青藏高原东北边坡冰雹天气的时空变化分析

Spatiotemporal Variation of Hail Weather in the Northeast Qinghai- Tibetan Plateau

利用1961—2010年青藏高原东北边坡地区60个台站的冰雹资料,研究青藏高原东北边坡地区冰雹的时空分布及冰雹的年代际演变规律。研究表明:①一般情况下,冰雹出现在每年的4—11月,6月出现频率最高;日变化主要集中在12:00—20:00(北京时间,下同),其中14:00—18:00最盛,并且不同月、不同年代际的日变化存在较明显的差异,而不同月的峰值时间可以作为冰雹预报的一个参考指标。②冰雹的地理分布从西南向东北递减,西北和东南分布较少,中部地区较多,并且冰雹次数与海拔高度呈显著正相关。③从年代际距平空间分布来看,20世纪80年代高原边缘地区的冰雹次数达到峰值,但近十几年却显著减少,这一特征与气温变化趋势较为一致,表明它们之间的相关性。④从年际变化来看,从20世纪60年代开始持续增加,90年代开始又呈现持续减少的趋势,特别是近10 a来减少趋势明显增强。

Based on the data from 60 stations in the northeast Qinghai -Tibetan Plateau during the period of 1961 -2010, the spatiotemporal and decadal variations of hail weather were analyzed statistically. The results are as follows： （1） Hail disasters occurred generally from April to November, but the maximum frequency occurred in June. The daily variation of hail weather centralized from 12：00 to 20：00 （ Beijing time）, especially from 14：00 to 18：00, it was quite different from different months and decades, and the peak-value time could be regarded as a reference indicator in forecasting hail weather; （2） Geographically, hail weather decreased from the southwest to the northeast, more in central region, and less in the northwest and the southeast, and there was a significant positive correlation between hail frequency and altitude; （3） The occurring frequency of hail weather was the highest in the 1980s, and it was sharply decreased in recent dozen years. Such change trend revealed that there was a correlation between the changes of hail weather and temperature; （4） Viewing from the decadal variation, the occurring frequency of hail weather was continuously increased in the 1960s, but continuously decreased in the 1990s, especially in recent dozen years.