Variation Of Extreme Temperature In Gansu And Its Sensitivity Analysis To WRF Model With Different Land Surface Schemes

Based on the daily extreme temperature (ET) data observed by81stations in GanSu Province from1982to2011, the spatio-temporal evolution characteristics of extreme air temperature were analyzed. The moving cut data-approximate entropy(MC-ApEn) and the moving t test to be used to detect the climate abrupt change of the high-ET in summer and low-ET in winter, as well as discussing the probable reasons of it. At the same time three land surface schemes(SLAB,NOAH and RUC)in WRF model are used to simulate2m temperature of the Southeast and Northwest in Gansu.The results shows that:(1)The first EOF eigenvector of the frequency of the high-ET in summer and winter shows the consistent change all over Qansu, and over70%of total variance is explained. The time coefficient indicates that the frequency of extreme maximum temperature increases obviously;The first EOF eigenvector of the frequency of low-ET in winter explains59.3%of total variance, which also shows consistent change.The time coefficient indicates that the extreme minimum temperature frequency increases. The high-ET in summer have climate abrupt change and it occurred at the end of1980s.At the same time We can proved the change of zonal index is the primary cause of abrupt change in high-ET.(2)The simulated2m temperature generally is sensitive to different land surface schemes and agree with the scope and the number of observations in different regions.Generally, three schemes are more reasonable in simulating the High-ET than simulating he Low-ET,and more reasonable in Southeast of Gansu.SLAB scheme is better than the other land surface scheme in the Southeast, NOAH scheme presents best in northwest of Gansu,and there are no more different in simulating the high-ET at daytime and the low-ET at nighttime.(3)The reasons of the model performance difference with difference Land surface scheme is the prediction of meteorological variables--surface skin temperature, upward heat flux and latent heat flue at the surface.The distributed of surface skin temperature decided the tendency of2m temperature,the value of upward heat flux is a very important factor to decide the temperature.