An Application of Composite Index Method to Precipitation Categorical Forecast

By using of the T106 analysis data of National Meteorological Center during January 1995-December 1997,factors grouped and correlation analysis the physical factors close correlation with precipitation and definitely differentiating precipitation were defined.Every factor in sample is arranged from low to high order,then divided in section,and calculated precipitation frequency in every section.According to every facter contribution to precipitation,the weighing coefficient of every factor was calculated.The precipitation frequency of every section of every facter of every sample are weighed,and then added.A composite precipitation frequency value is given by history sample fitting.The TS score maximum value of the precipitation is defined as composite forecast index.The composite index of short-range forecast about light rain,moderate rain,heavy rain and storm rain were derived respectively.Precipitation categorical forecasts were conducted by using the method and the forecast effect was analysed.

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