Abstract:Based on parameterization of cumulus and saturation moist static energy conservation principle in moist adiabatic process,by means of Clapeyron equation transformation,the cumulus parameters such as vapour of forming cumulus,the ratio of cumulus area and so on are calculated using partial realtime data and numerical weather forecast products.Furtherly,the convective precipitation is calculated by model.With empirical correction to the calculated value,the experimental forecast formula of convective precipitation is established,and the forecast result is quite good.

Abstract:Based on continuity of meteorological fields,a simple technique to analyse crosssection charts is proposed with the aid of results in Chen(1996).The technique has much more superiority and much better reliablity than the traditional,and is specially suitable to diagnose structure of weather systems.

Abstract:Based on the daily meteorological data in the recent 40-year and the flow-off data for more than one hundred,the climate features during the damming period in Sanxia area and the variabilities of the weather element,such as temperature,precipitation,wind and weather phenomenon,which would affect the engineering procedures,are analysed in detail.The statistical relationship between the streamflow at dam site during the damming period and precipitation for previous period in the upper reserivor area,and then the longterm forecast model of streamflow are established.

Abstract:The climatic features of the beginning time of flood seasons in the Sanxia reservoir region from 1961 to 1994 is analyzed in detail.The dates of the beginning time of flood seasons in the reservoir region are compared with those in the middle and lower reach of the Yangtze River.It is found that they are almost synchronous on the whole.In addition,the times and the spatialtemporal distribution of all kinds and levels of heavy rain in the reservoir region are investigated.The results show that the number of days of heavy rain in the eastern part of the region is more than those in the western part on average.

Abstract:The dates and atmospheric circulation patterns of the heavy rain in spring were investigated based on data during 34 years from 1961 to 1994.It is found that the firsttime heavy rains in spring mostly (about 80%) occur in April;two necessary conditions for the heavy rain are that:the synoptic depression system appears in east of Tibet Plateau and a cold air mass,which moves from Siberia,intrudes into the depression system.

Abstract:The Characteristics of heavy fog over Sanxia on Changjiang River and the optimum ensured ratio in period of damming the river or constrution are analysed based on the recent longterm data in Yichang station,which provided the important reference evidences for Sanxia Dam project.

Abstract:Based on 34 years daily meteorological data from Yichang station in Hubei Province,the low temperature condition and winter construction period of Sanxia dam area were analysed.The result shows that the low temperature days and winter construction period in Yichang exhibited very obvious interannual variation.This provides background for winter temperature prediction and preparation for the Sanxia Project.

Abstract:Using the monthly rainfall data in 89 stations in Northwest China from 1961 to 1990,the interannual and decadal change of precipitation are investigated.It is shown that in recent 30 years there exists a distinct increase of rainfall in June in this region.

Abstract:The characteristic of precipitation and atmosphere circulation for snow disaster over the eastern part of Tibetan plateau in winter 1995/1996 are analysed.Also the relationship between the climatic oscillation of the precipitation over the Tibet and atmosphere circulation background is discussed.The analysis result shows that there exists a tendency of increase of the snow disaster and precipitation in winter from 1960—1970 to 1980—1990.

Abstract:With dynamical analysis,the paper focuses the time and space condition and physics mechanism about the North Gulf depression strengthening to be tropical storm.The upper and lower situation characteristics and space structure are discussed.By means of calculation and analysis of diagnosis field,the results reveal the dynamical field and vapour distribution feature at levels.The viewpoint of the shortterm forecast of the North Gulf depression strengthening to be tropical storm is given.

Abstract:The univariate and bivariate regression analysis between the radar echo and the rainfall parameters of single cumulus is presented.The analyysis results show that correlations between amount,intensity and persistence of the precipitation and top high and area of the radar echo are well consistent.The precipitation estimates using the regression method are accurate,and the calculation is simple.

Abstract:Water is an important factor of influence on crop development.Based on the field experiments,the impacts of drought treatment with different timing on the crop development stages is studied.The experiment shows that the results are significant in the guidance of field irrigation,in the saving of water,in the regulation of crop development stages and in the improvement of crop yield and quality.