Precipitation Estimation And Extrapolation Forecast Based On The Radar Data Quality Control

The weather radar has important significance in disastrous precipitation measurement of meso-microscale with high space-time resolution.Compared to raingauges, radar rainfall estimation had obvious advantages, but the quality of radar data have impact on the accuracy of rainfall estimation. Therefore, the quality control of radar data should be taken in order to obtain more accurate rainfall estimattion.For the purpose of decreasing the effect of non-precipitation echoes and bright band on surface rainfall estimation, Radar reflectivity three-dimensional structure characteristic was presented to distinguish precipitation and non-precipitaion echoes removed afterwards,and then the stratiform and convective clouds were distinguished respectively from precipitation echoes. The VPR of stratiform clouds were constructed by averaging the layered reflectivies at near range to identify the height and depth of bright band. Both the curvature feature of VPR and the high area of echoes on PPI and VCS disappeared after the bright band reflectivities were corrected.On the base of quality control of radar reflectivity factor, TREC vector field was calculated by using extend corrected (Tracking Radar Echo by Correlations) TREC technique to extrapolate radar reflectivity factors and obtain extrapolative hourly rainfall with the corresponding Z-I relationship. The comparative analysis between predicted values and actual values show that the predicted values overestimated and were still closest to the actual value in 0-10mm,,and the ruslts were opposite when predicted values were above 10mm. Then the raingauge data were used to evaluate the accuracy of hourly rainfall. Result show that precision evaluation index of mixed clouds were better than that of stratiform and convective clouds, the extrapolative hourly rainfall were closer to raingauge data and the correlation coefficient reaches 0.6737. The forecast accuracy of relatively small thershlods were much better than that of larger values. Because the radar rainfall estimation was based on the relationship between Z and I, using radar echo after quality control as the extrapolation parameter has certain indication to precipitation nowcasting.