Research On Retrieval Of GPS Water Vapor And Method Of Rainfall Forecast

Flood is regarded as one of the most frequent and the most severe nature disaster over the world wide and short -term rainfall prediction and advanced technology should be applied in order to improve forecast precision and new methods for prediction should be explored in every field. Research on Retrieval of GPS Water Vapor and Method of Rainfall Forecast are keen field which draws all attention from wide world.The dissertation is accomplished on the basis of Sino-Italy Collaborative Project-'The integral system of flood risk programming, monitoring and real time forecasting" and the primary achievements and conclusion reached include:(1) A reasonable design has been made for GPS water vapor monitoring networkAccording to the theory of GPS satellite signal propagation and vertical distribution of water vapor and local synoptic characteristic of Binjiang basin, the effective area where water vapor can be detected by GPS station has been determined under different cut-off angles. The conclusion has been reached that 3~4 GPS receivers are enough for water vapor monitoring in Binjiang basin. After having carried out the field survey and studied the constructive experience of GPS integrated application network in Shanghai and the Umbria basin GPS network in Italy, the reasonable design has been made for GPS water vapor monitoring network in Binjiang basin.(2) Model correction and comparisonIn the process of conversion from zenith day delay to GPS water vapor and precision evaluation. Saastamoinen(SA) model and Hopfield(H) for dry delay and Bevis model for atmospheric weighted temperature are adopted. However, the profile of temperature and humidity is variable in real atmosphere so that the optimum result for GPS water vapor may not be achieved by those popular models in our country. The paper have built the local correction models for dry delay and atmospheric weighted temperature and have made a comparison between two models for calculating actual water vapor on the basis of actual upper-air detecting data. AH results show that the conclusion is satisfied.(3) The optimized strategy analysis on retrieval of GPS water vaporThe optimized strategy analysis on retrieval of GPS water vapor has been carried out under different data processing schemes by using GPS observation. The parameters selection problem has been resolved in GPS water vapor retrieval process such as the optimum number of adopted IGS stations, the relation between single station processing and united station processing, network layout, cut-off angle, zenith delay parameter, period, knot position and so on.(4 ) Research on ANN model joined with GA for area rainfall forecastThe method is taken to join the genetic algorithm(GA) and BP algorithm together and supplementing mutually by optimizing the initial weights of ANN with GA, and some application has been made in the Binjiang basin for precipitation forecast. The ANN model by GA has been established which forecast variables are selected by optimized subclass regression technique and the optimized ANN model for basin area precipitation has been obtained. The experiment result of ANN model joined with GA for area rainfall forecast shows that this method can enhance the forecast precision of 6-hoursprecipitation compared with other statistical methods, and its effectiveness and the reliability of the method has been proved.(5) Parameterization of infrared satellite cloud imagery and its application in rainfall predication Obvious correlation exist between the probability of rain and parameterization estimate such as average brightness temperature(tb), brightness temperature variance(f), equivalent cloudage (CN),brightness temperature area index(Al-the first A5-the fifth grade, A6-the sixth grade). The statistical result shows that the average precision of rainfall intensity is over 80% which varies largely with rainfall intensity grades using infrared cloud imagery parameters and the size of analysis field has slight effect on it.The monthly model make less improvement on p...