华北不同地表覆盖类型区干旱演变特征

Drought evolution of different land cover regions in North China

利用华北地区气象站点1960～2008年共49年的降水旬数据集逐旬计算1个月、3个月、12个月尺度的标准化降水指数(SPI)序列。采用SPI历史序列的多年滑动平均和滑动标准差方法,解析研究区及3种主要地表覆盖类型区(草原区、农田区、阔叶林带)干旱在整个时间序列上的演变周期和幅度。采用线性回归分析干旱的演变趋势和变化频度,并对趋势线进行预测。对比了3个子区域全年12个月份干旱演变特征的差异。结果表明:研究区干旱发生的频率和强度呈逐渐加重的趋势,且各月份干旱发展趋势有较大差异,夏季的6月、7月降水较历史时期增多,春旱(4月)、秋旱(9月和10月)加重趋势显著。草原区在整个历史时期的干旱变化趋势不如南部农作物区和中部阔叶林带明显。农作物区9月、10月两月份干旱加重的趋势最显著,说明黄淮海平原区的夏玉米将越来越受到秋旱的威胁,防旱抗旱形势重于冬小麦面临的春旱,冬小麦的秋种受干旱的影响将加重。

Ten-day precipitation datasets of the meteorological observation stations in the study area from 1960 to 2008 were used to calculate multi-scale（1 month,3 months and 12 months） Standardized Precipitation Index（SPI） sequences.The long-time scale evolution cycle and extent of the drought in the study area and three kinds of major land type area,i.e.,grassland,cropland and broad-leaved forest land are analyzed by applying moving average and moving standard deviation to SPI historical sequence.The variation and tendency of drought throughout the historical period were analyzed using linear regression method and the trend of line was forecasted.The characteristic differences of the tendency of drought for the three sub-regions were compared in 12 months.The result showed that the intensity and frequency of drought had a gradually serious trend and each month had a greater difference in tendency of drought.June and July had more precipitation than the historical period and the trends of drought in spring（April） and autumn（September and October） are more obvious.During the entire historical period,changing trend of drought in the grassland area is not as obvious as that in cropland of the southern study area and broad-leaved forest land of the central study area.The drought tendency of cropland is obvious in September and October.Summer corn in Huang-Huai-Hai Plain are faced with the threat of more and more autumn droughts,and the situation of droughts is more serious than that of the spring drought posing to winter wheat.The drought will exert greater impact on the autumn sowing for winter wheat.