126 Error Analysis of Regional Radar-gauge Synchronously Integrated Precipitation Estimation Equation

Thursday, 29 September 2011
Grand Ballroom (William Penn Hotel)
Yufa Wan, China Meteorological Administration, Wuhan, Hubei Province, China; and J. Wang and H. Jin

Research is focused on the error from ABS regional radar precipitation estimation equation (Wan et al., 2010). It is pointed out that the presence of μi misestimate factor of single station is the fundamental reason for radar precipitation estimation error. This misestimate factor is caused by the relative bias between ABi (from single station observation) and ABS (common coefficient from the whole region). Two important evaluation criterions for precipitation estimation on radar covered region are developed and their analytic expressions are given based on μi. The first criterion is the regional precipitation misestimate ratio μS, which is defined as the ratio of the sum of every single station's misestimate value (positive or negative) and the sum of the corresponding station's observed precipitation in the whole region. The misestimate ratio μS is used to evaluate the estimation error of the regional precipitation gross. The second criterion is the regional precipitation absolute misestimate ratio μ|S|, which is given by the ratio of the sum of every single station's misestimate absolute value and the sum of the corresponding station's observed precipitation in the whole region. The absolute misestimate ratio μ|S| is used to evaluate the gross absolute estimation error of the region and is the most widely used criterion for precipitation estimation error. The value of μ|S| indicates the general polymerization and dispersion degree of ABi from ABS of every station within the area S . Under the different raingauge network conditions of basic network, intensive network and grouping network, the difference and variance of μ|S| during one same rain event is analyzed. It is revealed that due to the nonuniform distribution of ABi (the transform coefficient of ZB-QG relationship on single station) in natural rainfall, the change in the estimated area S and its domain, raingauge network distribution and its density will all lead to different values of μ|S|. This is the uncertainty of precipitation estimation error during radar-raingauge integration. In this paper a new data pair quality control method is proposed called single station misestimate factor μi control method. This method will decrease the dispersion degree of ABi from ABS and increase the polymerization degree, thus the regional precipitation absolute misestimate ratio μ|S| is diminished accordingly. Experimental evaluations from Wuhan radars during four rain events give a value μ|S| of less than 30%, which is a 3-5% decrease compared with none quality control.
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