Analysis of a Precipitation System that Exists above Freezing Level Using a Multi-Parameter Phased Array Weather Radar

Abstract

An X-band multi-parameter phased array weather radar (MP-PAWR) was developed in 2017. The scan concept of the MP-PAWR is electronic scanning in elevation by combining fan beam transmissions and pencil beam receptions with digital beam-forming techniques and mechanical scanning along the azimuth. The MP-PAWR realized three-dimensional (60 km in radius and 15 km in height) observations without gaps of 30 s. Although the MP-PAWR is supposed to be suitable for observations of rapidly changing convective systems, it can be advantageous for observations of stratiform rainfall because of continuous vertical pointing observations and its ability to apply the Velocity Azimuth Display (VAD) method with a constant radius for a vertical profile of dynamic parameters such as divergence and deformation. In this study, a precipitation system that existed mainly above the freezing level (in this case, it was approximately 5 km in height) observed from 14:00 to 17:00 Japan Standard Time on 6 September 2018 was analyzed using MP-PAWR data. The averaged area of the vertical profile of Z, and the Doppler velocity with fixed elevation showed a stationary structure with time. The average differential reflectivity factor (ZDR) profile with fixed elevation angles showed values that were close to zero and increased with height. Similar characteristics were shown in the average Specific Differential Phase (KDP) profile. Vertical pointing data, especially for Z, ZDR, and Doppler velocity, were utilized when the echo passed over the radar site, and the Doppler velocity showed the acceleration of fall speed below the freezing level. The vertical profile of divergence with a fixed radius was calculated using the VAD method, and the vertical velocity was calculated using the fall speed profile from the vertical pointing data and by assuming the vertical velocity at the cloud base was zero. The results indicate that the updraft region corresponds to higher ZDR and KDP regions.

Validation of X-band multi-parameter phased array weather radar by comparing data from Doppler weather radar with a parabolic dish antenna

“…There are two main advantages of obtaining observations from dual-polarization weather radars: 1) rain attenuation can be corrected using the specific differential phase K dp (Smyth and Illingworth 1998;Bringi et al 2001;Park et al 2005a,b;Anagnostou et al 2006;Snyder et al 2010) and 2) hydrometeor classification can be made using the fuzzy logic approach, which is well suited to this type of radar (i.e., Liu and Chandrasekar 2000;Straka et al 2000;Lim et al 2005). Therefore, to improve the performance of the PAWR, an X-band multiparameter phasedarray weather radar (MP-PAWR) with a dual-polarization observation capability was developed and installed in the Kanto region of Japan in December 2017 (Takahashi et al 2019;Takahashi 2019;Kikuchi et al 2020a). The MP-PAWR is expected to improve observation accuracy using dual-polarization observations, rapid scanning, and high-density observations for use in making short-term weather predictions of rapidly developing cumulonimbus clouds.…”