基于最优拟合函数的SPI指数的松嫩平原干旱特征分析

松嫩平原是我国重要的商品粮生产基地，利用松嫩平原21个气象站点1961—2015年逐月降水数据，选用基于最优拟合函数的标准化降水指数作为干旱指标，分别从干旱频率、干旱历时、干旱站次比等角度，分析松嫩平原干旱的时空变化特征. 从季节来看，松嫩平原冬季出现了显著的湿润趋势（P=0.002），春季次之(P=0.039)，两季的干旱频率分别为26%和29.7%，且均有重旱现象发生；夏季和秋季呈干旱化趋势，干旱频率均为22.2%，但没有重旱现象发生.从年尺度上看，松嫩平原54 a间发生持续时间为7个月及以上的干旱事件共7次，远高于其他连旱事件的次数，但总体表现为湿润化趋势. 从空间来看，在年、季尺度上干旱频率整体从西南向东北递增，冬季的高频干旱区主要分布于泰来、明水和扶余及其周边地区，呈零星分布；春季和夏季主要集中于松嫩平原东北部，其中春季的高频干旱区面积大于夏季的高频干旱区面积；秋季主要集中于松嫩平原西北部和中部，主要分布于富裕、齐齐哈尔和安达等地.尽管松嫩平原的干旱严重程度有所下降，但54 a间有39次出现了全域性干旱，并且干旱的影响区域呈扩大趋势.该结论能为松嫩平原的抗旱减灾及保障粮食安全提供一定的科学理论指导. 

Drought characteristics in Songnen Plain with SPI calculated by optimal probability function

Songnen Plain is an important region for grain production. Precipitation data from 21 weather stations in Songnen Plain from 1961 to 2015 were examined, standardized precipitation index by optimal fitting was used to construct drought index. Spatial-temporal drought characteristics were analyzed for drought frequency, duration and occurring-station ratios. Songnen Plain was found to show a significant wetting tendency in winter ( P = 0.002) and spring ( P = 0.039), with corresponding drought frequency of 26% and 29.7% respectively, indicating a heavy drought. Whilst arid tendency and drought frequency of 22.2% was found in summer and autumn, no heavy drought was indicated. Although a total of 7 drought events lasting more than 7 months in 54 a were found on an annual scale, much higher than duration of other drought events, a wetting trend was indicated. Drought frequency was found to increase from southwest to northeast on annual and seasonal scales. High-frequency arid regions in winter were mainly found distributed in Tailai, Mingshui and Fuyu and surrounding areas, showing a sporadic distribution pattern. High-frequency arid regions in spring and summer were mainly found concentrated in northeastern part of Songnen Plain. High-frequency arid area in spring was found to be larger than high-frequency arid area in summer. In autumn it was found mainly concentrated in northwest and central part of Songnen Plain, mainly distributed in Fuyu, Qiqihar and Anda. Although drought severity of Songnen Plain has declined, station proportion of drought was found to be greater than 50% and area affected by drought has expanded. This work will provide some guidance for drought and mitigation, and for protection of food security in Songnen Plain.