Study On The Spatiotemporal Characteristics Of Surface Wind Speed In The Loess Plateau And Its Surrounding Areas

In this study,the surface wind speed(SWS)in the Loess Plateau and its surrounding regions(LPSR)during 1979-2019 is analyzed.The LPSR is divided into three sub-regions based on station elevation: region 1-Inner Mongolia Plateau(IMP);region 2-Loess Plateau(LP);and region 3-eastern Qinghai-Tibet Plateau(EQTP).Firstly,the daily mean and daily maximum SWS over LPSR are homogenized using the Multiple Analysis of Series for Homogenization(MASH)method.Subsequently,the spatiotemporal characteristics of the SWS in the LPSR after homogenization are analyzed.Finally,the atmospheric circulation patterns affecting the spring SWS of the LPSR are investigated,and the following conclusions are drawn:(1)Statistic results shows the homogenization is acceptable.The differences of SWS climatology between before and after the homogenization is insignificant,while the liner trends changed significantly.The adjustments of daily maximum SWS are larger than that of daily mean SWS.Among the three sub-regions,IMP region has the largest adjustments while the smallest in EQTP.(2)The SWS climatology and trends present significant spatial differences.Larger SWS appear at approximately north of 37.5°N and the four mountain stations in the south.Mean SWS at most stations exhibit downward trends.There are differences between each sub-regions in the daily mean and daily maximum SWS.The daily mean SWS in the IMP and EQTP regions exhibit increasing trends after decreasing trends,with turning points(TPs)in 2005 and 1999,respectively.The TPs occurred in 1989,1995,and 2008 in the LP region,with decreasing,increasing,decreasing,and increasing trend distribution.The daily maximum SWS exhibit decreasing trends in the three sub-regions.For strong wind days,the TP occurred in 1989 in IMP region,and in LP region and EQTP are the same as the daily average SWS's.The seasonal importance of variation in winter and spring are relatively high compare to summer and autumn over LPSR.(3)At the strong SWS year in spring over LPSR,the Ural blocking developed,while the geopotential height near Lake Baikal is lower leading the meridional direction of circulation increased,which is conducive to the downward movement of cold air.Compare to climatology,the spring mean SWS over LPSR is higher under Okhotsk trough,Ural blocking type II and double blocking regime;Higher in the IMP and EQTP regions and lower in LP region under Ural blocking type I regime;Higher in the IMP and central LP regions,lower in the eastern LP and EQTP regions under Central Siberian trough regime;lower in West Siberian trough and Baikal ridge regimes.The interannual variation of spring mean SWS under each weather regime confirms the SWS spatial distribution is reliable.Due to the appearance of the Ural blocking type I and II and the Central Siberian trough regimes,the SWS in spring in 2021 is stronger than climatology.