山西近50a初霜冻的气候变化特征及其周期分析

初霜冻13的变化对农业生产的布局和耕作模式具有一定的影响。利用山西62个气象观测站点1961－2010年的逐年初霜冻日及逐日最低地温资料，应用统计学方法分析了山西初霜冻日的变化特征，结果表明：1）山西近50a平均初霜冻日的时间分布总体为推后趋势，且具有明显的年代际特征，20世纪70年代、90年代初霜冻日提早显著，20世纪60年代、80年代和21世纪初霜冻日明显推后。2）山西近50a平均初霜冻日的空间分布为“5级阶梯”型分布，从9月中旬到11月上旬，自北向南相继出现初霜冻。3）M—K突变检验表明，山西近50a平均初霜冻日在1989年发生了一次显著的气候突变。4）山西近50a初霜冻日变化趋势的分布具有明显的区域特征，大部分地区初霜冻日有推后的趋势，但南部和中南部的部分地区初霜冻日有提前的趋势。5）Morlet小波分析结果表明，山西的初霜冻、轻微初霜冻、中度初霜冻和重度初霜冻发生的主周期分别为5a、2a、5a、6a；目前山西正处在初霜冻和轻微初霜冻的推后期、中度初霜冻和重度初霜冻的提前期。

Analysis of the climate change characteristics and periodicity of the first frost in Shanxi Province in the past 5 decades

Change of the first frost date has obvious effect on agricultural distribution and farming pat tern. Based on each year＇s first frost date data and each day＇s minimum ground temperature data from 62 meteorological stations in Shanxi Province from 1961 to 2010, the first frost date climate change characteristics and its periodicity in Shanxi Province are analyzed with statistical method. The results show that： 1 ） The average first frost date in Shanxi Province has a delaying trend and changes with dec ades. It was advanced visibly in the seventies and the nineties of the twentieth century and was delayed obviously in the sixties and the eighties of the twentieth century and in this century. 2） The spatial dis tribution of the first frost dates in Shanxi Province appears from the north to the south in five steps;it appears from the second ten days of September in the north to the first ten days of November in the south. 3 ） The average first frost date in Shanxi Province had a mutation in 1989.4） The first frost date in most areas has a delaying trend, with exception only in some areas such as the south and middle south parts. 5） The Morlet analysis results show that cycles of the first frost frequency, the mild first frost frequency ,the moderate first frost frequency and the severe first frost frequency are 5 a,2 a,5 a,6 a respectively. Now, Shanxi is in the phase when the first frost and the mild first frosts are delayingwhile the moderate and severe first frosts are advancing.