Rainfall Estimation from C-Band Polarimetric Radar in Okinawa, Japan: Comparisons with 2D-Video Disdrometer and 400 MHz Wind Profiler

Abstract

This paper presents an inter-comparison of rainfall parameters (median volume diameter and rain rate) using C-band polarimetric radar, a 2D-video disdrometer and a 400 MHz profiler for the Baiu front event of 8-9 June 2005 in Okinawa, Japan. These instruments are part of the Okinawa Sub-Tropical Environment Remote Sensing Center, operated by the National Institute of Information and Communications Technology (NICT). The 2D-video disdrometer is used to derive the mean axis ratio of raindrops versus drop diameter, as well as the drop size distribution for the Baiu event. The data are then used to simulate various relations between polarimetric scattering parameters such as: specific attenuation ðA h Þ, and specific differential attenuation ðA dp Þ, versus specific differential phase ðK dp Þ which are required to correct the measured reflectivity at horizontal polarization ðZ h Þ, and the differential reflectivity ðZ dr Þ for rain attenuation. The 2D-video disdrometer data are also used to arrive at retrieval formulas for median volume diameter ðD o Þ from radar Z dr , and rain rate from radar K dp .The These inter-comparisons demonstrate the accuracy of C-band polarimetric radar to retrieve important rainfall parameters, as well as the accurate correction for rain attenuation using differential propagation phase.

Statistical Characteristics of Raindrop Size Distribution in the Meiyu Season Observed in Eastern China

“…The results show that DSDs are different from those observed in some other tropical or subtropical locations even though eastern China is situated in a similar latitudinal belt. For instance, compared to Darwin, Florida (e.g., Bringi et al 2003;Thurai et al 2010), and Japan (e.g., Bringi et al 2006;Marzano et al 2010), the NW value reported here is slightly lower. This is likely associated with local atmospheric aerosols and/or moisture.…”

“…The mean Dm and log10NW values are 1.40 mm and 3.55, respectively (4900 mm −1 m −3 for NW). These values are slightly lower as compared with those obtained in a Baiu front event in Okinawa, Japan (Bringi et al 2006; values are 1.47 mm for Dm and 6000 mm −1 m −3 for NW). The NW̶Dm pair for the whole dataset (denoted by black diamond in Fig.…”

“…Previous studies (e.g., Bringi et al 2006;Shusse et al 2009) have shown that Baiu events show stratiform and convective precipitation. In general, intense (weak) rainfall is generated by convective (stratiform) rain.…”

One decade of imaging precipitation measurement by 2D-video-distrometer

“…only some recent ones shall be mentioned, all of them published within 2005: Attenuation and crosspolar discriminations were studied by with a discussion on drop oscillations given by . Intercomparisons regarding drop size distributions, rainfall rates and derived radar reflectivities, involving data from different instruments, were carried out by Bringi et al (2005) and Kanofsky et al (2005). A climatological analysis based on 2DVD data is presented by Schuur et al (2005).…”

“…Intercomparisons regarding drop size distributions, rainfall rates and derived radar reflectivities, involving data from different instruments, were carried out by Bringi et al (2005) and Kanofsky et al (2005). A climatological analysis based on 2DVD data is presented by Schuur et al (2005).…”