Frost Spatial and Temporal Variations Analysis in Hengduan Mountains

In this paper,using the climate diagnostic analysis method and surface temperature not more than 0℃ as a indicator of frost,the first frost date,the last frost date and frost-free period variations were analyzed,according to the minimum daily surface temperature data of 27 meteorological stations in Hengduan Mountains during 1961-2007.The results showed that the first frost date postponed by 1.09d/10a climate tendency rate,the last frost date ahead by 4.02d/10a,Frost-free period extended by 4.08d/10a,and there were obvious geographical differences in Hengduan Mountains.In most districts of Hengduan Mountains,the last frost dates' inter-annual differences were more than the first frost dates',but the frost-free periods'inter-annual differences was the most.From the decadal changes,since the 1990s,the date of the first frost in the 1990s significantly delayed,the last frost date significantly ahead,and the frost-free period significantly longer than before.