A Study On Rainstorm And Its Objective Forecasting Methods In Ningxia Area

In the paper we studied rainstorm from1961to2013in Ningxia, by using rainstorm data of Ningxia25stations form1961to2013and automatic meteorological station data from2007to2013, and also based on NCEP/NCAR mean daily reanalysis data sets. Based on the conventional observation data, MICAPS data, NCEP/NCAR mean daily reanalysis data sets, the four rainstorm processes in Ningxia on July13,2006and July22-24,2010and July29,2012and July8,2013are diagnostic analyzed by using synoptic principles and synoptic analysis method.In the study it was showed that:1.Climate characteristics of Ningxia was studied in the paper, and then it’s obviously that Ningxia southern rainfall is more than northern,what means "South more and North less". The prone area of precipitation lie at the south to Zhongwei and at the east to HeLan Mountain.And the distribution of heavyrain multipolar is multipolar. From1961to2013there are three rainstorm concentration period, and it’s being more and more rainstorm occurred after2000,which mainly appeared in southern Ningxia and Yinchuan campagna.2.It’s obviously that rainstorm in Ningxia is concentrated from July to September every year,of which regional and monthly distribution characteristics are very obvious. Short-time rainstorm of Ningxia mainly occurred in the period which from16:00to02:00everyday,which is very consistent with daily variation of temperature.And it’s also has obvious interdecadal and interannual variation and low frequency oscillation characteristics of Ningxia rainstorm by using Mexihat wavelet.3.The principal influence systems are subtropical high, the Tibetan high, westerly trough,low vortex,shear line and upper and lower jet stream. The subtropical high provides water vapor and latent hear energy; the Tibetan high provides mechanism of upper divergence which strengthens the secondary vertical circulation; the low-lever southwest jet provides moisture condition and strong dynamic lifting condition for the rainstorm processes.4.It’s studied that there are three models of Ningxia rainstorm,which are grouped from34Ningxia rainstorm process by using SOMs space analysis method. Three models are long wave trough model, Straight flow model and two high converging attack model.5. It’s also showed that mid-low-leve high humidity areas are built before rainstorm,and zone of saturation are built while rainfall strengthening occuer.The necessary condition of Ningxia rainstorm is that700hPa RH=80%and the condition of heavy rainstorm is that700hPa RH=90%. There are obvious water vapor channel and transport during every rainstorm process in Ningxia.6.It’s showed that some indices are very useful for the rainstorm prediction,for example as SI index or LI index.7.On the basis of above research,16main factors and some index for Ningxia rainstorm forecast were selected, and then objective forecasting modeles with the physical index system for rainstorm was established, and the flow chart was given.8.Under the forecast model we tried to forecast the four rainstorm processes which happened in2006,2010,2012,2013,and then we tested forecast results. Test results showed that, these objective forecasting methods has some prediction ability on rainstorm in Ningxia,which forecasting TS was71.1%,and the dismissal rate and the false rate is not high. So these forecasting methods still need be improved in the future research.