Study On Occurrence Regularity And Regional Features Of The Frost In Shanxi Province

Frost as an agrometeorological disaster is always an important project highlighted by meteorological science, agricultural science and other related sciences. The abnormal advancing of the first frost and the obvious delaying of the last frost usually harms crops severely. Based on each year’s first&last frost data of62meteorological stations in Shanxi Province from1961to2010and using mean distribution, probability theory, statistical test, M-K mutation test, EOF analysis, wavelet analysis methods. Variation laws, climatic features and regional features of the first frost, last frost and frost-free period of Shanxi Province are studied in this paper. The spatial distribution, inter-annual variation, inter-decadal variation and cycle characteristics of different intensity frosts are also studied. The main research results are as follows:1The average first frost date of Shanxi province in latest50years has a delaying trend, and the average last frost date of Shanxi province in latest50years has a trend of advance, so the average frost-free period becomes longer. The average first frost date of Shanxi province in latest50years has an obvious inter-decadal variation characteristic just like the letter "W", it was advanced in1970s&1990s, and was delayed in1960s,1980s and this century. The average last frost date of Shanxi province in latest50years has an asymmetric "W" distribution, it was slightly advanced in1960s&1970s, and was delayed in1980s, from1980s to2005it was obviously advanced, after2005it was significantly delayed.2The average first frost date of Shanxi province in latest50years is October7. The first frost appears from the second ten days of September in the north to the first ten days of November in the south with5steps, and it is earlier in the east than the west. The average last frost date of Shanxi province in latest50years is April12. The last frost emerges from the second ten days of March in the south to the second ten days of May in the north.3Probability of the earlier first frost and the earliest first frost in Shanxi Province is respectively6%～26%and4%～22%, the area where there is the biggest probability is located in the middle and the west. Probability of the later last frost and the latest last frost in Shanxi Province is respectively2%～22%and14%-36%, the area where there is the biggest probability is located in the southeast and the northwest.4The main cycles of the mild first frost, the moderate first frost and the severe first frost are2a,3a and6a. The secondary cycles of the mild first frost, the moderate first frost and the severe first frost are10a,5a and9a. The main cycles of the mild last frost, the moderate last frost and the severe last frost are15a,12a and7a. The secondary cycles of the mild last frost, the moderate last frost and the severe last frost are9a,5a and5a.5The occurrence time of the mild first frost, the moderate first frost and the severe first frost shows the same "delay" or "advance" in most years.6The occurrence time of the mild last frost, the moderate last frost and the severe last frost also shows the same "delay" or "advance" in most years.7REOF characteristics analysis show that the mild first (last) frost date, the moderate first(last) frost date, the severe first(last) frost date can be respectively divided into5,5,3relatively independent abnormal types, which reflects the climatic and regional features of Shanxi Province associating with large-scale circulation, topography, cold air intensity and path.