Improvement And Discussion Of Moisture Maximization In Estimation Of PMP

At present, Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) have been used as the main method to derive the designed flood of important water conservancy and Hydropower Engineering and nuclear power engineering, and they are also the important standard for reservoir dam and the spillway of universal design. Hydrological and meteorological experts at home and abroad have done a lot of work and got abundant accomplishment in the estimation of PMP and PMF.Probable maximum flood is based on the results of the probable maximum precipitation,so firstly, the status quo of research of PMP estimation method at home and abroad is introduced in this paper. Secondly, the principle and superiority of six estimation methods that now generally used are compared. Thirdly, three kinds of perceptible water calculation method are analyzed and compared, because those PMP estimation methods are based on perceptible water results. In the estimation of PMP, pseudo adiabatic method is usually used to estimate the perceptible water, while the world PMP industry generally believe that, if precipitable water is estimated by using this method, there may be bias. This study further found that this bias can be improved which is verified by the result of precipitable water of China mainland calculated by the pseudo adiabatic method. At last, case of PMP estimation of Hong Kong is discussed as an example of application of improved method in the estimation of PMP.Precipitable water of five provinces in the southeast coastal are calculated by using the sounding method, pseudo adiabatic method, and empirical formula method. And the results of all are so well correlated by comparison that could be used in calculation of precipitable water in practical work. The result of empirical formula method is smaller, while the pseudo adiabatic method is larger whose deviation changes with latitude that the relative error is bigger at lower latitudes. Therefore, if the storm transposition method is used to estimate PMP, latitude adjustment needs to be considered.Based on the analysis of climate conditions in Hong Kong, local rainstorm magnify method and improved storm transposition method are used to estimate the PMP of4hours and24hours in Hong Kong. The estimated PMP results are rationally analyzed in themselves and estimation methods.They are also compared with point rainstorm records in the southeast coastal China and world history, and the results of frequency analysis. It is believed that the estimated PMP results are reasonable by comprehensive analysis above and could be recommended for application in the engineering design.