Development of synthetic GPM/DPR data from TRMM/PR and evaluation of GPM/DPR level-2 “at-launch” algorithms using them

The JAXA-NASA Joint Algorithm Team has developed the Level 2 (L2) algorithm for Dual-frequency Precipitation Radar (DPR) onboard the Global Precipitation Measurement (GPM) core observatory, which provides estimated precipitation rate, radar reflectivity factor, and precipitation information. The synthetic DPR Level 1 (L1) data is necessary as a test bed of the DPR L2 algorithms. In this study, synthetic DPR L1 data estimated from the TRMM/PR data are produced in 7 orbits during 15th March 2007 and 32 orbits during 31st Mar. to 1st Apr. 2011. The at-launch codes of L2 Ku, L2 Ka, L2 DPR algorithms (Version 4.20130328) were applied to the L1B synthetic data. The Ku/Ka/DPR products are compared with the PR products. Precipitation rates at 2km altitudes of Ku-L2 estimates are similar to those of the PR 2A25 product. Correlation coefficients are 0.93 and 0.81 over ocean and land, respectively. On the other hand, underestimation in Ka-L2 estimates and overestimation in DPR-L2 estimates are found in precipitation rate more than 4mm/hr over ocean.