The Impact of Global Warming on Frost-Free Periods from 1961 to 2010 in Xinjiang

Based on daily temperature data from 1961 to 2010 from 101 meteorological stations in Xinjiang,the spatial-temporal change characteristic of annual mean temperature,first and late frost dates,and frost-free period were analyzed using linear regression,accumulative anomaly,T-tests and mixed spatial interpolation methods.We found that the spatial distribution of first and late frost dates and frost-free periods closely corresponded to annual mean temperature.For example,when the annual mean temperature is higher,the late frost date is earlier,first frost date is later and frost-free period is longer.Under a context of global warming,annual mean temperature rose 0.33° C/10 a and the late frost date advanced by-1.41 d/10 a,the first frost date was delayed by 2.21 d/10 a,and the frost-free period increased by 3.59 d/10 a.These changes experienced significant mutation in 1997 or 1995 whereby the rate of change before and after these dates was different in different areas.Generally,the advance rate or range of late frost dates,the delayed rate or range of first frost dates,and the increasing rate or range of frost-free periods were greater in areas that underwent a greater increase in annual mean temperature.