Climatic Characteristics of the Frost Season Variation During the Last Forty Years in Lhasa

The climatic characteristics and variation of the frostless period and first (late) frost date from 1954 to 1996 in Lhasa were investigated using climatological statistics method. The results show that the absolute variability of the frostless season is more than that of the first and late frost dates. The postponed probability of late frost date is bigger than the one of first frost date. The general trend was shorter for frostless period from 1954 to 1998. After 1989 the frostless period was prolonged.