近50年宁夏霜冻日数基本特征及变化趋势

利用1961—2010年宁夏全区20个气象站的逐日最低气温资料，根据霜冻气候指标统计了霜冻日数。采用现代气候统计诊断方法，研究了近50年来宁夏全区及不同区域霜冻日数基本特征和变化趋势。结果表明：近50年宁夏平均每站每年的霜冻日数为10.4日次，其中春霜冻日数占58%，秋霜冻日数占42%；从区域上看，引黄灌区的霜冻日数最少，中部干旱带次之，南部山区最多；宁夏全区近50年来的年霜冻日数、春霜冻日数和秋霜冻日数均呈现明显减少趋势，3个区域的霜冻日数变化趋势与全区保持一致；年代际变化上，20世纪80年代前宁夏全区的霜冻日数多于近50年平均，而之后的两个时代均少于50年平均，3个区域的霜冻日数年代际变化与全区类似，春霜冻日数及秋霜冻日数的年代际变化与全年霜冻日数的变化规律相似；宁夏的霜冻日数突变发生在1986年，春霜冻日数突变发生在1991年，而秋霜冻突变出现在1974年。受气候变暖影响，宁夏的霜冻日数总体上呈现下降趋势。研究结果可为本区合理制定霜冻灾害防御措施提供依据。

Characteristics and Change Trend of Frost Days in NingXia in Recent 50 Years

Based on the daily minimum temperature data at 20 meteorological stations in NingXia during 1961-2010, the frost days were calculated according to the climatic index on frost. Using climatic diagnosis methods，characteristics and change trend of frost days were studied. The results showed that the average number of frost days was 10.4 times each station every year. The spring frost days accounted for 58%, autumn frost days accounted for 42%. In the three regions，the sort order of the frost days was Yellow River irrigation area＜Middle Dry area＜South Mountain area. In recent 50 years, the total frost days, spring frost days and autumn frost days all showed the decreasing trend. Change trends of three regions were all similar with that of the whole autonomous region. Decadal variation showed that，before the 1980s, frost days were more than the average of 50 years, and after 1980s, frost days were less than the average of 50 years. Three regions’ decadal characteristics of frost days were similar with that of the whole autonomous region. Mutation of total frost days occurred in 1986, mutation of spring frost days occurred in 1991, but of autumn frost days occurred in 1974. In the background of global warming in the last 50 years, the frost days are in decline in NingXia. The study can provide a basis for the meteorological service of frost in Ningxia.