Research On The Applicability Of Satellite Precipitation Products Based On VIC Model In Ganjiang Basin

Precipitation is one of the important meteorological elements.It has a direct impact on ecological and hydrological cycles,and more directly affects people's daily lives.Therefore,it is practically important to capture precipitation over regions.It is known that,the quality of the precipitation data directly affect the results of the hydrological simulation.Traditional precipitation measurement instrument like rain gauge cannot meet the requirements of acquisition of quantitative precipitation estimation(QPE)product over large-scale regions especially complex terrain.With the rapid development of remote sensing technology to measure precipitation,it is feasible to obtain large-scale QPE products with wide coverage in high spatiotemporal resolution.High resolution QPE products are widely used in hydrological research in a large area.At present,the most widely used remote sensing precipitation product is the TRMM Multi-satellite Precipitation Analysis(TMPA)products derived from the observations of TRMM satellite launched in 1997.Since the release of the TMPA,the algorithm has been continuously improved to increase the accuracy of precipitation estimation.Such kind of good QPE product facilitates the research of hydrological simulation and flood forecast.However,TRMM has been retired in 2015 due to the end of fuel.The successor Global Precipitation Measurement(GPM)mission was launched on 27 February 2014 with the aim to develop better QPE product with quasi-global coverage based on the TMPA algorithm.Up to date,the latest satellite QPE products are the Integrated Multi-satellite Retrievals for GPM(IMERG)with version 06B(V06B).However,to the best of our knowledge,little effort has been reported in evaluating and quantifying the reliability,accuracy,and utility of the latest V06 IMERG over China and other regions around the world.The Ganjiang River is the largest river in Jiangxi Province.It flows from north to south and passes through the entire north-south border of Jiangxi.The Ganjiang Basin has a rich topography and landform pattern.The droughts and floodings are more and more frequent in the Ganjiang basin that commands more and more attention.Therefore,studies on water resources in the Ganjiang basin are of great importance.This thesis mainly primarily focused on the evaluation of performance of GPM/IMERG Final and Early products in the Ganjiang Basin and its potential hydrological utility based on simulation with the VIC hydrological model.Taking the observational rainfall data and runoff data from the ground stations as the reference data,the satellite QPE products V06 B IMERG and TRMM V7 TMPA are firstly used for precipitation estimation research,and then used to drive the VIC hydrological model for hydrological simulation in the Ganjiang Basin.The accuracy of runoff simulation,and the applicability of IMERG and TMPA in Ganjiang basin are then evaluated.The conclusions are as follows:(1)In terms of daily precipitation,it is found that among the three products of Final,Early,and TMPA,Final has the best performance and the highest degree of agreement with the standard data,and the degree of deviation is all Less than 10%.Early has a poor ability to capture the spatial distribution characteristics of precipitation in the study area,and the daily precipitation has a large deviation from the reference data,and the quality is not as good as Final.(2)Either on daily scale or monthly,Final has the best estimation accuracy,while Early in the precipitation accuracy estimation is slightly inferior.But it is worth noting that the accuracy of TMPA is similar to Final in many cases.(3)Hydrology simulation with the distributed hydrological model VIC shows that IMERG and TMPA haves promising applicability in the Ganjiang Basin.Final has the best simulation effect in the study area.The deviation of the runoff simulation from the reference data is about1.10%,and the correlation coefficient was as high as 0.85.The Nash coefficient reached 0.7,which is close to the runoff simulation result of the measured precipitation.Additionally,although the test coefficients of the TRMM and Early product simulation results are worse than Final,they can still basically reflect the runoff trend of the hydrological stations in the study area.(4)Using Probability of Detection(POD),False Alarm Ratio(FAR),Critical Success Index(CSI),Correlation Coefficient(CC),Relative Bias(RB),and Root Mean Square Error(RMSE)to evaluate the runoff simulation results of the precipitation data of the three satellite products with different thresholds,it is found that the IMERG and TMPA products show close performances,with Final being the best and TRMM second.Through direct comparison with gauge observations and runoff simulation with VIC model,the results show that Final has a promising application ability in the Ganjiang Basin.Both IMERG Final and TMPA products can generally capture the daily and monthly precipitation in the Ganjiang Basin,but they still have large errors in the simulation of hydrological processes.This shows that further improvement is still needed for IMERG algorithm to obtain more accurate QPE products.