Abstract: The K_DP value detected by dual-polarization Doppler radar plays an important role in measuring rainfall and classifying hydrometeor. The K_DP value was directly obtained from S band dual-polarization Doppler radar signal processor (RVP8) and its calculation process was not shown on the technical introduction, thus it was unfavourable to pretreatment and quality control of data. Three methods calculating K_DP values were summarized. According to the observational data, the K_DP values calculated by three methods were compared with those from signal processor (RVP8). The results indicate that the error of the K_DP value calculated by least square method is the minimum among the three models. The effects of different smoothness distances along the radar radial on the K_DP value with least square method are discussed. The relationship between the K_DP value detected by radar and precipitation intensity calculated by Z-R relationship is analyzed. It shows that the smoothness distance to 5 km could retain not only the enough smoothness effect but also the enough meteorological information. Moreover, it does not influence the measurement of precipitation. The relationship between the K_DP value and precipitation intensity is significant, especially in strong precipitation phase. Thus, the K_DP value could be used to estimate precipitation intensity.

Key words: Dual-polarization radar, Algorithm of K_DP, Reflectivity factor, Precipitation intensity