Study of Different Attenuation Correction Methods in Association with Rainfall Estimation for X-Band Polarimetric Radars

Different attenuation correction methods for the X-band dual linear polarimetric radar are analyzed in this paper. The specific differential phase shift KDP is always considered as an effective factor in radar signal attenuation correction. However, the values of KDP for light rains are too small, which results in unstable quality and large errors of rainfall estimation. Therefore, radar horizontal reflectivity ZH and specific differential phase shift are combined together in the ZH-KDP method to correct the attenuation error. Based on the similar consideration, a ZH-KDP-R combined technique is also proposed to estimate rainfall (R). During the development and set-up of the synchronous transmitting and receiving dual polarimetric Doppler weather radar with 3.2 cm wave length, a set of observational data were obtained in the field experiment in Pingliang, Gansu Province in August 2005. Some continuous measurements with 5-12-minute intervals were gained in the time period from 1508 to 2205 (Beijing Time) 11 August 2005. Using the data, the performance of the combined attenuation correction and rainfall estimation methods is examined. The results indicate that the ZH-KDP combined method is effective and the correction speed meets the requirement of real-time operations. The analysis of the precipitation process shows that the ZH-KDP-R combined technique is more suitable for rainfall estimation than single factor methods such as the KDP-R or Z-R relation, and the estimated results are in good agreement with automatic rain gauge records. As to the Z-R relation, the deviation between the precipitation estimation and the available gauge measurement decreases obviously when the corrected ZH is used, indicating that the radar data quality has been obviously improved after the attenuation correction.