河西走廊东部冰雹的气候特征及天气特征

利用线性回归分析、Mann-Kendall检验和小波分析法，统计分析河西走廊东部1961-2010年近50 a来冰雹日数的变化规律。结果表明：河西走廊东部冰雹日数时空分布差异较大，从祁连山区到走廊平川区冰雹日数迅速递减；年冰雹日数变化总体呈下降趋势，其线性倾向率为-0.164 3 次•a-¹；一年中冰雹出现时段集中在6-9月，一日集中在12：00-18：00；冰雹持续时间在1～20 min。采用Mann Kendall检验法进行检验，河西走廊东部年冰雹日数从1985年开始减少，突变点出现在2006年，2006年后冰雹日数显著减少。在全球变暖的气候背景下，河西走廊东部冰雹日数呈减少趋势，但开始减少和显著减少的时间均滞后于年平均气温开始上升和显著上升时间。小波分析结果表明，河西走廊东部冰雹日数存在9 a的准周期变化。根据冰雹天气发生的物理机制和高低空环流配置，将冰雹出现的大尺度高空环流形势归纳为西北气流型、西风气流型、低压槽型3大类。对每种大尺度高空环流形势下700 hPa中尺度环流进一步细化，分析了每种冰雹类型的垂直环流特征及影响程度。

Analysis on Hail and Weather Characteristics in the East Hexi Corridor,Gansu Province

In this paper, the linear regression analysis, Mann-Kendall test and wavelet analysis were used to analyze the variation of annual hail days in the east Hexi Corridor in China in recent 50 years based on the data of annual hail days from 1961 to 2010. Results show that there was an obvious difference in spatiotemporal distribution of annual hail days in the corridor. Spatially, the annual hail days decreased apparently from the Qilian Mountains to the corridor plain, and temporally, there was a decrease trend in overall change of annual hail days with a linear decrease rate of -0.164 3 times•a^-1. Hail occurred generally at 12:00-18:00 o’clock during the period from June to September, and its duration varied in a range of 1-20 minutes. The Mann-Kendall test was used to test the change of annual hail days in the east Hexi Corridor, the results revealed that the annual hail days started to decrease from 1985, an abrupt change occurred in 2006, and after that a significant reduction occurred. Under global climate warming, the annual hail days in the east Hexi Corridor were in a decrease trend, but such trend was delayed than the time when temperature was increased. Wavelet analysis showed that there was a 9-year quasi periodic change in annual hail days in the east Hexi Corridor. According to the physical mechanism of occurring hail and upper and low air circulation, the large scale upper air circulation when hail weather occurred could be divided into the northwest airflow type, westerly airflow type and low pressure through type. On which the mesoscale air circulation at 700 hPa could be further divided, and each hail type of vertical circulation and its affecting extent were analyzed.