterns and severe convective phenomena.
Many weather forecasters seem to have acquaintance with most of basic concepts or fundamental theories which are connected with severe convection, but some of them are misapplied frequently by some forecasters when they are engaged in severe convective weather analysis or forecasting argumentation. Due to the above problem, some basic concepts and fundamental theories should be explained from the view of forecasting application. The following issues are discussed in this paper. They are the relationship between humidity and water vapor content, the role of clod air during the precipitation process, the fundamental theories connected with thermal and dynamic instability, the sounding analysis related to instability parameters, the relationship between helicity or moist potential vorticity and instability, the relationship among the convergence line, lifting velocity and convective vertical movement, and the essential connection between the synoptic patterns and severe convective phenomena.
2010, 36(3):9-18.
DOI: 10.7519/j.issn.1000-0526.2010.3.002
Abstract:
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
2017, 43(7):769-780.
DOI: 10.7519/j.issn.1000-0526.2017.07.001
Abstract:
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
2015, 41(2):212-218.
DOI: 10.7519/j.issn.1000-0526.2015.02.009
Abstract:
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
2017, 43(4):508-512.
DOI: 10.7519/j.issn.1000-0526.2017.04.014
Abstract:
The main characteristics of the general atmospheric circulation in January 2017 are as follows. There was one polar vortex center in the Northern Hemisphere with the stronger strength than normal year. The circulation presented the troughridgetrough pattern in middlehigh latitudes. The south branch was as strong as normal, located near the west of 90°E averagely. The subtropical high also had the same strength as usual. In addition, the monthly mean precipitation is 12.4 mm, 6% less than normal and mean temperature is -3.4℃, 1.6℃ higher than normal (-5.0℃), which is the third high value for the corresponding period since 1961. There were two cold air processes, two major rainfall processes and two largescale foghaze weather processes during this month. Among them the foghaze event from 30 December 2016 to 6 January 2017 was characterized by the most extensive, the longest and the most intensive foghaze weather in January.
The main characteristics of the general atmospheric circulation in January 2017 are as follows. There was one polar vortex center in the Northern Hemisphere with the stronger strength than normal year. The circulation presented the troughridgetrough pattern in middlehigh latitudes. The south branch was as strong as normal, located near the west of 90°E averagely. The subtropical high also had the same strength as usual. In addition, the monthly mean precipitation is 12.4 mm, 6% less than normal and mean temperature is -3.4℃, 1.6℃ higher than normal (-5.0℃), which is the third high value for the corresponding period since 1961. There were two cold air processes, two major rainfall processes and two largescale foghaze weather processes during this month. Among them the foghaze event from 30 December 2016 to 6 January 2017 was characterized by the most extensive, the longest and the most intensive foghaze weather in January.
2015, 41(1):34-44.
DOI: 10.7519/j.issn.1000-0526.2015.01.004
Abstract:
Two cold air events that happened in Qiongzhou Channel were modeled by mesoscale dynamic model WRF and diagnostic model CALMET, and the research focuses on the near surface wind. Horizontal grid spaces of four nests in WRF model are 27 km, 9 km, 3 km and 1 km respectively. The fourth nest with 1 km grid space of CALMET and the fifth nest in WRF is set as model initial field for down grid space to 200 m, so as to get the final field which is able to fulfill the resolution required. Wind speed and direction of CALMET 200 m, WRF 1 km and WRF 200 m are contrasted with the observed winds at 21 observing stations (including 6 anemometer towers) distributed in the two sides of the Qiongzhou Channel. The main conclusions are as follows: (1) CALMET 200 m speed RMSE is much less than the two other experiments with time going, but there is not any notable difference in wind direction RMSE. In the height of 60-80 m, RMSE can not show any difference in wind direction, either. (2) At 10 m height, CALMET 200 m wind is diagnosed to be the best with the average error varing from 4 m·s-1 to 0 m·s-1. The average errors of the other two experiments are about 2 m·s-1 bigger than CALMET 200 m. The distribution of errors is more concentrated in direction. In 60-80 m height, the three experiments have almost the same results. But the result of WRF 200 m wind speed shows worse than the results of the other two experiments, while not differences in wind direction are found in the three experiments. (3) Smaller wind speed and direction average errors of WRF/CALMET system in non cold air condition show that the system can perform better when the atmospheric stratification is relatively stable.
Two cold air events that happened in Qiongzhou Channel were modeled by mesoscale dynamic model WRF and diagnostic model CALMET, and the research focuses on the near surface wind. Horizontal grid spaces of four nests in WRF model are 27 km, 9 km, 3 km and 1 km respectively. The fourth nest with 1 km grid space of CALMET and the fifth nest in WRF is set as model initial field for down grid space to 200 m, so as to get the final field which is able to fulfill the resolution required. Wind speed and direction of CALMET 200 m, WRF 1 km and WRF 200 m are contrasted with the observed winds at 21 observing stations (including 6 anemometer towers) distributed in the two sides of the Qiongzhou Channel. The main conclusions are as follows: (1) CALMET 200 m speed RMSE is much less than the two other experiments with time going, but there is not any notable difference in wind direction RMSE. In the height of 60-80 m, RMSE can not show any difference in wind direction, either. (2) At 10 m height, CALMET 200 m wind is diagnosed to be the best with the average error varing from 4 m·s-1 to 0 m·s-1. The average errors of the other two experiments are about 2 m·s-1 bigger than CALMET 200 m. The distribution of errors is more concentrated in direction. In 60-80 m height, the three experiments have almost the same results. But the result of WRF 200 m wind speed shows worse than the results of the other two experiments, while not differences in wind direction are found in the three experiments. (3) Smaller wind speed and direction average errors of WRF/CALMET system in non cold air condition show that the system can perform better when the atmospheric stratification is relatively stable.
2017, 43(12):1527-1533.
DOI: 10.7519/j.issn.1000-0526.2017.12.008
Abstract:
To explicitly investigate the influence of precipitation on visibility and PM2.5 concentration, minutescale observations of Hangzhou during 2014-2015 are used to comparatively analyze the distribution characteristics of visibility and PM2.5 concentration under different levels of precipitation, and, furthermore, the quantitative impacts of precipitation with different intensities on visibility and PM2.5 concentration are studied. The results indicate that the intensity and duration of precipitation can significantly modulate visibility and PM2.5 concentration. Consistent and stable rainfall are easy to trigger long lowvisibility scenario, and the sudden heavy precipitation is an important factor inducing the sharpdecrease of visibility. With the rise of rainfall, the visibility changes from rapiddecline to slowdecline and there exists an inflection point. The removing effect of precipitation on PM2.5 concentration can be mediated by the intensity of rainfall and the PM2.5 concentration before raining. When there is modest/small rainfall, the removing effect usually occurs several time later. However, heavy precipitation is able to remove PM2.5 quickly. Basically, synchronous changes among precipitation, PM2.5 concentration and visibility can appear. Based on the two factors of precipitation intensity and PM2.5 concentration before raining, a quantitative statistical model reflecting the influence of rainfall on PM2.5 concentration is constructed with the nonlinear fitting technology, and the modeling results agree well with observations. Finally, the existing limitations and some scientific issues which need further exploring in the future are discussed.
To explicitly investigate the influence of precipitation on visibility and PM2.5 concentration, minutescale observations of Hangzhou during 2014-2015 are used to comparatively analyze the distribution characteristics of visibility and PM2.5 concentration under different levels of precipitation, and, furthermore, the quantitative impacts of precipitation with different intensities on visibility and PM2.5 concentration are studied. The results indicate that the intensity and duration of precipitation can significantly modulate visibility and PM2.5 concentration. Consistent and stable rainfall are easy to trigger long lowvisibility scenario, and the sudden heavy precipitation is an important factor inducing the sharpdecrease of visibility. With the rise of rainfall, the visibility changes from rapiddecline to slowdecline and there exists an inflection point. The removing effect of precipitation on PM2.5 concentration can be mediated by the intensity of rainfall and the PM2.5 concentration before raining. When there is modest/small rainfall, the removing effect usually occurs several time later. However, heavy precipitation is able to remove PM2.5 quickly. Basically, synchronous changes among precipitation, PM2.5 concentration and visibility can appear. Based on the two factors of precipitation intensity and PM2.5 concentration before raining, a quantitative statistical model reflecting the influence of rainfall on PM2.5 concentration is constructed with the nonlinear fitting technology, and the modeling results agree well with observations. Finally, the existing limitations and some scientific issues which need further exploring in the future are discussed.
ZHANG Xiaoling
,
ZHANG Tao
,
LIU Xinhua
,
ZHOU Qingliang
,
CHEN Yun
,
ZHOU Xiaoxia
,
ZHENG Yongguang
,
ZHAO Surong
2010, 36(7):143-150.
DOI: 10.7519/j.issn.1000-0526.2010.7.021
Abstract:
Mesoscale severe weather forecasting ability is limited, in some sense for a lack of valid analysis on mesoscale convective systems and its favorable environments. This paper introduces the mesoscale weather chart analysis techniq ue which was tested in the National Meteorological Center (NMC). Mesoscale weath er chart analyzes the favorable environmental conditions of mesoscale convective systems based on observational data and numerical weather forecast outputs. It includes upperair composite chart and surface chart. In the upperair composite ch art, by analyzing wind, temperature, moisture, temperature change and height change, the diagnostic systems and features in all the lower, middle and upper t roposphere isobaric layers are combined into one plot, which can clearly displa y the available environments and synoptic pattern of severe convective weather. In the surface chart, the analysis contents are pressure, wind, temperature, moi sture, convective weather phenomena and all kinds of boundaries (fronts). The te st in NMC shows that mesoscale weather chart analysis is a dependable means for severe convective weather outlook forecasting.
Mesoscale severe weather forecasting ability is limited, in some sense for a lack of valid analysis on mesoscale convective systems and its favorable environments. This paper introduces the mesoscale weather chart analysis techniq ue which was tested in the National Meteorological Center (NMC). Mesoscale weath er chart analyzes the favorable environmental conditions of mesoscale convective systems based on observational data and numerical weather forecast outputs. It includes upperair composite chart and surface chart. In the upperair composite ch art, by analyzing wind, temperature, moisture, temperature change and height change, the diagnostic systems and features in all the lower, middle and upper t roposphere isobaric layers are combined into one plot, which can clearly displa y the available environments and synoptic pattern of severe convective weather. In the surface chart, the analysis contents are pressure, wind, temperature, moi sture, convective weather phenomena and all kinds of boundaries (fronts). The te st in NMC shows that mesoscale weather chart analysis is a dependable means for severe convective weather outlook forecasting.
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