Study On Potential Evapotranspiration And Drought Response In Poyang Lake Basin In Future Scenarios

Climate change has become the focus of the international community,which has a profound impact on the survival and development of human society.Potential evapotranspiration(ET0)as an important physical quantity connected meteorological elements and water circulation,which is an important indicator to evaluate region water resources and calculate crop potential production.In this study,the Poyang Lake Basin in China was used as a research area.We used 11 global climate model output data from the fifth phase of the Global Climate Coupling Model Comparison Program(CMIP5),and the reanalyzed data from the US Environmental Center and daily observation data from river basin meteorological stations.Relying on the statistical downscaling model(SDSM)the genetic algorithm was used to calculate the optimal weight coefficient of each climate model to build a multi-model ensemble.We focused on the temporal and spatial evolution characteristics and periodic changes of potential evapotranspiration and Drought Index(DI)in the Poyang Lake Basin under the RCP4.5 and RCP8.5 scenarios.It can provide in-depth understanding of the watershed water cycle and water balance laws and accurately understand the impact of future climate change on the potential evapotranspiration of the watershed,which can provide the decision support for relevant departments to scientifically respond to changes of the future drought situation in the Poyang Lake Basin.The main conclusions are as follows:(1)From 1961 to 2014,the average annual ET0 of the Poyang Lake Basin showed a general downward trend,and in the seasonal distribution the ET0 of the watershed showed a high summer and low winter.The spatial distribution of ET0 is high in the north and south and low in the middle with obvious spatial differences.The decrease of sunshine hours is the main factor that causes the decrease of ET0 in the Poyang Lake Basin,while the increase of temperature has relatively little effect on ET0.(2)The simulation accuracy of the downscaling model after deviation correction has been significantly improved,which showed a good applicability in the Poyang Lake watershed.The multi-mode ensemble based on genetic algorithm has smaller centralized root-mean-square error and higher correlation coefficient.The performance ranking of CMIP5 mode is GA-MME>MME>single mode.The results is the multi-mode ensemble based on genetic algorithm compared with any single climate model and equal weight model collection,Which has better simulation performance.(3)Under the RCP4.5 and RCP8.5 scenarios,the annual average ET0 of the Poyang Lake Basin will rise in the future period(2011-2100),and the annual change trend was showed sa an inverted "U" In the RCP4.5 scenario,the basin's ET0 is the first main cycle of change on the 20-year scale,and in the RCP8.5 scenario,the ET0 is the first main cycle of change on the 4-year scale.Under the two scenarios,the spatial variation characteristics of ET0 in the basin in the next three periods are relatively similar,which basically showing high in the east and low in the west with a slightly prominent local distribution.(4)During the historical period(1961-2010),the DI value of the Poyang Lake Basin showed a fluctuated increase.The seasonal distribution of DI was high in summer and autumn,low in spring and winter.The spatial distribution was high in the south and southeast of the basin,and low in the north.Under the RCP8.5 scenario,the annual average DI in the watershed showed a significant upward trend(P<0.01).The highest DI value in autumn which is the key period for preventing drought risk in the watershed.8 years was the first main cycle of the annual DI evolution in the watershed.Under the RCP8.5 scenario,the Poyang Lake Basin will eventually form a spatial distribution pattern with the middle and eastern parts of the basin as the high value area of DI.Which means that the northeast of the Ganjiang Sub Basin and the south of the Fuhe Sub Basin will be the key area of future drought risk prevention in the Poyang Lake Basin region.