Identification of Ground Clutter with C-band Doppler Weather Radar

The application of radar data is negatively affected by echoes caused by ground clutter, meanwhile these echoes from ground clutter have significant effect on rainfall estimation and radar data assimilation. As a result, it is important to identify and discriminate these echoes, which is an absolutely necessary part of radar data quality control. The ground clutter identifying algorithms in operation are mostly based on S-band Doppler weather radar, the resolution and velocity scanning mode of which are different from those of C-band radar. Few researches are carried out to discuss whether the method based on S-band is applicable to the C-band radar or not. Based on the current algorithm used for the SA radar, one method is developed for the CC radar using the data observed by radars of Changzhi and Harbin. The statistical characteristics of clutter are analyzed using data collected during 2011, and the membership functions are improved for C-band Doppler weather radar.Results show that, for S-band and C-band Doppler weather radar, parameters about reflectivity of ground clutter are similar, and there are notable differences between ground clutter and precipitation echoes. For C-band ground clutter echoes, the parameter T_DBZ is greater than S-band. G_DBZ value of both kinds of radar is alike, mostly below 0. S_PIN value of ground clutter echoes is remarkably greater than that of precipitation echoes for both C-band and S-band radar. It shows that three parameters about reflectivity including T_DBZ, G_DBZ and S_PIN, can be used to identify and discriminate C-band radar ground clutter echoes.For C-band radar ground clutter and precipitation echoes, only M_DVE, associated with velocity, could be used to distinguish these two kinds of echoes. For M_DSW and S_DVE, there is no notable difference between ground clutter and precipitation. In contrast, two parameters of ground clutter are different from that of precipitation echoes for S-band radar. For S-band radar, M_DSW and S_DVE are both very small, mostly below 1. There are considerable numbers of values above 1 for two parameters of C-band radar. The spatial resolutions of two kinds of radars are different, which may result in the fact that M_DSW and S_DVE could not be used to distinguish ground clutter echoes from precipitation echoes. Besides, the velocity scan mode, the dual pulse repetition frequency may cause the phenomenon to some extent. It can also be caused by the different precisions of two kinds of radars. The velocity precision of S-band radar is 0.5 m·s^-1, while the velocity of C-band radar is 0.1 m·s^-1. For S-band radar, the velocity changes more smoothly than that of C-band radar. Compared with the method based on S-band radar, the identification accuracy of ground clutter is improved notably and the false detection of stratiform cloud echoes is also reduced obviously.