近半个世纪中国西北干湿演变及持续性特征分析

Influence research on spring vegetation of Eurasia to summer drought-wetness over the northwest China

利用1960-2007年中国西北地区248个气象台站的逐日降水、温度资料,通过降水和潜在蒸发均一化干湿指数,从年际演变、季节内变化以及持续性特征等方面较系统地揭示了近半个世纪来西北地区的区域性干湿演变事实,结果表明:在温度与降水双重因子驱动下西北地区的干湿演变特征同降水单一要素驱动下的干旱特征存在明显的差异,说明气候变暖对西北干旱化趋势的贡献程度比较显著;自20世纪90年代后期以来,西北各分区每年异常干旱月份发生概率呈增多趋势,而异常湿润月份发生概率除了北疆地区外,其它分区近10 a异常偏少,这种现象在西北东南部表现得尤为突出。从四季干湿变化来看,冬季表现为湿润化趋势,而春、夏、秋三季呈现出了干旱化趋势。另外西北东南部、青海高原东侧以及南疆地区自20世纪90年代以来,很少出现过持续性湿润事件,而持续性干旱事件却明显多于90年代以前,而且持续性干旱的最长持续时间长,强度大,北疆地区和青海高原48 a来持续性干湿事件发生频次、强度以及持续时间没有明显的趋势变化,而青海高原地区相比其它区域持续性干湿事件偏少,强度偏弱,最长持续时间也偏短。

Using temperature and precipitation data of 248 stations in Northwest China, from interannual change, in- terseasonal variability and durability characteristic posted regional drought and wetness evolvement over Northwest China in recent half century by homogenized drought - wetness index of precipitation and evaporation. The result showed that drought -wetness evolvement characteristic exist clear difference between driven by temperature and precipitation and driven by precipitation, this illuminated that contribution of climate warming to drought trend of Northwest China is marked. ＇Since 1990 anaphase probability of abnormal drought month showed increase trend in every subarea, but that of abnormal wetness month lean to fewness in recent 10 years except for North Xinjiang, and the phenomenon is especially stand out for southeast of Northwest China. From season view, winter could hardly oc- cur abnormal drought phenomenon in mostly area of Northwest of China, but it showed drouthy trend in spring, sum- mer and autumn, in additional since 1990 durative wetness event had hardly occurred in southeast of Northwest Chi- na,east of Qinghai tableland and south of Xinjiang, and durative drought event much more than that of before 1990s, and maximal duration was long,intensity was also strong,frequency, intensity and duration of north of Xinjiang have not clear trend change in recent 45 a, in despite of frequency of durative drought than that of durative wetness in Qinghai tableland,but it was fewer than that of other area＇s, and intensity was waeker, duration was short.