Abstract:A two layer quasi geostrophic model forced by surface friction and radiative relaxation is used to study numerically the phenomenon of subcritical instability in baroclinic atmosphere.The numerical experiments show that when nondimension parameter β≥0.25,the phenomenon of subcritical instability can exist in two layer baroclinic atmosphere.The occurrence of subcritical instability is relative to the selection of the initial disturbances in model.The latitudinal gradient of Coriolis parameter is also an important factor that affects the strength of baroclinic stability,the larger its value is,the smaller strength of the baroclinic stability is.

Abstract:Analysis on the storm rainfall in Wuhan from 08:00 to 14:00 on July 22,1998 illustrates that the process,with the background of an ascending branch of subtropical meridional circulation,is independent of south warm area and north cold air.Low inflow air and high outflow air play an important part in the forming and maintaining of the large scale rain region.The heavy rain is directly resulted from up and low coupling of boundary layer southerly jet,low westerly jet and high westerly jet.Southerly jet at 925hPa is the chief provider of water vapor and trigger of convective instability energy release;moreover,low westerly jet at 850hPa contributes much to the forming and maintaining of convective instability at middle and low level,while mid latitude high westerly jet to the forming and maintaining of symmetrical instability at high level.The storm comes into being owing to coupling of the three jets which develop and strengthen the convective and ascending air movement at mid low level.

Abstract:By the use of 1873-1995 monthly mean Northern sea level pressure defined is the north Atlantic oscillation index(INAO).Studies of the relation of the winter I NAO to the climate of winter and summer over China by using the data for the last 45 years show that the winter I NAO anomaly bears a close relation to the mainland weather/climate of winter and summer.When a strong I NAO occurs China will experience an extensive high temperature and more rainfall in winter,and the summer temperature will be markedly lower in the band between the Yangtze and Huaihe River.Besides,the Northern surface and 500hPa winter and summer circulation features for the years of the strong and weak I NAO are studied and the results indicate that for strong I NAO years,the subtropical high and Siberian high as well as meridional circulation intensity in winter are greatly reduced in vigor with a weak WA teleconnection pattern and feeble east Asian winter monsoon.But the east Asian monsoon will be stronger in the following summer.

Abstract:A simple method to estimate the daily range of surface temperature is presented by using daily arbitrary time NOAA AVHRR Graph data based on the soil temperature equation which can express the daily variation of soil temperature.Particularly,the method can be applied in the calculation of inverse soil moisture so that when the both times of maximum and minimum temperatures are not consistent with the times that are required by thermal inertia method,this method can approximately estimate the daily range of surface temperature and can calculate thermal inertia of surface and soil moisture.In this paper,the feasibility is demonstrated using real cases.

Abstract:Moist potential vorticity is used to investigate the influence of the blocking high position in mid high latitude of east Asia on the path of cold air action and thereby on the location of torrential rain in China in July,1998.Results show that when the blocking high lies in the middle of Siberia(the sea of Okhotsk),the torrential rain will likely occur in north and south China(western part of NE China,north China and Sichuan Plain);When the high is in Xiaoxin'anling and the subtropical high is north of its mean position,NE China will be likely suffered from torrential rain;when the high lies over the area centered at 55°N,135°E,the cold air action will be more frequent in the mid low reaches of the Yangtze River with the torrential rain there.

Abstract:A possible cause of Typhoon 9408 abnormal track formation is diagnosed in the context of NCEP/NCAR reanalyses,indicating that the environmental steering flow,quasi homogeneous and dipole flows jointly exert significant effects on the abrupt changes in direction and velocity.

Abstract:A technique for detecting fog during daytime by the use of a combination of VIS and IR1 images from GMS 5 weather satellite is presented in this paper.This technique,combined with the analysis of texture characters,movement laws and dissipation laws of fog and low stratus,can be used to distinguish fog from low stratu clouds.A case study is given to demonstrate the effect and potential of this method.

Abstract:The δ¹³C time series obtained from trees in the Tianmu Mountains of Zhejiang Province contain high frequency variations and a long term decrease trend .By removing the long term decrease trend related to the δ¹³C variation with atmospheric CO₂,it is found that the high frequency variation is determined by the precipitation.Relation between the precipitation and the δ¹³C is analysed using PCA in terms of precipitation data in east China.The multiple regression method is employed to reconstruct the historical precipitation in east China,with a view to analyze the climatic change of centuries and evolution trend.

Abstract:This paper analyses barotropic vorticity,barotropic enstrophy,baroclinic vorticity and baroclinic enstrophy of the blocking in Okhotsk in 1998 by the use of barotropic and baroclinic decomposition.The results are as the follows:At the different stages of blocking,barotropic vorticity and enstrophy are far more than baroclinic vorticity and enstrophy,and both have different evolutional feature.At the developing stage,vorticity and enstrophy(including barotropic and baroclinic) increase instably and spread southwestward.At the maintaining stage,vorticity and enstrophy of barotropic and baroclinic reach maximum when blocking has built and stayed at the blocking field.At the decaying stage barotropic vorticity and enstrophy and baroclinic vorticity and enstrophy decrease instably and spread southeastward and the blocking disppeared.

Abstract:On the basis of the sowing experiment for Pei'ai64S conducted in Nanjing,Wuhan,Changsha,Guiyang and Sanya,the photo thermo character of development and fertility of Pei'ai64S was analyzed ,the light temperature level classifying and quantitive model of fertility methods were used to obtain fertility Index.The results of two methods were consistent well.

Abstract:A practical air pollution model is developed in this paper.This model includes modified two dimension Mass model whose forcasted wind field can be adjusted to the three dimensional wind field with the observed mean wind profile,and the three demensional Eulerian advection diffusion equation is solved by finite element method for atmospheric pollution.Based on these,forecast is made for the distribution of SO₂ concentration in Shanghai.Through half year experiments,the forecasted results show resemblance to the measured.So it can be used to practical forecast.Simulations show that the SO₂ high value area in Shanghai locates in Baoshan and urban area.In a day,SO₂ concentration is the highest in the morning,higher in the evening,the lowest at noon.

Abstract:Analysis of 1958-1997 NCEP/NCAR pentad dataset from April to June indicates that,the time when the average θ_se|850hPa≥335K and the negative zonal wind changes into positive stably in area(10-20°N,110-120°E) has a good correspondence with the onset date of South China Sea Summer Monsoon and can be used as a norm to judge the latter.Above condition should last at least 3 pentads and the following discontinuous time be less than 2 pentads,or last 2 pentads then has one pentad break then resume at once.

Abstract:The influence of climate on human body is a synthetic action of many meteorological elements.As usual,air temperature is used to be an index to indicate the warm and cool of environment,but the thermal regulation and thermal comfort of human body can not be assessed only by air temperature or other single meteorological element.The only way to describe the effects of the thermal environment on human body completely is to do by means of a heat balance model.In such model all relevant meteorological parameters,behavioral characteristics(activity and clothing) and body measurements can be considered.By the use of numerical weather forecast results and the model MEMI,the problems of heat balance and ways of solving them are described,and an new thermal indexthe physiological equivalent temperature of human body has been calculated to assess the thermal comfort.

Abstract:Based on the data obtained with a ground based dual channel microwave radiometer in Xining,Qinghai Province,during spring season in 1997,the total cloud water vapor(V) and cloud liquid water(L) are analyzed for different months and weather conditions.The results show that,for the specified weather conditions,the values of L increase gradually from March to May at a growth rate of 20-40% per month while the values of V have no significant variation.The cloud liquid water content is only about 1% of the water vapor content in the atmospheric column.Comparison of the observed data from the Tibetan Plateau with the data from Hebei Plain shows that there are no significant differences in the cloud liquid water content between these two areas,but the V over Xining is higher than that over Shijiazhuang by about 30%-50%.

Abstract:By the use of NCEP/NCAR reanalysis dekad sensible heat flux (SHF) dataset from 1979 to1995,the spatial and temporal distribution of SHF over the Asian monsoon region is investigated based on the Rotated Empirical Orthogonal Function(REOF).Results show that the variations of SHF in the Indian Peninsula and the Indochina Peninsula have strong connections to the onset and evolution of Asian monsoon,and these are probably the leading key regions for the monsoon onset.According to the seasonal variation of time coefficient,the accumulations of SHF over the Indian Peninsula and the Indochina Peninsula are probably one of the triggers of east Asian monsoon onset.Moreover,the sudden change of SHF over north of the Indian Peninsula during summer monsoon period probably plays an important role in the evolution of the Indian summer monsoon.In addition,the difference of SHF between the north of the Indian Peninsula and west of the Tibetan Plateau plays an important role in the onset and maintenance of Indian monsoon.However,the difference of SHF between Northeast Asia and Northwest Pacific has influence on the evolution of east Asian summer monsoon only but has no direct connection to winter monsoon.Above all,the forcing of SHF in the north of the Indian Peninsula and the northwest of the Tibetan Plateau plays a leading role in the onset of east Asian monsoon.

Abstract:A heavy snow case over the eastern Tibetan Plateau on Jan.16-18,1996 is studied by means of the Q vector,indicating that there exists convergence from 500hPa to 200hPa 24 hour ahead of the snow,and heavy snow may occur in the south of frontogenetical positive area(F) at 500hPa and correspond to positive center of Δ24θ_se field.

Abstract:The probability distribution of annual typhoon maximum wind speed in Shanghai is developed through the Monte Carlo simulation method.The 30 year and 50 year return period wind speed estimations are correspond to the observations.The results show that the annual probability distribution of typhoon maximum wind speed in Shanghai is reliable and the Monte Carlo method is a good tool for developing annual probability distribution of wind speed in coastlands where are prone to tropical cyclone each year.

Abstract:By defining the climate risk for seed breeding of two lines hybrid rice,on the basis of Jiangxi geographical data with scale of 1 to 250000,climate data in 40 years of 84 stations,and with the help of GIS spatial analysis method,climate risk division is done for seed breeding base of two line hybrid rice,the best region and season for seed breeding of different species can be assured.

Abstract:By establishing the following five dependent functions: feature of increasing output,feature of stabilizing output,importance feature,economy feature and drought resistance feature;and by using mathematical method Fuzzy,this paper calculates major planting crops' ecologic climate & economic superiority of Wuwei town,and shows that the most superior four planting crops in order are corn,sugar beet,cole and wheat under the present condition in society,nature and economy.Furthermore,on the basis of ecologic climate and economic superiority the adjustment suggestion for the present planting structure is proposed.

Abstract:Using the boundary layer adiabatic liquid equation of Boussinesq,compared is the vertical motion ordering of the one dimension jet stream gravitational wave of the boundary layer,and the development of the turbulence of the jet stream gravitational wave of the boundary layer is discussed,it is found that the jet stream gravitational wave of the boundary layer is one formation mechanism of the air turbulence.

Abstract:A model is established to predict winter precipitation in Hanoi by means of dynamic ARIMA model and SAS software.The possible effect on the forecasting of precipitation caused by the fluctuation of some variables in the climatic system is considered in the model.The model is assessed by 1996~1998 independent data.It is shown that computational results of model are generally consistent with the observation data.

Abstract:Modern blocking high theories are reviewed and summarized into five categories with a brief comment.The developing tendency of the blocking high is also addressed.