Abstract:In order to combine forecsts made with several methods with an optimizing forecast,a technique of combining forecast,which is called an optimal blending method,is suggested.The technique considers both a persistence forecast and systematic errors existing in the methods.A hindcast data the for years was established.Then a linear model was set up with the data set.The test for the precipitation field in summer(June,July,August) was conducted.It shows that the optimal blending method can improve the forecast skill significantly,but the skill varies year-to-year.

Abstract:By using a limited area operational forecasting model and choosing a precipitation weather process caused by a tropical storm in August 1998,comparative forecasting experiments of an improved mass-flux cumulus parameterization scheme taking into account the effects of both updrafts and downdrafts and the original one only includes updrafts used in the model were performanced.The results show that downdrafts contribute significantly to the improvement of the model precipitation forecasts for over 25.0mm.

Abstract:The radar installation,communication transmission,data flow through the system,product acquisition ways and radar adaptable parameters setting of the WSR-88D in Shanghai Meteorological Bureau were introduced.Three applicable samples in 1998 were analyzed.The results showed that the WSR-88D has a very strong detective ability for storms.It has played an important role in severe weather nowcasting through analysis of the storm structure and evolution of velocity field data.

Abstract:The composition and feature of data communication system in WSR-88D Doppler Weather Radar was summarized.The communication equipment allocation and an operational process design in Shanghai Site were introduced.The operating effect of the system was given.

Abstract:There are over 70 products(base and derived products) in the WSR-88D.Because of the limitation of communication and data archive,only part of the products can be shown at one time from Principal User Processor(PUP).Routine Product Set (RPS) plays an important role in product generation and distribution of WSR-88D.The principle and methods of RPS are discussed,and some RPS examples of Shanghai are given.

Abstract:By use of synoptic map,cloud image,sounding data and Doppler radar data,the heavy rain gust case which occurred in the 23th of July,1998 is analyzed.It suggests that MCS can be developed on the downwind of MCC under positive large scale environment,which results in heavy rain gust of Shanghai.Furthermore,according to the Doppler radar base reflectivity,radial velocity and VAD Wind Profile (VWP) data closely related to the developing,strengthening,moving and merging of heavy rain gust echo,the forming and developing of trigger mechanism such as meso scale shear or meso scale eddy was detected several hours ago.

Abstract:By use of Shanghai WSR-88D Doppler radar data,the characters of typhoon 9806 on the base reflectivity map and radial velocity map were analyzed,and in combination with these two kinds of data,the research on tracking location and practical application of typhoon 9806 was also conducted.

Abstract:The design and operation of WSR-88D Doppler weather radar hail algorithm were described,and the strengths and weakness of these algorithm were given.Finally,in order to improve the potential to detect and forecast severe hail an improved practical method which can be used in operation was suggested.

Abstract:The rain cluster,the radar echo,surface wind field (streamline field) and pressure field during torrential rain over Beijing area in July,1998 were analysed.The results show that there is an obvious mesoscale characteristic for torrential rain process.The mesoscale easterly shear line,the convergence line of wind velocity and the mesoscale depression system all played important role during the torrential rain events.

Abstract:Utilizing the precipitation and temperature data from 1951 to 1995 in Beijing,the spring drought indices applying for realtime operatinal monitoring for spring drought and the indices for the first soaking rain in spring are studied,their characteristics are analyzed and discussed.

Abstract:The Data of diurnal temperature range and the hourly mean termperature value collected and studied during 1989～1995 in Beijing.The hourly temperature forecast for different areas are calculated by using statistical method.This forecast has been applied on specialized weather service.The beneficial results are obtained.