ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 33,Issue 1,2007 Table of Contents
2007, 33(1):3-10.
DOI: 10.7519/j.issn.1000-0526.2007.01.001
Abstract:
The current development on storm identification, tracking and forecast ing based on weather radar data are reviewed. Storm identification , tracking and forecasting, as the earliest nowcasting techniques, are the basic and essential parts of radar and severe weather warning operations. At present, they include three aspects: cross correlation algorithm, cell centroid cracking algorithm, persistence prediction method, which are called as extrapolation. Among t hem, Persistence prediction method has been replaced by the former two methods. Firstly, the history and main algorithms of cross correlation and cell centroid method are presented in detail. Secondly, a few new methods based on the extrapo lation are described. Finally, in combination with FDP project during Sydney Oly mpic Games, test and evaluation on nowcasting technique are also discussed.
The current development on storm identification, tracking and forecast ing based on weather radar data are reviewed. Storm identification , tracking and forecasting, as the earliest nowcasting techniques, are the basic and essential parts of radar and severe weather warning operations. At present, they include three aspects: cross correlation algorithm, cell centroid cracking algorithm, persistence prediction method, which are called as extrapolation. Among t hem, Persistence prediction method has been replaced by the former two methods. Firstly, the history and main algorithms of cross correlation and cell centroid method are presented in detail. Secondly, a few new methods based on the extrapo lation are described. Finally, in combination with FDP project during Sydney Oly mpic Games, test and evaluation on nowcasting technique are also discussed.
2007, 33(1):11-18.
DOI: 10.7519/j.issn.1000-0526.2007.01.002
Abstract:
It is very effective to improve new generation weather radar application that re liable 3D wind fields are retrieved from real time radar radial velocities. The retrieved wind field can help forecaster to identify the mesoscale structures. T he potential usage of 4DVAR assimulation technique with pure dynamical process t o retrieve wind field in real time is examined by using the Doppler radar data in Guangzhou and Jinan. It is argued whether the we t process needsto be input into cloud model, and what should iteration number, retrieval area, background and initial fields be, etc. In addition, the retrieva l results are analyzed from different aspects including wind field structure, co mputer time, mean square deviation etc. Tests show that there is little difference between retrieved results from th e dry and wet 4DVAR systems. Given a background field, the basic characteristi cs in lowlevel wind fields can be presented from dry model by 1520 iteration s, and model results are high sensitive to initial and background fields. Under the condition of background field, dry results iterated 1520 times can be effecti vely operated, which are beneficial to improve the accuracy of meso , micros cale weather system forecast.
It is very effective to improve new generation weather radar application that re liable 3D wind fields are retrieved from real time radar radial velocities. The retrieved wind field can help forecaster to identify the mesoscale structures. T he potential usage of 4DVAR assimulation technique with pure dynamical process t o retrieve wind field in real time is examined by using the Doppler radar data in Guangzhou and Jinan. It is argued whether the we t process needsto be input into cloud model, and what should iteration number, retrieval area, background and initial fields be, etc. In addition, the retrieva l results are analyzed from different aspects including wind field structure, co mputer time, mean square deviation etc. Tests show that there is little difference between retrieved results from th e dry and wet 4DVAR systems. Given a background field, the basic characteristi cs in lowlevel wind fields can be presented from dry model by 1520 iteration s, and model results are high sensitive to initial and background fields. Under the condition of background field, dry results iterated 1520 times can be effecti vely operated, which are beneficial to improve the accuracy of meso , micros cale weather system forecast.
2007, 33(1):19-24.
DOI: 10.7519/j.issn.1000-0526.2007.01.003
Abstract:
With the increasing of Automatic Weather Stations (AWS) of China Meteorological Administration (CMA), it is very vital for meteorological operation to develop and set up a quality control system of observations from AWS. As a qual ity control flow from observational station to provincial meteorological data de partment, subsequently to national data department, the threestep quality cont rol system in operation for observations from AWS has been studied since 2004. E ach step has automatic control technique and interface application technique, al lowing analyzing and amending some data. The threestep quality control system c ould improve the collection and disposition level of data observed at AWS and cou ld insure the data quality. The operational flow setting in the whole quality co ntrol system, the quality control technique and the quality control information have been presented.
With the increasing of Automatic Weather Stations (AWS) of China Meteorological Administration (CMA), it is very vital for meteorological operation to develop and set up a quality control system of observations from AWS. As a qual ity control flow from observational station to provincial meteorological data de partment, subsequently to national data department, the threestep quality cont rol system in operation for observations from AWS has been studied since 2004. E ach step has automatic control technique and interface application technique, al lowing analyzing and amending some data. The threestep quality control system c ould improve the collection and disposition level of data observed at AWS and cou ld insure the data quality. The operational flow setting in the whole quality co ntrol system, the quality control technique and the quality control information have been presented.
2007, 33(1):25-31.
DOI: 10.7519/j.issn.1000-0526.2007.01.004
Abstract:
In order to further understand the severe weather originating in the p eriphery of typhoons and improve the capability of severe weather potential fore cast and warning, the synoptic background, water vapor, CAPE, WI, vertical veloc ity and sea breezes are analyzed on a severe convection weather occurring in out er periphery of Typhoon Rananim in August 2004 based on the Doppler radar, autom atic weather station and NCAR/NCEP reanalyzed data etc. The continual heat wave in South China resulted from the subsidence from subtropical high and the periph ery of Typhoon Rananim, consequently, internal energy is accumulated，and strong instable state is established. When the subtropical high weakened and the subsidence disappeared a s a result of northwestward moving of Typhoon, the severe convection is triggere d by the weak trough and sea breeze and a dry line. The stabi lity outsides the typhoon is of fluctuant characteristics. The convection develo ped on an instable tongue with higher temperature and higher humidity that joint with the end of an exterior spiral cloud band of Typhoon Rananim. Wind Index is more available in forecasting thunderstorm wind gusts than other indexes in Sou th China.
In order to further understand the severe weather originating in the p eriphery of typhoons and improve the capability of severe weather potential fore cast and warning, the synoptic background, water vapor, CAPE, WI, vertical veloc ity and sea breezes are analyzed on a severe convection weather occurring in out er periphery of Typhoon Rananim in August 2004 based on the Doppler radar, autom atic weather station and NCAR/NCEP reanalyzed data etc. The continual heat wave in South China resulted from the subsidence from subtropical high and the periph ery of Typhoon Rananim, consequently, internal energy is accumulated，and strong instable state is established. When the subtropical high weakened and the subsidence disappeared a s a result of northwestward moving of Typhoon, the severe convection is triggere d by the weak trough and sea breeze and a dry line. The stabi lity outsides the typhoon is of fluctuant characteristics. The convection develo ped on an instable tongue with higher temperature and higher humidity that joint with the end of an exterior spiral cloud band of Typhoon Rananim. Wind Index is more available in forecasting thunderstorm wind gusts than other indexes in Sou th China.
2007, 33(1):32-37.
DOI: 10.7519/j.issn.1000-0526.2007.01.005
Abstract:
By use pentad precipitation data at 25 stations in Liaoning Province from 1960 to 2005, the characteristics of the spatialtemporal distribution and variation of the precipitation are analyzed，in terms of the precipitation conce ntration degree (PCD) and precipitation concentration period (PCP). Meanwhile, t he comparison of the PCD is also made between rainy years and dry years. The results show that the PCD and PCP can demonstrate the inhomogeneity of q uantitative precipitation in spatialtemporal distribution. The mean PCD in al l stations is 0.655, with the maximum of 0.749, and the minimum of 0.509. The mean of PCP is 40.953 pentad, with the maximum of 45.221 pentads, the minimum of 37 .697 pentads. The trend of both annual PCD and the PCD in flood season diminishe s. The diminishing trend of the PCD in flood season is obvious. The EOF of norma lized anomaly fields of the PCD shows that the three EOF modes can depict the sp atial distribution. The first principal component exhibits all the stations inph ase. The second principal component takes on seesaw between the southeast and no rthwest areas. The synthetic analysis of more and less precipitation showed that PCD in years with more precipitation is obviously larger than that of less prec ipitation, besides, the distribution of the PCD is more complicated in rainy yea rs than in dry years.
By use pentad precipitation data at 25 stations in Liaoning Province from 1960 to 2005, the characteristics of the spatialtemporal distribution and variation of the precipitation are analyzed，in terms of the precipitation conce ntration degree (PCD) and precipitation concentration period (PCP). Meanwhile, t he comparison of the PCD is also made between rainy years and dry years. The results show that the PCD and PCP can demonstrate the inhomogeneity of q uantitative precipitation in spatialtemporal distribution. The mean PCD in al l stations is 0.655, with the maximum of 0.749, and the minimum of 0.509. The mean of PCP is 40.953 pentad, with the maximum of 45.221 pentads, the minimum of 37 .697 pentads. The trend of both annual PCD and the PCD in flood season diminishe s. The diminishing trend of the PCD in flood season is obvious. The EOF of norma lized anomaly fields of the PCD shows that the three EOF modes can depict the sp atial distribution. The first principal component exhibits all the stations inph ase. The second principal component takes on seesaw between the southeast and no rthwest areas. The synthetic analysis of more and less precipitation showed that PCD in years with more precipitation is obviously larger than that of less prec ipitation, besides, the distribution of the PCD is more complicated in rainy yea rs than in dry years.
2007, 33(1):38-44.
DOI: 10.7519/j.issn.1000-0526.2007.01.006
Abstract:
With the establishment of radar network in the coastal area of China, r adar measurements are becoming an important monitoring method for approaching ty phoon especially before its landfall. An objective method to retrieve wind via t racing radar echo displacement is described in details and applied to the circul ation and intensity estimation of landing typhoons “Nari" and “Chebi" i n 2001. It is found that real wind distribution features can be captured effectively usin g CAPPI and PPI radar images by quality control with an accuracy equivalent to t he operational analysis.
With the establishment of radar network in the coastal area of China, r adar measurements are becoming an important monitoring method for approaching ty phoon especially before its landfall. An objective method to retrieve wind via t racing radar echo displacement is described in details and applied to the circul ation and intensity estimation of landing typhoons “Nari" and “Chebi" i n 2001. It is found that real wind distribution features can be captured effectively usin g CAPPI and PPI radar images by quality control with an accuracy equivalent to t he operational analysis.
2007, 33(1):45-50.
DOI: 10.7519/j.issn.1000-0526.2007.01.007
Abstract:
MICAPS data and NCEP 2.5°×2.5°reanalysis data during the period of 199 6—2005 are used to make statistical research on the activity of southwest vorte x and floodproducing vortex influencing South China. The climatic features such as frequency of vortex activity, genesis, movement track, and intensity during t he genesis and moving process, and its lifetime, average circulation field, and precipitation features are investigated. And the allocation of influencing flood producing synoptic system and its model graph are offered to provide basis for forecasting vortex and floodproducing heavy rainfall in South China.
MICAPS data and NCEP 2.5°×2.5°reanalysis data during the period of 199 6—2005 are used to make statistical research on the activity of southwest vorte x and floodproducing vortex influencing South China. The climatic features such as frequency of vortex activity, genesis, movement track, and intensity during t he genesis and moving process, and its lifetime, average circulation field, and precipitation features are investigated. And the allocation of influencing flood producing synoptic system and its model graph are offered to provide basis for forecasting vortex and floodproducing heavy rainfall in South China.
2007, 33(1):51-56.
DOI: 10.7519/j.issn.1000-0526.2007.01.008
Abstract:
In order to improve thunderstorm potential forecast ability, on the basis of sta tistics and analysis of thunderstormforming weather conditions in Anhui Provin ce, the convection parameters were selected from the T213 data during 2 003 to 2004 as forecast factors. By considering the seasonal variation character istics of the factors, the thunderstorm trend is forecasted with the discriminat ion analytical method and index accumulation method. The result indicates that t he latter method excels the former. Finally, the index accumulation method was u sed to forecast the thunderstorm from March to August in 2005, the result is tha t Critical Success Index (CSI) is 69.4%, Percent Of Doom (POD) is 89.5%, False Alarm Rate (FAR) is 24.4%, and the accuracy of regional forecast is b etter. Besides, regional hail and thunderstorm with strong wind during the testing period are all forecasted correctly. It is obvious that this method has better indicative significance to forecast the hail and thunders torm with strong wind.
In order to improve thunderstorm potential forecast ability, on the basis of sta tistics and analysis of thunderstormforming weather conditions in Anhui Provin ce, the convection parameters were selected from the T213 data during 2 003 to 2004 as forecast factors. By considering the seasonal variation character istics of the factors, the thunderstorm trend is forecasted with the discriminat ion analytical method and index accumulation method. The result indicates that t he latter method excels the former. Finally, the index accumulation method was u sed to forecast the thunderstorm from March to August in 2005, the result is tha t Critical Success Index (CSI) is 69.4%, Percent Of Doom (POD) is 89.5%, False Alarm Rate (FAR) is 24.4%, and the accuracy of regional forecast is b etter. Besides, regional hail and thunderstorm with strong wind during the testing period are all forecasted correctly. It is obvious that this method has better indicative significance to forecast the hail and thunders torm with strong wind.
2007, 33(1):57-61.
DOI: 10.7519/j.issn.1000-0526.2007.01.009
Abstract:
It is influenced by the weather climate that how many early rice shou ld be sowed,so peasants have difficulty to make dicision. In order to help the p easant to solve this difficult problem, the classified forecast quota decisionma king method was adopted according to the meteorological information, the prod uction cost and so on, the peasant was provided the most superior sowing s eeds quantity decisionmaking, the obvious economic efficiency can be obtaine d in the practical application.
It is influenced by the weather climate that how many early rice shou ld be sowed,so peasants have difficulty to make dicision. In order to help the p easant to solve this difficult problem, the classified forecast quota decisionma king method was adopted according to the meteorological information, the prod uction cost and so on, the peasant was provided the most superior sowing s eeds quantity decisionmaking, the obvious economic efficiency can be obtaine d in the practical application.
2007, 33(1):62-69.
DOI: 10.7519/j.issn.1000-0526.2007.01.010
Abstract:
The general differences of the geopotential height, temperature and w ind fields between the NCEPFNL and the T213L31 analysis datasets from May 11 t o June 10,2005 are analyzed. The results indicate that the biases at lower laye r of atmosphere are minimum and the maxima often appear in 3 key regions. By usi ng a correlation analysis of biases of terrain height and geopotential height, t he bias of terrain height over the QinghaiTibetan Plateau is regarded as the m ajor force to form the bias of geopotential height between two datasets. Besides , the impacts of the biases on atmospheric circulation at middle and lower layer s are compared and illustrated. The results indicate that the Southwest Vortex a nd the heat source of the plateau in former dataset are stronger than that of th e latter and the shear of wind speed is weak.
The general differences of the geopotential height, temperature and w ind fields between the NCEPFNL and the T213L31 analysis datasets from May 11 t o June 10,2005 are analyzed. The results indicate that the biases at lower laye r of atmosphere are minimum and the maxima often appear in 3 key regions. By usi ng a correlation analysis of biases of terrain height and geopotential height, t he bias of terrain height over the QinghaiTibetan Plateau is regarded as the m ajor force to form the bias of geopotential height between two datasets. Besides , the impacts of the biases on atmospheric circulation at middle and lower layer s are compared and illustrated. The results indicate that the Southwest Vortex a nd the heat source of the plateau in former dataset are stronger than that of th e latter and the shear of wind speed is weak.
2007, 33(1):70-73.
DOI: 10.7519/j.issn.1000-0526.2007.01.011
Abstract:
The downburst on June 25, 2006 in central part of Shaanxi Province was analyzed with Doppler radar data from Xi’an. The results show that the strong single cell is combined and enhanced to cause a bow echo, leading to the weather with strong wind 33 m·s-1. The height of reflectivity factor core (60dBz ) drops markedly. The vertical column liquid water content is 70kg·m-2. The convergence in the middlelevel of the bow echo is relatively strong. The characteristi cs of convergence in the middle level of Doppler wind field can be seen clearly.
The downburst on June 25, 2006 in central part of Shaanxi Province was analyzed with Doppler radar data from Xi’an. The results show that the strong single cell is combined and enhanced to cause a bow echo, leading to the weather with strong wind 33 m·s-1. The height of reflectivity factor core (60dBz ) drops markedly. The vertical column liquid water content is 70kg·m-2. The convergence in the middlelevel of the bow echo is relatively strong. The characteristi cs of convergence in the middle level of Doppler wind field can be seen clearly.
2007, 33(1):74-80.
DOI: 10.7519/j.issn.1000-0526.2007.01.012
Abstract:
A squall line event on 28 April 2006 in Shandong Province was diagnos ed. The developing mechanism of the squall line was studied with the moist poten tial vorticity conservation theory. The results show that the squall line was ca used by 500hPa trough. The lowlevel temperature and humidity increasing, the c old air behind upper trough moving toward east and south and the low energy tongu e located above high energy tongue caused atmospheric convective instability. The air convergence and rising motion produced by shear line at 850hPa and the l ow pressure trough on the ground triggered convective instable energy release so a s to produce convective cloud cell which moved east and developed under the environment conditions of atmospheric thermal instability and strong vertical wind shear, thus forming a squall line. The lowlevel atmospheric moist baroclinity increasing destroye d geostrophic wind balance and resulted in slant vorticity developing, rising mo tion increased and convection came into being. Highlevel high potential vortic ity transporting downwards caused the lowlevel potential vorticity to increase , and to bring about vertical vorticity to increase. All the above factors are p ropitious to lowlevel mesoscale vorticity to develop so that convection increa sed. The interaction between strong rising movement and strong vertical wind she ar accelerated convection to develop and form squall line, and cause thunderstor ms and gales.
A squall line event on 28 April 2006 in Shandong Province was diagnos ed. The developing mechanism of the squall line was studied with the moist poten tial vorticity conservation theory. The results show that the squall line was ca used by 500hPa trough. The lowlevel temperature and humidity increasing, the c old air behind upper trough moving toward east and south and the low energy tongu e located above high energy tongue caused atmospheric convective instability. The air convergence and rising motion produced by shear line at 850hPa and the l ow pressure trough on the ground triggered convective instable energy release so a s to produce convective cloud cell which moved east and developed under the environment conditions of atmospheric thermal instability and strong vertical wind shear, thus forming a squall line. The lowlevel atmospheric moist baroclinity increasing destroye d geostrophic wind balance and resulted in slant vorticity developing, rising mo tion increased and convection came into being. Highlevel high potential vortic ity transporting downwards caused the lowlevel potential vorticity to increase , and to bring about vertical vorticity to increase. All the above factors are p ropitious to lowlevel mesoscale vorticity to develop so that convection increa sed. The interaction between strong rising movement and strong vertical wind she ar accelerated convection to develop and form squall line, and cause thunderstor ms and gales.
2007, 33(1):81-86.
DOI: 10.7519/j.issn.1000-0526.2007.01.013
Abstract:
With the TBB data from FY-2C satellite and the hourly observed precip itation data，the TBB features of torrential rain causing flood in Sout h China from 18 to 22 June,2005 are studied．The results show that TBB can direc tly and quantitatively present the features of the intensity and distribution of the cloud sys tem with heavy rainfall. The torrential rainfall area is basically in the lower TBB band. The rainfall intensity increases when TBB decrease s. The daily variation of the rainfall intensity is in accord with that of TBB．The strong southwest monsoon plays a key role in the development and enhancement of the strong conve ctive cloud cluster in South China.
With the TBB data from FY-2C satellite and the hourly observed precip itation data，the TBB features of torrential rain causing flood in Sout h China from 18 to 22 June,2005 are studied．The results show that TBB can direc tly and quantitatively present the features of the intensity and distribution of the cloud sys tem with heavy rainfall. The torrential rainfall area is basically in the lower TBB band. The rainfall intensity increases when TBB decrease s. The daily variation of the rainfall intensity is in accord with that of TBB．The strong southwest monsoon plays a key role in the development and enhancement of the strong conve ctive cloud cluster in South China.
2007, 33(1):87-93.
DOI: 10.7519/j.issn.1000-0526.2007.01.014
Abstract:
The operation of AREM2.3 in Wuhan Institute of Heavy Rain, CMA, in the flood season of 2005 is steady. The TS scores of the precipitation forecast are calcul ated in various areas, such as, the middle and lower reaches of the Changjiang R iver, South China, North China, Northeast China, Southwest China and Hubei Provi nce in flood season (June, July and August). The fail rate, false rate, predicti ng deviation of the whole China in flood season are calculated.The comparison b etween the forecast and real rain field is made. And the TS scores of important rainfall processes of those areas are calculated. The evaluation of the model prediction is made by comparin g with the persistent forecast. It indicates that th e prediction of AREM2.3 in the flood season of 2005 is steady in 48 hours, and A REM2.3 has relative high prediction ability for rain in the middle and lower rea ches of the Changjiang River, South China, North China, Northeast China, Southwe st China, Hubei Province and the whole China, but the prediction for heavy rain centers is not perfect, AREM2.3 has high prediction ability for meteorological e lements in highlevel, too, its predicting ability for 500hPa height is better than that for 500hPa temperature.
The operation of AREM2.3 in Wuhan Institute of Heavy Rain, CMA, in the flood season of 2005 is steady. The TS scores of the precipitation forecast are calcul ated in various areas, such as, the middle and lower reaches of the Changjiang R iver, South China, North China, Northeast China, Southwest China and Hubei Provi nce in flood season (June, July and August). The fail rate, false rate, predicti ng deviation of the whole China in flood season are calculated.The comparison b etween the forecast and real rain field is made. And the TS scores of important rainfall processes of those areas are calculated. The evaluation of the model prediction is made by comparin g with the persistent forecast. It indicates that th e prediction of AREM2.3 in the flood season of 2005 is steady in 48 hours, and A REM2.3 has relative high prediction ability for rain in the middle and lower rea ches of the Changjiang River, South China, North China, Northeast China, Southwe st China, Hubei Province and the whole China, but the prediction for heavy rain centers is not perfect, AREM2.3 has high prediction ability for meteorological e lements in highlevel, too, its predicting ability for 500hPa height is better than that for 500hPa temperature.
15 Weather System Types of Aircraft Artificial Precipitation
Enhancement in Autumn in Gansu Province
2007, 33(1):94-98.
DOI: 10.7519/j.issn.1000-0526.2007.01.015
Abstract:
To investigate features of the autumn weather system over Gansu Provin ce in airplane artificial precipitation enhancement, statistical analysis was co nducted， based on the data of airplane artificial precipitation enhancement ope rations from 1991 to 2002. Meanwhile, discriminant model of the autumn weather s ystem of Gansu was established by utilizing the information of sounding data and the autumn weather system features. The results show that upper air circulation of the autumn precipitation in Gansu can be divided into three categories i.e. straight and fluctuant flow pattern, southwest flow pattern and northwest flow p attern. Among those patterns, the straight and fluctuant flow pattern occurred m ore frequently than other two patterns.
To investigate features of the autumn weather system over Gansu Provin ce in airplane artificial precipitation enhancement, statistical analysis was co nducted， based on the data of airplane artificial precipitation enhancement ope rations from 1991 to 2002. Meanwhile, discriminant model of the autumn weather s ystem of Gansu was established by utilizing the information of sounding data and the autumn weather system features. The results show that upper air circulation of the autumn precipitation in Gansu can be divided into three categories i.e. straight and fluctuant flow pattern, southwest flow pattern and northwest flow p attern. Among those patterns, the straight and fluctuant flow pattern occurred m ore frequently than other two patterns.
2007, 33(1):99-106.
DOI: 10.7519/j.issn.1000-0526.2007.01.016
Abstract:
Using the observational data provided by MICAPS, the characteristics of the moist potential vorticity of two abrupt torrential rain events in Guanzho ng, Shaanxi on June 29, 2004, and in northern Shaanxi on August 10, 2004 are ana lyzed. The results show that at 700 hPa level, the generation of a mesoscale c onvective instable area with MPV1≤-0.3 PVU and a mesoscale convective stab le area with MP1≥0.3 PVU at the upper stream, is favorable for moist barotropi c features, and contributes to the occurrence of abrupt torrential rains. The favorabl e moist baroclinic features develop at 700hPa level, while the plateau trough mo ves eastwardsto Hetao area or Guanzhong area. A moist baroclinic center with MPV 2＜0 generates at the rear of the trough, as a moist baroclinic center with t he MP2＞0 is in front of the trough. The positive and negative moist barocl inic centers above rainfall location and its neighboring upper stream, form an isoline concentrated zone of MPV2, which coupled with the mesoscale convective i nstable center with MPV1≤-0.3 PVU accords to the rainfall location. On MPV 1 zonal crosssection chart, an MPV column, nearly through upper and low levels, builds up in westtilting with height at neighboring upper stream of the rainfall location before the Guanzhong torrential rain. While at Ansai, a funnellike positive MPV extends from upper level down to the lower troposphere, which overlaps the nega tive MPV area developing in the boundary layer. The deep negative MPV la yer develops above the rainfall location. Simultaneously, at the midlow level of tropo sphere, the positive MPV column moves eastwards to the rainfall location to f orm a steep isolineconcentrated zone of MPV, which holds indicative meaning to theoccurrence of abrupt torrential rains. The MPV disturbance owns the characte ristic of spreading from high to low latitudes. Its threedimensional structure and evolution are the useful information in predicting abrupt torrential rain occurr ing in the eastern Tibetan Plateau.
Using the observational data provided by MICAPS, the characteristics of the moist potential vorticity of two abrupt torrential rain events in Guanzho ng, Shaanxi on June 29, 2004, and in northern Shaanxi on August 10, 2004 are ana lyzed. The results show that at 700 hPa level, the generation of a mesoscale c onvective instable area with MPV1≤-0.3 PVU and a mesoscale convective stab le area with MP1≥0.3 PVU at the upper stream, is favorable for moist barotropi c features, and contributes to the occurrence of abrupt torrential rains. The favorabl e moist baroclinic features develop at 700hPa level, while the plateau trough mo ves eastwardsto Hetao area or Guanzhong area. A moist baroclinic center with MPV 2＜0 generates at the rear of the trough, as a moist baroclinic center with t he MP2＞0 is in front of the trough. The positive and negative moist barocl inic centers above rainfall location and its neighboring upper stream, form an isoline concentrated zone of MPV2, which coupled with the mesoscale convective i nstable center with MPV1≤-0.3 PVU accords to the rainfall location. On MPV 1 zonal crosssection chart, an MPV column, nearly through upper and low levels, builds up in westtilting with height at neighboring upper stream of the rainfall location before the Guanzhong torrential rain. While at Ansai, a funnellike positive MPV extends from upper level down to the lower troposphere, which overlaps the nega tive MPV area developing in the boundary layer. The deep negative MPV la yer develops above the rainfall location. Simultaneously, at the midlow level of tropo sphere, the positive MPV column moves eastwards to the rainfall location to f orm a steep isolineconcentrated zone of MPV, which holds indicative meaning to theoccurrence of abrupt torrential rains. The MPV disturbance owns the characte ristic of spreading from high to low latitudes. Its threedimensional structure and evolution are the useful information in predicting abrupt torrential rain occurr ing in the eastern Tibetan Plateau.
17 Climatic Change and Its Impact on Water Resources in Jinzhong，
Shanxi Province for Recent 49 Years
2007, 33(1):107-111.
DOI: 10.7519/j.issn.1000-0526.2007.01.017
Abstract:
Based on the climate and water resources data of Jingzhong , Shanxi Pr ovince for recent 49 years, the change characteristics of temperature, precipita tion and water resources are analyzed. The results indicate that the annual mea n temperature is rising at a rate of 0.3 ℃/10a, and the increasing mainly occur s in winter. While, the precipitation is decreasing at a rate of 35.9mm/10a, wit h the largest decrease in the 1990s. The water resources, groundwater and river runoff all tend to decrease, which are consistent with the changes of precipitat ion.
Based on the climate and water resources data of Jingzhong , Shanxi Pr ovince for recent 49 years, the change characteristics of temperature, precipita tion and water resources are analyzed. The results indicate that the annual mea n temperature is rising at a rate of 0.3 ℃/10a, and the increasing mainly occur s in winter. While, the precipitation is decreasing at a rate of 35.9mm/10a, wit h the largest decrease in the 1990s. The water resources, groundwater and river runoff all tend to decrease, which are consistent with the changes of precipitat ion.
2007, 33(1):112-117.
DOI: 10.7519/j.issn.1000-0526.2007.01.018
Abstract:
Based on the monthly temperature data at 7 stations in Gannan, Gansu Province, the variation characteristics of temperature in recent 40 years were a nalyzed. The results show that the abrupt change of the annual mean temperature occurred in the early of 1990s, the nighttime temperature increased in the end of 1980s, in the 1990s the temperature of daytime and nighttime increased co ncurrently, the main reason for the abrupt change of temperature in the area is co ncurrent increase of the daytime and nighttime temperature in the 1990s. It is found that a quasi8year period is the main period of the mean temperature, maximum temperature and minimum temperature before the mid 1980s. The mean tempera ture of autumn began increasing from the end of 1980s, the mean temperatures of summer and winter began increasing from the early of 1990s.The daily maximum tem perature, daily minimum temperature and daily range of temperature vary with sea sons.
Based on the monthly temperature data at 7 stations in Gannan, Gansu Province, the variation characteristics of temperature in recent 40 years were a nalyzed. The results show that the abrupt change of the annual mean temperature occurred in the early of 1990s, the nighttime temperature increased in the end of 1980s, in the 1990s the temperature of daytime and nighttime increased co ncurrently, the main reason for the abrupt change of temperature in the area is co ncurrent increase of the daytime and nighttime temperature in the 1990s. It is found that a quasi8year period is the main period of the mean temperature, maximum temperature and minimum temperature before the mid 1980s. The mean tempera ture of autumn began increasing from the end of 1980s, the mean temperatures of summer and winter began increasing from the early of 1990s.The daily maximum tem perature, daily minimum temperature and daily range of temperature vary with sea sons.
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