1961—2007年我国霜冻变化特征

利用1961—2007年我国577个测站的均一化逐日最低气温资料, 根据通用的霜冻气候统计指标计算历年初、终霜冻日期及无霜冻期。结果显示:初、终霜冻日期及无霜冻期标准差和极差北方地区较南方地区偏小; 全国大部地区终霜冻日期的年际间差异比初霜冻日期大, 无霜冻期的年际变化又比终霜冻日期大; 从线性变化趋势看, 近47年, 全国平均终霜冻日期提早2.0d/10a, 初霜冻日期推迟1.3d/10a, 无霜冻期延长3.4d/10a;终霜冻日期提早幅度大于初霜冻日期推迟幅度; 从年代际变化来看, 全国平均终霜冻日期自20世纪80年代起明显提早, 初霜冻日期20世纪90年代开始明显推迟, 全国平均终霜冻日期提早时间明显比初霜冻日期推迟时间长; 同终霜冻期年代际变化一样, 全国平均无霜冻期自20世纪80年代起明显延长。

Characteristics of Frost Changes from 1961 to 2007 over China

Based on the daily minimum temperature data at 577 meteorological stations over China from 1961 to 2007, the first frost date, the last frost date and the frost free days are calculated by using the common climatic index on frost day. The results show that the standard deviation of the first frost date, the last frost date and the frost free days is less in the north than in the south of China, which indicates that they are more stabile in the north than in the south. The inter annual variation of the last frost date is larger than those of the first frost date, and the inter annual variation of the frost free days is larger than those of the last frost date in most areas of China. It can be seen from the linear change trend that the last frost date is 2.0 d/10a ahead of time, the first frost date has 1.3 d/10a delay and the frost free days prolong 3.4 d/10a over the past 47 years. From the climate trend it can be found that the range of the ahead last frost date is more than that of the delayed first frost date, which implies that the main cause of the prolonged frost free days is the ahead of last frost day. The first frost date obviously delays since 1990s. The last frost date is obviously ahead of time and the frost free days obviously prolong since 1980s. The ahead of last frost date is earlier than the first frost date delay in China from the inter annual variation.