Rain Attenuation of Radar Echoes Considering Finite-Range Resolution and Using Drop Size Distributions

Abstract

The classical rain attenuation correction scheme of Hitschfeld and Bordan (HIBO) and the newer iterative approach by Hildebrand (HL) are reconsidered. Although the motivation for the HL algorithm was an extension into ranges, where HIBO tends to be unstable, it is shown here that the contrary is the case. The finiterange resolution causes an intrinsic instability of HL already at moderate attenuation, where HIBO would still deliver stable results. Therefore, the authors concentrate the further analysis on HIBO, and confirm that the usual implementation of HIBO does not account correctly for finite-range resolution. They suggest a modified scheme that produces exact retrievals in the ideal case of perfect measurements.For vertically pointing Doppler radars a new element is explored in the attenuation correction-namely, calculating rain attenuation k and rainfall R from Doppler spectra via the raindrop size distributions (RSDs). Although this spectral scheme (SIBO) avoids the uncertainty of Z-R and Z-k relations, the superiority of this approach is not a priori obvious because of its sensitivity to vertical wind. Therefore, radar rain rates, based on a Z-R relation and on RSDs, respectively, are compared with in situ measurements. The results indicate better agreement for RSD-based retrievals. Because k is closely correlated with R, the authors assert the advantage of RSD-based retrievals of k.The application of HIBO and SIBO to real data shows that the uncertainty of standard Z-R relations is the main source of deviation between the two versions. In addition, the comparison of profiles suggests that the parameters of Z-R relations aloft can deviate considerably from near-surface values. Although artifacts cannot be excluded with certainty, there is some evidence that this observation actually reflects microphysical processes.

Retrieval of the raindrop size distribution from polarimetric radar data using double-moment normalisation

“…MRR data were attenuationcorrected (METEK, 2010;Peters et al, 2010) and contained DSDs retrieved with vertical wind ignored (Strauch, 1976;Peters et al, 2002). Negative concentrations (METEK, 2010) in MRR DSDs were reset to zero.…”

Performance Evaluation of Micro Rain Radar Over Sumatra Through Comparison With Disdrometer and Wind Profiler

“…It is capable of resolving small drops and successful investigations using this radar have been reported in many literatures [25][26][27][28][29]. However, the accuracy of MRR has been questioned due to several problems such as strong rain attenuation at the frequency of 24.1 GHz [30] and the vertical wind that affects the fall speed of the drops [26], particularly in heavy rain. Thus, some correction techniques have been proposed to improve the MRR standard processing method [28,31].…”

“…The MRR installed at Kototabang has been overhauled by Meteorologische Messtechnik GmbH (Metek) and the firmware and software were replaced to the newest ones at that time. Thus, new attenuation correction scheme [30] may have been adopted to our instrument. The instrument is reinstalled in September 2011 and few results are published in a literature [9].…”

10th European Conference on Radar in Meteorology and Hydrology (ERAD 2018) : 1-6 July 2018, Ede-Wageningen, The Netherlands

“…But the rain intensity can attenuate significantly at moderate and higher rain rates, when the altitude is considered. To deal this problem, the attenuation correction is implemented follows the method discussed in detail by (Peters et al, 2010). Thus a loop for all height and all Doppler spectra is necessary to calculate the Path Integrated rain Attenuation denoted as PIA.…”