GPM Satellite Simulator Over Ground Validation Sites

Toshihisa Matsui


The Global Precipitation Measurement (GPM) Mission Core satellite will be launched in February 2014. It will provide next-generation satellite rainfall measurement after 15 years of successful operation of the Tropical Rainfall Measuring Mission (TRMM) satellite. While TRMM has significantly improved the quantitative estimation of tropical rainfall (37 latitude), GPM will extend spaceborne precipitation measurements to high latitudes (65 latitude), where light precipitation and snowfall frequently occur. For this, the GPM Core satellite carries a combination of active and passive microwave sensors with improved capabilities to detect light rain and falling snow. The GPM Dual-frequency Precipitation Radar (DPR) includes Ka-band (35.5GHz) radar reflectivity measurements in addition to Ku-band (13.6GHz) measurement similar to the TRMM Precipitation Radar (PR). The GPM Microwave Imager (GMI) includes high-frequency sounder channels (166~183GHz) in addition to imager channels (10~89GHz) similar to the TRMM Microwave Imager (TMI). These sensor upgrades require more complex precipitation algorithms to estimate warm/cold/mixed-phase precipitation rate over various precipitation regimes.

Prior to the Core Observatory launch, the “day-one” GPM operational precipitation algorithms and their associated products must be tested using proxy data to demonstrate their validity. To this end, we have developed the Synthetic GPM Simulator and algorithm testbeds. The Synthetic GPM Simulator is a framework that integrates the GPM Ground Validation (GV) observations, the regional high-resolution storm simulation with an explicit microphysics model (WRF-SBM), and a unified GPM instrument simulator (G-SDSU). Essentially, GV in-situ observations were compiled to constrain the storm simulations, then constrained simulation is eventually used to predict GPM-observable signals through the unified GPM simulator. The simulated GPM orbital testbed are used to diagnose the performance of pre-launch precipitation algorithm for upcoming launch of the GPM Core Observatory. This seminar provides the highlight of the researesearch related to the Synthetic GPM Simulator project, and its applications and limitation/uncertainties are discussed.