摘要:呼伦贝尔草原是我国北方地区重要的防风固沙和水源涵养生态功能区，在气候变化的背景下，该区的草原畜牧业和旱作农业深受干旱的影响。研究该区干旱发生的特征及趋势，对当地采取适应气候变化对策具有重要意义。基于1960-2017年呼伦贝尔草原4个气象站逐月降水和气温资料，计算标准化降水蒸散指数（SPEI），并采用Mann-Kendall突变检验、Morlet小波分析和R/S分析法分析了近58年呼伦贝尔草原年、季尺度的气候变化及干旱特征与趋势，并结合该区实际发生的灾害事件对SPEI指数进行了验证。结果表明：1）近58年来呼伦贝尔草原在气温显著上升，降水量减少的背景下干旱化趋势显著。2）该区域年尺度和季节尺度下干旱化特征具有差异性，其中，年尺度下，该区域SPEI指数以-0.218×10 a^-1倾向率呈显著下降趋势，1998年是干旱加剧的突变年，未来在11年尺度上有持续偏旱的趋势；季节尺度下，冬季SPEI指数显著增加，且未来在17年尺度上有持续偏湿的趋势，春、夏和秋季的SPEI指数均呈下降趋势，并分别在22年、9年和15年尺度上有持续偏旱的趋势。3）2000年以来，干旱发生的总频率尤其重旱和极旱的发生频率均显著高于其他年代；4）夏季和秋季分别是发生重旱和极旱次数最多的季节。5） SPEI指数在呼伦贝尔草原区的干旱监测与分析中具有较好的适用性。



Abstract:With increases in global warming intensity, the frequency and duration of droughts are showing a clear upward trend, and the global terrestrial extreme drought area is expanding, particularly on the Eurasian and African continents. Hulun Buir grassland is an important wind-fixing and water-reserving ecological functioning area in northern China. However, due to the superimposition of climate change effects, such as the frequency of drought, and human activities, the grasslands have gradually degraded to a simpler community structure with reduced species diversity, intensified desertification, and increased pests and diseases. Based on monthly precipitation and temperature data from four meteorological stations in the Hulun Buir grassland from 1960 to 2017, the standardized precipitation evapotranspiration index (SPEI) was calculated. The Mann-Kendall mutation test, Morlet wavelet analysis, and R/S analysis were used to analyze the drought change characteristics and trends on both annual and seasonal scales in the Hulun Buir grassland over the past 58 years, and the SPEI index was verified by the actual disaster events in the area. The results show that:1) between 1960 and 2017, the temperature of the Hulun Buir grassland increased gradually at a significance level of 0.05, while precipitation showed a slight decrease. In addition, the seasonal variations in temperature and precipitation are different. Among them, summer precipitation is gradually decreasing, while the other seasons are increasing at different rates. In addition to winter temperatures, the interannual temperature changes in other seasons showed an upward trend at a significance level of 0.05. Among them, the spring temperature rose at the fastest rate, reaching 0.46℃×10 a^-1, followed by summer (0.39℃×10 a^-1). 2) On the annual scale, the SPEI index of this region showed a downward trend with a tendency of -0.218×10a^-1 (P < 0.01). 1998 is the year of drought intensified in the region, and there is a trend of persistent drought on the 11 a scale for the future; On the seasonal scale, the winter SPEI index increased significantly, and there is a trend of continuous wetness on the 17 a scale for the future. However, the SPEI index in spring, summer, and autumn showed a downward trend, and there was a trend of persistent drought on the 22 a, 9 a and 15 a scales, respectively; 3) The frequency of moderate drought occurrences is the highest among different years and seasons, and that of extreme drought is the lowest. At the beginning of the 21st century, the frequency of drought, especially severe drought and extreme drought, was significantly higher than for the past four decades. 4) Summer and autumn were the seasons with the most frequent occurrences of severe and extreme droughts, respectively. 5) The SPEI index can well characterize the drought characteristics of the Hulun Buir grassland.





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