Study On Precipitation Echo And Non-precipitation Echo Recognition Of Weather Radar

Doppler weather radar can provide us three basic products such as reflectivity, velocity and spectral width. Furthermore, other derivative products also could be obtained after algorithm introduced. The accuracy of product depends on the production algorithm and quality of base-data. Radar echoes can be devided into precipitation echoes and non-precipitation echoes. Some non-precipitation echo such as abnormal propagation (AP) echo can have considerable impact on the quality of radar data, Moreover, some helpful weather evidence can be received from other echo like clear air echo (CAE). So identification and classification of echoes are necessary and important. This paper is mainly focus on radar echo classification, and after recognition algorithm introduced, we can classify echo into clear air echo (CAE), abnormal propagation (AP) echo, stratiform echo and convective echo.The algorithm in this paper is based on the horizontal and vertical structure characteristics of different echo. By considering the statistics properties of several parameters, we are able to find out that the horizontal structure and texture of reflectivity, echotop and vertical gradient are helpful to echo recognition. In order to get echotop and vertical gradient Consistent with the echo, the echo top is derived from the actual height of 5dBZ by linear interpolating between more than and less than 5dBZ elevations; and the vertical gradient is obtained from the slope of vertical profile by using least squares linear fitting.For identifying the echo type, we should compare the parameters with certain threshold along with a proper order. The first step is classifying the echo into precipitation echo and non-precipitation echo (preliminary by echo top), the next step is conducted to make a distinction among stratiform precipitation, convective echo, CAE and AP echo by other parameter.To test and verify the identification algorithm, two "one hour precipitation (OHP)" calculate from the data have been compared before and after quality control respectively. By comparing the two OHP map, the fake precipitation of CAE and AP echo is removed after quality control introduced.