ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 38,Issue 2,2012 Table of Contents
2012, 38(2):129-146.
DOI: 10.7519/j.issn.1000-0526.2012.02.001
Abstract:
Meteorological satellites and satellite meteorology have been developed into a new era today, this paper overviews the role and impact of meteorological satellites in atmospheric sciences in different stages, as well as the challenges in science and technology to weather satellite programs. The science challenges include improving radiometric calibration and validation, developing fast and accurate radiative transfer models, assimilating atmospheric water vapor and cloud information from satellite measurements in numerical weather prediction (NWP) models and developing the advanced retrieval methodologies.
Meteorological satellites and satellite meteorology have been developed into a new era today, this paper overviews the role and impact of meteorological satellites in atmospheric sciences in different stages, as well as the challenges in science and technology to weather satellite programs. The science challenges include improving radiometric calibration and validation, developing fast and accurate radiative transfer models, assimilating atmospheric water vapor and cloud information from satellite measurements in numerical weather prediction (NWP) models and developing the advanced retrieval methodologies.
2012, 38(2):147-154.
DOI: 10.7519/j.issn.1000-0526.2012.02.002
Abstract:
A review of hydrometeorological research is presented from aspects of quantitative precipitation estimation (QPE) and forescasting (QPF), hydrological model, hydrometeorological forecasting and flood forecasting. The investigation shows that the raingaugeradarsatellite quantitative precipitation analysis method is the main way for the high resolution precipitation distribution of quantitative precipitation estimation, and the ensemble prediction precipitation system based on NWP multimodel is a chief way for the high accuracy of quantitative precipitation forecast. Meanwhile, the distributed hydrological model is the development direction of hydrological model. The incorporation of quantitative precipitation forecasts into a hydrometeorological and flood forecasting system can increase flood forecast lead times. Hydrological ensemble forecasting system is the most popular prediction technique in the world and the bidirectional feedback model combining NWP model and hydrological model is another future development direction.
A review of hydrometeorological research is presented from aspects of quantitative precipitation estimation (QPE) and forescasting (QPF), hydrological model, hydrometeorological forecasting and flood forecasting. The investigation shows that the raingaugeradarsatellite quantitative precipitation analysis method is the main way for the high resolution precipitation distribution of quantitative precipitation estimation, and the ensemble prediction precipitation system based on NWP multimodel is a chief way for the high accuracy of quantitative precipitation forecast. Meanwhile, the distributed hydrological model is the development direction of hydrological model. The incorporation of quantitative precipitation forecasts into a hydrometeorological and flood forecasting system can increase flood forecast lead times. Hydrological ensemble forecasting system is the most popular prediction technique in the world and the bidirectional feedback model combining NWP model and hydrological model is another future development direction.
2012, 38(2):155-163.
DOI: 10.7519/j.issn.1000-0526.2012.02.003
Abstract:
Southwest vortex is one of the main rainfall weather systems in China. The research on southwest vortex can be traced back to about forty years in the twentieth century. First, the review of southwest vortex research on its activities, structures, mechanisms of forming, maintaining and eastwards moving has been presented in the last half century. Then, in order to deepen the research on the southwest vortex and to heighten the understanding of weather systems such as southwest vortex, there are some deficiencies to be pointed out, such as the understanding of southwest vortex cloud system and radar echo characteristics, the effects of systems at different scales on southwest vortex forming and developing, the impact of atmospheric boundary layer on the vortex forming and developing, the study on abnormity mechanics of southwest vortex activities and so on.
Southwest vortex is one of the main rainfall weather systems in China. The research on southwest vortex can be traced back to about forty years in the twentieth century. First, the review of southwest vortex research on its activities, structures, mechanisms of forming, maintaining and eastwards moving has been presented in the last half century. Then, in order to deepen the research on the southwest vortex and to heighten the understanding of weather systems such as southwest vortex, there are some deficiencies to be pointed out, such as the understanding of southwest vortex cloud system and radar echo characteristics, the effects of systems at different scales on southwest vortex forming and developing, the impact of atmospheric boundary layer on the vortex forming and developing, the study on abnormity mechanics of southwest vortex activities and so on.
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.
2012, 38(2):174-181.
DOI: 10.7519/j.issn.1000-0526.2012.02.005
Abstract:
The west and north parts of Beijing area are mountainous and the urban heat island effect is obvious in Beijing area, these may influence the distribution and intensity of the rainfall. Using the intensified observation and analysis data including wind profile data, temperature elements of surface automatic weather stations (AWS), the wind distribution and vertical divergence of Variational Doppler Radar Analysis System (VDRAS ), the effects of topography and urban heat island on a mesoβ torrential rain in Beijing area are studied in the afternoon on July 9, 2010. Result shows: (1) When the wind is toward the mountain, the rainfall gets stronger at the windward slope; (2) The urban heat effect is obvious before the rainfall begins, the convergence at low levels because of the effect is about 1000 m high, and at the same time the temperature gradient caused by the urban heat effect can cause vertical wind shear, so that both the convergence of low level and the vertical wind shear can lead to the grow and development of the convective system; (3) Once strong convective precipitation begins on the windward slope, the positive feedback between rainfall intensity and southeast wind velocity appears, and the process is an essential condition to form mesoβ scale torrential rain.
The west and north parts of Beijing area are mountainous and the urban heat island effect is obvious in Beijing area, these may influence the distribution and intensity of the rainfall. Using the intensified observation and analysis data including wind profile data, temperature elements of surface automatic weather stations (AWS), the wind distribution and vertical divergence of Variational Doppler Radar Analysis System (VDRAS ), the effects of topography and urban heat island on a mesoβ torrential rain in Beijing area are studied in the afternoon on July 9, 2010. Result shows: (1) When the wind is toward the mountain, the rainfall gets stronger at the windward slope; (2) The urban heat effect is obvious before the rainfall begins, the convergence at low levels because of the effect is about 1000 m high, and at the same time the temperature gradient caused by the urban heat effect can cause vertical wind shear, so that both the convergence of low level and the vertical wind shear can lead to the grow and development of the convective system; (3) Once strong convective precipitation begins on the windward slope, the positive feedback between rainfall intensity and southeast wind velocity appears, and the process is an essential condition to form mesoβ scale torrential rain.
2012, 38(2):182-187.
DOI: 10.7519/j.issn.1000-0526.2012.02.006
Abstract:
Using upper and lower weather chart data, sounding data, radar and satellite data, the cold airflow snowfall events which happened in recent 10 years in Shanghai area were studied and the mechanism for this kind of weather was preliminarily revealed. The conclusions are as follows: there are total 12 cold airflow snowfall events over the year 2000 to 2009 in Shanghai area, which take up a proportion of 25% of the whole snowfall weather days for recent 10 years in Shanghai area. Most of the events, when the snowfall is notable, happened to have a trough behind Shanghai area on the 500 hPa weather chart. Before the cold airflow snowfall, the stratification in the low layer of the sounding data at Baoshan Station was often unstable, and it was usually very moist between 850 and 925 hPa levels. On the satellite image of cold airflow snowfall, the cloud which has a shape of white bright wavy structure and a height below 3000 m, goes in the same way as the trend of coastline. Radar reflectivity was very weak, usually less than 35 dBz for most of the cold airflow snowfall events, and the difference in temperature between sea surface and 850 hPa level was 10 to 14℃, while on the 925 hPa level the difference was 8 to 11℃. The wind direction of Baoshan Station was NWWNWN and wind speed was 3—6 m·s-1 during cold airflow snowfall. Compared with Shandong Peninsula, the cold airflow snowfall in Shanghai area has a smaller range, shorter duration and lower intensity because of its special geographical position and topographic condition.
Using upper and lower weather chart data, sounding data, radar and satellite data, the cold airflow snowfall events which happened in recent 10 years in Shanghai area were studied and the mechanism for this kind of weather was preliminarily revealed. The conclusions are as follows: there are total 12 cold airflow snowfall events over the year 2000 to 2009 in Shanghai area, which take up a proportion of 25% of the whole snowfall weather days for recent 10 years in Shanghai area. Most of the events, when the snowfall is notable, happened to have a trough behind Shanghai area on the 500 hPa weather chart. Before the cold airflow snowfall, the stratification in the low layer of the sounding data at Baoshan Station was often unstable, and it was usually very moist between 850 and 925 hPa levels. On the satellite image of cold airflow snowfall, the cloud which has a shape of white bright wavy structure and a height below 3000 m, goes in the same way as the trend of coastline. Radar reflectivity was very weak, usually less than 35 dBz for most of the cold airflow snowfall events, and the difference in temperature between sea surface and 850 hPa level was 10 to 14℃, while on the 925 hPa level the difference was 8 to 11℃. The wind direction of Baoshan Station was NWWNWN and wind speed was 3—6 m·s-1 during cold airflow snowfall. Compared with Shandong Peninsula, the cold airflow snowfall in Shanghai area has a smaller range, shorter duration and lower intensity because of its special geographical position and topographic condition.
2012, 38(2):189-196.
DOI: 10.7519/j.issn.1000-0526.2012.02.007
Abstract:
Based on the daily hail data at 175 stations in Beijing, Tianjin and Hebei Province (BTH for short hereinafter) during 1979 to 2008, using climate trend coefficient, trend rate, concentration degree (CD), concentration period (CP), and continuous power spectrum, the multiple timescale variation characteristics and trend variation of hail in BTH area are analyzed. It focuses on the four different key regions. Meanwhile, the significance of trend coefficient is tested by Monte Carlo scheme. The results show that the hail during last 30 years has increased obviously, the negative trend of hail is that reduction is larger in the northern areas than the southern areas, and larger in the mountain regions than the plain regions; there are 2.0-2.5 year periodic oscillations for interannual variations in all key regions, the interannual change of the occurring frequency of hail is characteristic of quasibiennial oscillation (QBO); The hailconcentration degree (HCD) in the southern area was the biggest, indicating that the time when hail occurred in this key region was relatively concentrated; The hailconcentration period (HCP) in all regions except southern area being in pentad 31 (about early June), was pentads 36-37， indicating that hail mainly occurred from late June to early July. Analysis on abrupt climate change using accumulated anomaly method and Yamamoto method shows that an abrupt decreasing occurred in 1993, especially in mountain regions.
Based on the daily hail data at 175 stations in Beijing, Tianjin and Hebei Province (BTH for short hereinafter) during 1979 to 2008, using climate trend coefficient, trend rate, concentration degree (CD), concentration period (CP), and continuous power spectrum, the multiple timescale variation characteristics and trend variation of hail in BTH area are analyzed. It focuses on the four different key regions. Meanwhile, the significance of trend coefficient is tested by Monte Carlo scheme. The results show that the hail during last 30 years has increased obviously, the negative trend of hail is that reduction is larger in the northern areas than the southern areas, and larger in the mountain regions than the plain regions; there are 2.0-2.5 year periodic oscillations for interannual variations in all key regions, the interannual change of the occurring frequency of hail is characteristic of quasibiennial oscillation (QBO); The hailconcentration degree (HCD) in the southern area was the biggest, indicating that the time when hail occurred in this key region was relatively concentrated; The hailconcentration period (HCP) in all regions except southern area being in pentad 31 (about early June), was pentads 36-37， indicating that hail mainly occurred from late June to early July. Analysis on abrupt climate change using accumulated anomaly method and Yamamoto method shows that an abrupt decreasing occurred in 1993, especially in mountain regions.
2012, 38(2):197-203.
DOI: 10.7519/j.issn.1000-0526.2012.02.008
Abstract:
By using the radar of Longyan CINRAD/SA from 2003 to 2008 and Tlnp data， the environmental conditions of historical hail in southeastern Fujian and thunderstorm and gale weather in Western Fujian were analyzed and the CINRAD/SA products’ discriminant indices of historical hail weather and thunderstorm and gale weather in Southeastern Fujian were statistically established. Utilizing discriminant equations, CINRAD/SA products and Tlnp data, we carry out the strong convective weather nowcasting and the research of warning methods. First, we set up Fisher discriminant equations, which are mainly used to identify hail weather. Then we set up the second Fisher discriminant equations, which are mainly used to identify thunderstorm and gale weather. Through the hindcast of historical process and the 2009 trial forecast, it is shown that the forecast accuracy for hail weather system in southwestern Fujian is higher than that of the thunderstorm and gale weather in western Fujian. Using SCIT (storm cell identification and tracking) algorithm, the hail forecasting and validation were statistically tested, results showed that the SCIT method forecasts accurately and it can be used to forecast the storm moving speed and direction.
By using the radar of Longyan CINRAD/SA from 2003 to 2008 and Tlnp data， the environmental conditions of historical hail in southeastern Fujian and thunderstorm and gale weather in Western Fujian were analyzed and the CINRAD/SA products’ discriminant indices of historical hail weather and thunderstorm and gale weather in Southeastern Fujian were statistically established. Utilizing discriminant equations, CINRAD/SA products and Tlnp data, we carry out the strong convective weather nowcasting and the research of warning methods. First, we set up Fisher discriminant equations, which are mainly used to identify hail weather. Then we set up the second Fisher discriminant equations, which are mainly used to identify thunderstorm and gale weather. Through the hindcast of historical process and the 2009 trial forecast, it is shown that the forecast accuracy for hail weather system in southwestern Fujian is higher than that of the thunderstorm and gale weather in western Fujian. Using SCIT (storm cell identification and tracking) algorithm, the hail forecasting and validation were statistically tested, results showed that the SCIT method forecasts accurately and it can be used to forecast the storm moving speed and direction.
2012, 38(2):204-209.
DOI: 10.7519/j.issn.1000-0526.2012.02.009
Abstract:
A snowstorm accompanied with thunder and lightning on November 9, 2009 was analyzed from its smallscale feature. Using observation data from wind profiler, microwave radiometer, automatic weather station, Doppler weather radar and satellite, the fine temporal and spatial structures of this snow case and the causes for the convection in winter were discussed. The results showed that this case is a typical return flow process in northern China. The elevated convection and lightning storms were generated with the warm and moist air from southwest above the lower cold air, and the triggering mechanism for the convection was the disturbance in the middle layer. The results of this case study will be instructive for the winter lightning forecast in snowstorm weather.
A snowstorm accompanied with thunder and lightning on November 9, 2009 was analyzed from its smallscale feature. Using observation data from wind profiler, microwave radiometer, automatic weather station, Doppler weather radar and satellite, the fine temporal and spatial structures of this snow case and the causes for the convection in winter were discussed. The results showed that this case is a typical return flow process in northern China. The elevated convection and lightning storms were generated with the warm and moist air from southwest above the lower cold air, and the triggering mechanism for the convection was the disturbance in the middle layer. The results of this case study will be instructive for the winter lightning forecast in snowstorm weather.
2012, 38(2):210-219.
DOI: 10.7519/j.issn.1000-0526.2012.02.010
Abstract:
The height of the cloud base has significant effects on the global radiation balance and the aviation. In allusion to the merit and demerit of active and passive observations, a technique of spreading cloudbase height from CloudSat, using the MODIS classification, is advanced. Firstly, based on MODIS and CloudSat data, the method (CSAT) using satellite classification to extend the CloudSat data is compared with a traditional distanceweighted approach (MSAT) using regression analysis method. Then, the uniformity of cloud base over China and its neighborhood is analyzed. Eventually, using the statistic features of cloud base heights for different cloud types from CloudSat, a method combining the MODIS classification with distanceweighted to estimate cloudbase height is established and validated. The result indicates that the standard deviations of cloudbase height errors for all MODIS cloud types are totally less than 1.5 km, and the average values are also less than 1.5 km for all MODIS cloud types except cumulonimbus, of which the mean in the case of the distance between observed and predicted sites being greater than 400 km is slightly greater than 1.5 km.
The height of the cloud base has significant effects on the global radiation balance and the aviation. In allusion to the merit and demerit of active and passive observations, a technique of spreading cloudbase height from CloudSat, using the MODIS classification, is advanced. Firstly, based on MODIS and CloudSat data, the method (CSAT) using satellite classification to extend the CloudSat data is compared with a traditional distanceweighted approach (MSAT) using regression analysis method. Then, the uniformity of cloud base over China and its neighborhood is analyzed. Eventually, using the statistic features of cloud base heights for different cloud types from CloudSat, a method combining the MODIS classification with distanceweighted to estimate cloudbase height is established and validated. The result indicates that the standard deviations of cloudbase height errors for all MODIS cloud types are totally less than 1.5 km, and the average values are also less than 1.5 km for all MODIS cloud types except cumulonimbus, of which the mean in the case of the distance between observed and predicted sites being greater than 400 km is slightly greater than 1.5 km.
2012, 38(2):220-227.
DOI: 10.7519/j.issn.1000-0526.2012.02.011
Abstract:
The absorption of water by ambient aerosols and the influence of ambient relative humidity on the extinction coefficient are investigated under the assumptions that the atmosphere is in static stability during low visibility process caused by radiative cooling using the continuous observations data (visibility, relative humidity, temperature, wind etc.) from Shanghai Pudong automatic weather stations in 2009. The subtle features of meteorological elements are also studied with such high temporal resolution (1 min) data. The results show that the hygroscopic growth factor f(RH) of the extinction coefficient increased continuously with RH and featured a firstslowthenquick uptrend. The curves obtained from different seasons show that f(RH) was relatively higher in summer and autumn than that in winter and spring. Overall, the average f(RH) in 7 cases could reach to 6.6 when RH increased from less than 40% to 95%. We also present comparisons with other researches in the world, and the result shows that the behavior of the average of hygroscopic growth factor of the extinction coefficient in the cases is similar to the calculated growth factor of the scattering coefficient for ammonium sulfate. Further study also shows that the decrease of relative humidity is lagging about 1-2 hours behind the increase of temperature and visibility, which is conjectured that the humidity sensor fails to change quickly enough to measure the variation of relative humidity of the local air mass.
The absorption of water by ambient aerosols and the influence of ambient relative humidity on the extinction coefficient are investigated under the assumptions that the atmosphere is in static stability during low visibility process caused by radiative cooling using the continuous observations data (visibility, relative humidity, temperature, wind etc.) from Shanghai Pudong automatic weather stations in 2009. The subtle features of meteorological elements are also studied with such high temporal resolution (1 min) data. The results show that the hygroscopic growth factor f(RH) of the extinction coefficient increased continuously with RH and featured a firstslowthenquick uptrend. The curves obtained from different seasons show that f(RH) was relatively higher in summer and autumn than that in winter and spring. Overall, the average f(RH) in 7 cases could reach to 6.6 when RH increased from less than 40% to 95%. We also present comparisons with other researches in the world, and the result shows that the behavior of the average of hygroscopic growth factor of the extinction coefficient in the cases is similar to the calculated growth factor of the scattering coefficient for ammonium sulfate. Further study also shows that the decrease of relative humidity is lagging about 1-2 hours behind the increase of temperature and visibility, which is conjectured that the humidity sensor fails to change quickly enough to measure the variation of relative humidity of the local air mass.
2012, 38(2):228-233.
DOI: 10.7519/j.issn.1000-0526.2012.02.012
Abstract:
According to the common mode of production and the aim of research on watermelon in plasticcovered greenhouse in Dongtai, a meteorological station is built. Samples of both low temperature in the nighttime and high temperature in the sunny daytime are obtained respectively. After the data sequence is studied and analyzed, it is concluded that there is a close relationship between the temperatures in and outside the plasticcovered greenhouse at nighttime, and under the sunny conditions, the temperature inside has significant correlations with the external temperature, the solar altitude and the slant distance of sunlight through the atmosphere. Relationship, which is established by using the statistical regression analysis method, between the temperatures in and outside the greenhouse under both the cold conditions at nighttime and sunnyday conditions, has higher precision or reaches the practical precision. Low temperature ranges of alert levels at nighttime are defined with the temperature index of freezing injury and possibility. A tentative forecast is made on the time of occurrence of index temperatures inside the greenhouse in sunny days, and thus contributes to serve the watermelon production in plasticcovered greenhouse.
According to the common mode of production and the aim of research on watermelon in plasticcovered greenhouse in Dongtai, a meteorological station is built. Samples of both low temperature in the nighttime and high temperature in the sunny daytime are obtained respectively. After the data sequence is studied and analyzed, it is concluded that there is a close relationship between the temperatures in and outside the plasticcovered greenhouse at nighttime, and under the sunny conditions, the temperature inside has significant correlations with the external temperature, the solar altitude and the slant distance of sunlight through the atmosphere. Relationship, which is established by using the statistical regression analysis method, between the temperatures in and outside the greenhouse under both the cold conditions at nighttime and sunnyday conditions, has higher precision or reaches the practical precision. Low temperature ranges of alert levels at nighttime are defined with the temperature index of freezing injury and possibility. A tentative forecast is made on the time of occurrence of index temperatures inside the greenhouse in sunny days, and thus contributes to serve the watermelon production in plasticcovered greenhouse.
2012, 38(2):234-237.
DOI: 10.7519/j.issn.1000-0526.2012.02.013
Abstract:
Strong wind is one of the main meteorological disasters affecting the safety in transport and production in Xinjiang, especially in the Bailifengqu area (1.e. the strong wind regions along one hundred kilometer of railway). Because of special type of topography and geomorphy, Shisanjianfang Railway Station is a representative station where the wind is so strong and frequent. According to the narrow pipe effect of mountain pass and the theory of drainage winds after the cold air crosses the mountain, using the actual data measured in recent 2 years, the situations of strong wind appearance were estimated and validated in Bailifengqu area. The results show that in upstream the process of cold air invasion, there is a just 9-10 h delay correlation in wind velocity between upstream Mulei Station and downstream Shisanjianfang Station.
Strong wind is one of the main meteorological disasters affecting the safety in transport and production in Xinjiang, especially in the Bailifengqu area (1.e. the strong wind regions along one hundred kilometer of railway). Because of special type of topography and geomorphy, Shisanjianfang Railway Station is a representative station where the wind is so strong and frequent. According to the narrow pipe effect of mountain pass and the theory of drainage winds after the cold air crosses the mountain, using the actual data measured in recent 2 years, the situations of strong wind appearance were estimated and validated in Bailifengqu area. The results show that in upstream the process of cold air invasion, there is a just 9-10 h delay correlation in wind velocity between upstream Mulei Station and downstream Shisanjianfang Station.
2012, 38(2):238-243.
DOI: 10.7519/j.issn.1000-0526.2012.02.014
Abstract:
Based on the model output data, the synoptic verification of the mediumrange forecasting (larger than 72 h leading time）for T639, ECMWF and Japan operational models during the autumn of 2011 is conducted. The results show that the three models all have good performance on predicting the evolution of largescale circulation, such as zonal index and subtropical high. As a whole, the forecasting ability of ECMWF is the best among all models. Meanwhile, all the three models have good performance on forecasting of temperature at 850 hPa, especially over southern China. With respect to forecasting of typhoon Nesat, all the forecasted tracks lie east of the initial position, and its center pressure is larger than that of initial field. Although the forecasting stability is not so good, the forecast standard errors of ECMWF and Japan models are still comparatively small.
Based on the model output data, the synoptic verification of the mediumrange forecasting (larger than 72 h leading time）for T639, ECMWF and Japan operational models during the autumn of 2011 is conducted. The results show that the three models all have good performance on predicting the evolution of largescale circulation, such as zonal index and subtropical high. As a whole, the forecasting ability of ECMWF is the best among all models. Meanwhile, all the three models have good performance on forecasting of temperature at 850 hPa, especially over southern China. With respect to forecasting of typhoon Nesat, all the forecasted tracks lie east of the initial position, and its center pressure is larger than that of initial field. Although the forecasting stability is not so good, the forecast standard errors of ECMWF and Japan models are still comparatively small.
2012, 38(2):244-249.
DOI: 10.7519/j.issn.1000-0526.2012.02.015
Abstract:
The following are the main characteristics of the general circulation of atmosphere in November 2011: there is one polar vortex center in the Northern Hemisphere with the same strength as normal years. The circulation presents a fourwave pattern in middlehigh latitudes. The European trough is stronger and further east than the same period of normal years. The East Asian major trough is weaker and further east than the same period. This kind of circulation is not favorable for the outbreak of cold air southward. There are five cold surge processes affecting China, and the monthly mean temperature is 3.9℃，which is 1.8℃ higher than the same period of normal years. In this month, the southern branch trough is strong and the subtropical high is to west, which is favorable for transportation of the southwest warmmoist air to China. There are 6 main precipitation processes, and the mean precipitation (28.3 mm) is 57.3% above normal, which is the most in the past 20 years. The precipitation over most parts of the northern China is more than the same period of normal years, among them the precipitation over east of Northwest China, south of Inner Mongolia, west of North China, southeast of the Jiangnan region, centraleastern of South China is over three times more than the same period of normal years.
The following are the main characteristics of the general circulation of atmosphere in November 2011: there is one polar vortex center in the Northern Hemisphere with the same strength as normal years. The circulation presents a fourwave pattern in middlehigh latitudes. The European trough is stronger and further east than the same period of normal years. The East Asian major trough is weaker and further east than the same period. This kind of circulation is not favorable for the outbreak of cold air southward. There are five cold surge processes affecting China, and the monthly mean temperature is 3.9℃，which is 1.8℃ higher than the same period of normal years. In this month, the southern branch trough is strong and the subtropical high is to west, which is favorable for transportation of the southwest warmmoist air to China. There are 6 main precipitation processes, and the mean precipitation (28.3 mm) is 57.3% above normal, which is the most in the past 20 years. The precipitation over most parts of the northern China is more than the same period of normal years, among them the precipitation over east of Northwest China, south of Inner Mongolia, west of North China, southeast of the Jiangnan region, centraleastern of South China is over three times more than the same period of normal years.
2012, 38(2):250-256.
DOI: 10.7519/j.issn.1000-0526.2012.02.016
Abstract:
The radar VAD wind is restricted in data comprehensive operational application by without pressure information. To make up the disadvantage, this paper proposes a method to retrieve the pressure for VAD wind based on the surface meteorological information. The method introduces a polytrophic atmosphere into the pressurealtitude formula, in which the surface information is obtained from the automatic surface weather observation at the radar station. The temperature lapse rate is the most important influence on the estimation accuracy. It is calculated in changing with height, month, and region by 2007 radiosonde data. Then four different temperature lapse rate sensitive experiments are undertaken respectively: (1) constant， (2) time changing， (3) height changing， and (4) both time and height changing. Meanwhile, the climate statistic experiment is also done. The results of experiments indicate that the way based on surface observation reduces the error obviously compared with the traditional climate statistic way. Especially the heighttime dependent temperature lapse rate is better than other kind of temperature lapse rate. The spatial applicability of the method is evaluated too. The result reveals that the method has high applicability in different areas over China.
The radar VAD wind is restricted in data comprehensive operational application by without pressure information. To make up the disadvantage, this paper proposes a method to retrieve the pressure for VAD wind based on the surface meteorological information. The method introduces a polytrophic atmosphere into the pressurealtitude formula, in which the surface information is obtained from the automatic surface weather observation at the radar station. The temperature lapse rate is the most important influence on the estimation accuracy. It is calculated in changing with height, month, and region by 2007 radiosonde data. Then four different temperature lapse rate sensitive experiments are undertaken respectively: (1) constant， (2) time changing， (3) height changing， and (4) both time and height changing. Meanwhile, the climate statistic experiment is also done. The results of experiments indicate that the way based on surface observation reduces the error obviously compared with the traditional climate statistic way. Especially the heighttime dependent temperature lapse rate is better than other kind of temperature lapse rate. The spatial applicability of the method is evaluated too. The result reveals that the method has high applicability in different areas over China.
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ISSN:1000-0526 CN:11-2282/P