JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG46] [EE] Satellite Earth Environment Observation / Satellite Based Remote Sensing of Weather, Climate, and Environment

Sun. May 21, 2017 9:00 AM - 10:30 AM 104 (International Conference Hall 1F)

convener:Riko Oki(Japan Aerospace Exploration Agency), Allen A Huang(University of Wisconsin Madison), Gail Skofronick Jackson(NASA Goddard Space Flight Center), Yoshiaki HONDA(Center for Environmental Remote Sensing, Chiba University), Paul Chang(NOAA College Park), Chairperson:Gail Jackson(NASA Goddard Space Flight Center)

9:30 AM - 9:45 AM

[ACG46-21] DSD database for the GPM/DPR precipitation retrieval algorithm

★Invited papers

*Shinta Seto1, Natsuki Iwama1, Kenta Miyazaki2, Toshio Iguchi3 (1.Graduate School of Engineering, Nagasaki University, 2.School of Engineering, Nagasaki University, 3.National Institute of Information and Communications Technology)

Keywords:GPM, DPR, drop size distribution

Rain Drop Size Distribution (DSD) has been and is being measured with disdrometers at many stations in the world. Parameterization of DSD is necessary for retrieving rain rates (R) from radar measurements. The relation between radar reflectivity factor (Z) and R (Z-R relation) is an example of DSD parameterization.
In the precipitation retrieval algorithm of the Dual-frequency Precipitation Radar (DPR) of the Global Precipitation Measurement (GPM) mission core satellite, the relation between the mass-weighted mean drop size (Dm) and R (R-Dm relation) is used. As both R and Dm are independent of radar frequency, R-Dm relation is useful in the dual-frequency algorithm and it may be extended for other radar measurements.
The standard R-Dm relation in the DPR algorithm was derived from Z-R relation which Kozu et al. (2009) proposed based on precipitation measurements in Tropics. It may not be appropriate and need to be modified for mid- and high-latitude precipitation within the DPR coverage.
In the DPR algorithm, at each pixel, R-Dm relation is modified by the Surface Reference Technique (SRT), while the SRT does not work well for light precipitation. However, dual-frequency measurements make it possible to adjust R-Dm relation for light precipitation.
The figure shows estimates of R and Dm for over-land convective precipitation cases by single-frequency (SF) algorithm (Fig. a) and dual-frequency (DF) algorithm (Fig. b) in the version-4 DPR algorithm. For weak precipitation, SF algorithm mostly follows the standard R-Dm relation, but DF algorithm gives larger Dm estimates.
Based on DF estimates, optical R-Dm relations are calculated for seasons and regions. They are summarized as DSD database. The new R-Dm relations are used for SF algorithm in the version-5 DPR algorithm (Fig. c). As a result, SF and DF algorithms give closer Dm for weak precipitation. As the next step, the DSD database needs to be validated and improved with ground-based measurements.