| The Loess Plateau(LP)is a sensitive region of climate change with fragile ecological environment,and global climate change has a significant effect on the ecological and economic environment of the LP.Therefore,it is of great practical significance to systematically analyze the spatiotemporal change trends of climate over the history and future period,and to develop flexible adaptation and mitigation strategies against the global climate change issues for this region.This study takes the LP as the research area,using the Delta method to downscale the CRU and GCMs monthly climate datasets published by CMIP5.The downscaled datasets were evaluated and screened based on meteorological observation data from 113 meteorological stations inside and outside the research area in order to obtain temperature and precipitation datasets with high spatial resolution(approximately 1 km)in the history and future periods of the LP.Afterwards,the spatiotemporal changes and trends of annual and seasonal climate of the LP from 1901-2100,as well as from 2071-2100,are analyzed by using the methods of anomalies,Mann-Kendall trend test,and Sen's slope estimation.This research provides a theoretical basis and scientific guidance for the LP in formulating strategies for responding to global climate change.The main results are as following:(1)The Delta downscaling method performs well in downscaling the meteorological data of 0.5 ° grid resolution to a grid with 1 km spatial resolution,where the monthly mean temperature downscaling result is better than the monthly precipitation downscaling result.Among the four interpolation methods,the bilinear interpolation is the best method for the downscaling process.The most suitable climate models to reflect monthly mean temperature and monthly precipitation in the future of the LP are the NorESM1-M model and GFDL-ESM2 M model,respectively.(2)During 1901-2014,the annual mean temperature presents a significantly increasing trend with 0.1 ?/10 year,while the annual precipitation has no significant trend.Compared with the average of the climate during 1961-1990,the climate in 1960 s is cold and wet,while after 1980 s it is dry and warm.The annual mean temperature in the zone apart from the west of the LP region(accounting for 91.30 % area)show a significantly increasing trend,ranging from 0.02 to 0.17 ?/10 year during 1901-2014,and these trend magnitudes increase from southwest to northeast.The annual precipitation in the west of the LP region(accounting for 3.05 % area)shows a significantly increasing trend,ranging from 0.24 to 3.52 mm/10 year during 1901-2014.(3)During 1901-2014,mean temperature of the LP have no significant trend.However,in the summer,and the other mean temperature of seasons present a significantly increasing trend.The precipitation in the four seasons has no significant trend.The mean temperature of the four seasons during 1901-1919 is low,and enters the 21 st century warm generally.The precipitation of the four seasons doesn't show an obvious increase or decrease trend.The trend of mean temperature and precipitation in the four seasons is very different in spatial distribution.The average increase of winter warming in the four seasons is the largest,and the average rate of precipitation decrease is the smallest.(4)During 2015-2100,the annual mean temperature of the LP will present a significantly increasing trend under the three kinds of RCP scenarios,while the annual precipitation will has no significant trend.Under the three kinds of RCP scenarios,the annual mean temperature and annual precipitation will growing compared with the climate average in the early,middle and end of the 21 st century.The changes of annual mean temperature and annual precipitation will be the largest under the RCP8.5 scenario.The areas where the annual mean temperature will has a significant trend under the three RCP scenarios show an upward trend.The annual precipitation will only in the area where there is no significant trend under the RCP2.6 scenario,and the areas with significant trend will increasing trend under the other two scenarios.The trend of annual mean temperature and annual precipitation will be very different in spatial distribution.(5)During 2015-2100,mean temperature of the LP will has no significant trend only in the spring and autumn under the RCP2.6 scenario,and the other mean temperature of seasons will present a significantly increasing trend.Under the same RCP scenario,the winter average rate of temperature increases faster.The precipitation will show a significantly increasing trend only in the spring under the RCP4.5 and RCP8.5 scenarios,and the other precipitation of seasons will have no significant trend.Under the three kinds of RCP scenarios,the mean temperature of the four seasons will growing compared with the climate average in the early,middle and end of the 21 st century,while the precipitation increases only in the spring.The changes of mean temperature and precipitation in winter will be the largest under the RCP8.5 scenario.The trend of mean temperature and precipitation in the four seasons will be very different in spatial distribution under the three kinds of RCP scenarios.Under the RCP8.5 scenario,the average rate of warming in winter will be the largest in the four seasons,and under the same RCP scenario,the growing rate of summer precipitation will be the largest and the winter increase rate will be small.(6)During 2071-2100,the annual mean temperature and seasonal mean temperature for the entire LP all will have warmed up under the three RCP scenarios.The annual precipitation will increase during the almost the entire LP only under the RCP4.5 and RCP8.5 scenarios.Under the RCP2.6 scenario,the annual precipitation will increase in the zone outside of Shaanxi,Shanxi and Baotou(accounting for 79.74 % area).The change of precipitation in the four seasons will be very different in spatial distribution.Under the three RCP scenarios,the mean temperature and precipitation of the four seasons all will increase the most under the RCP8.5 scenario.Under the same RCP scenario,the grow rate of precipitation in the spring and winter will be the largest,and the area of the increase is also the largest.Compared with the historical period,Linhe,Huinong and Taole all will produce precipitation in the winter of the late 21 st century. |
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