Evaluation of Heavy Precipitation Simulated by the WRF Model Using 4D-Var Data Assimilation with TRMM 3B42 and GPM IMERG over the Huaihe River Basin, China

Lu Yi,Wanchang Zhang,Kai Wang

doi:10.3390/rs10040646

Abstract

To obtain independent, consecutive, and high-resolution precipitation data, the four-dimensional variational (4D-Var) method was applied to directly assimilate satellite precipitation products into the Weather Research and Forecasting (WRF) model. The precipitation products of the Tropical Rainfall Measuring Mission 3B42 (TRMM 3B42) and its successor, the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM IMERG) were assimilated in this study. Two heavy precipitation events that occurred over the Huaihe River basin in eastern China were studied. Before assimilation, the WRF model simulations were first performed with different forcing data to select more suitable forcing data and determine the control experiments for the subsequent assimilation experiments. Then, TRMM 3B42 and GPM IMERG were separately assimilated into the WRF. The simulated precipitation results in the outer domain (D01), with a 27-km resolution, and the inner domain (D02), with a 9-km resolution, were evaluated in detail. The assessments showed that (1) 4D-Var with TRMM 3B42 or GPM IMERG could both significantly improve WRF precipitation predictions at a time interval of approximately 12 h; (2) the WRF simulated precipitation assimilated with GPM IMERG outperformed the one with TRMM 3B42; (3) for the WRF output precipitation assimilated with GPM IMERG over D02, which has spatiotemporal resolutions of 9 km and 50 s, the correlation coefficients of the studied events in August and November were 0.74 and 0.51, respectively, at the point and daily scales, and the mean Heidke skill scores for the two studied events both reached 0.31 at the grid and hourly scales. This study can provide references for the assimilation of TRMM 3B42 or GPM IMERG into the WRF model using 4D-Var, which is especially valuable for hydrological applications of GPM IMERG during the transition period from the TRMM era into the GPM era.

Highlights

Precipitation is a basic and vital component of the global water and energy cycles [1]
CTL experiments were performed based on the Weather Research and Forecasting (WRF) model with different forcing data and for d6.ifCfeornencltuesvioentss
The assessment of the simulated precipitation in the CTL experiments found that wrrimneehppdeteerrhneepTosseodeepnnnrdtrtteoeeeeddddnaisutc,sctcnicioenmoongnnivdl-saehacectotecetanuaitvvvthaieyevecceqprtr,ueiravameiiennscioidftpatpieohilrtllniayegetchsividoep-einrnifnetfi.satsecsMotduiloouolpntvtryri,eeeoorcnfoviotpupehrtirretp,eapecttHrrihieopfReocniitBrpsapm,itimrtiteooahdudnteiluoadtcWnthatestedRaion,FpfpwtehrpheeryefecudroiTfpsrromeoRirtdlmaMoatangiaMoci4ncneDca3el-BgfVo4efsanor2trureadedrneavaidveteteeasnGdntaaPtsbnMAsNydim,IfMooiwwlbraEhhcttiRiaiinocciGhhnng into the atmospheric WRF model

Summary

Introduction

Precipitation is a basic and vital component of the global water and energy cycles [1]. As remote sensing techniques developed, various satellite precipitation products based on visible, infrared, and microwave wavelengths have emerged during the last few decades, such as the Global Precipitation Climatology Project (GPCP) [14], the Climate Prediction Center Morphing technique (CMORPH) [15], the Tropical Rainfall Measuring Mission (TRMM) [16], and its ongoing replacement Global Precipitation Measurement project (GPM) [17]. These products cover a nearly global area, they are available to the public free of charge. Used RCMs include the National Meteorological Center (NMC) forecast model [25,26,27], the next-generation Weather Research and Forecasting (WRF) model [28], the operational Japan Meteorological Agency (JMA) mesoscale model [29], and the European Center for Medium-Range Weather Forecasts (ECMWF) model [30]

Methods

Results

Conclusion