山西北部初终霜冻日特征及其对农业的影响

基于山西北部12个气象站1970～2008年逐日最低气温资料，采用现代气候统计诊断方法计算分析了山西北部霜冻初终日的气候特征，在此基础上，分析了霜冻发生对农业的影响。得出以下主要结论：(1)山西北部霜冻的发生与海拔高度密切相关，海拔越高初霜冻日到来越早、终霜冻日结束越晚；海拔高度对终日的影响>对初日的影响。(2)在山西北部大部分区域，初霜冻日呈现推后的趋势、终霜冻日呈现提前的趋势，但年际间变化大，前后两年相差可达30天以上。(3)山西北部初霜冻日的推后主要是从21世纪开始的；终霜冻日的年代际变化不完全同步，大多数代表站以20世纪90年代为转折点，70和80年代相对偏晚、之后相对偏早。(4)山西北部初霜冻日呈现逐渐推后的变化趋势、终霜冻日呈现逐渐提前的变化趋势使该地春玉米幼苗、成熟后期遭受霜冻危害的可能性大大降低，为当地春玉米提供了有利的生长条件。

Features of First and Last Frost Event Occurrence and Its Influence on Agriculture over Northern Shanxi

Based on the daily minimum temperature data measured at 12 meteorological stations over northern Shanxi from 1970 to 2008, the method of modern climatic diagnosis was used to analyze the climatic features of the first and last frost event occurrence and their influence on agriculture. Here are the results: (1) The relation was obvious both dates of first and last frost event occurrence and altitude, the higher the altitude, the earlier the first frost while it was opposite for the last frost.The influence of altitude on the last frost is more evident than on the first frost.(2) Much of the northern Shanxi,the trend was found that the first frost event occurrence was late while the last frost was seen early,but the anomaly between years was remarkable and it can be over 30d.(3) The delaying trend of the first frost mainly began from 21st century, but the decadal change of the last frost was not synchronous, the turning point appeared in 1990s for most representative stations, it was late in 1970s and 1980s,early in 1990s and 21st century. (4) Along with the change of frost event occurrence, the possibility might be drop markedly for early and late stage of maize growth to suffer from frost, it was advantageous for local maize growth.