气候变暖背景下中国西南干旱时空分异特征

Temporal-spatial abnormity of drought for climate warming in Southwest China

基于相对湿润度的干旱指数,应用1958-2012年中国西南89个国家基本气象站逐日气象资料,研究中国西南干旱时域变化、空间分布和次区域时空演变特征。结果表明:1958-2012年西南平均干旱区域占总面积的30%左右,川西高原、川西南山地和云南中北部区域干旱发生频率在60%以上,大部分区域干旱强度呈增加趋势。EOF mode 1反映出西南区域干旱强度振荡的位相相同;云贵高原中部易出现异常干旱、振荡强度大且敏感。EOF mode 2特征向量场北部与南部呈反相位分型特征,其形成机制是南部片区的云南高原和贵州高原偏南地区主要受南亚季风影响,而北部片区的四川、重庆和贵州偏北地区主要受青藏高原季风、东亚季风的影响。依据REOF特征向量场结构类型,将研究区域划分为4个次区域;"川西高原异常型"干旱强度显著减弱,由干变湿的突变点在1987年。"四川北部异常型"干旱强度显著增强,由湿变干的突变点在1968年。"云南高原异常型"和"贵州高原异常型"干旱指数均呈波动下降趋势,但未通过显著性检验。

Drought index analytical methods based on the relative moisture index were used to study temporal variation spatial distribution and sub-regional evolution characteristic of drought in southwest China using meteorological data from 1958 to 2012. The results show that the average drought area in recent 55 years covers 30% of the total area in southwest China.Some regions on the West Sichuan Plateau, Southwest Sichuan Upland and north and central regions in Yunnan have a drought appearance frequency of up to 60%. The negative absolute value of the relative humidity index in these regions increased over time and drought intensity increased. Components in most regions of the EOF first modality feature vector are negative, indicating that oscillation phases of drought intensity in most southwestern parts are the same. High load regions of each component are focused in the central part of Yungui Plateau, and this region is the area where abnormal drought would be easier to appear with a higher oscillation intensity and sensitivity among all spatial types. The EOF second modality feature vector field showed an opposed phase character because the, southern part including the Yunnan Plateau and south Guizhou Plateau are mainly influenced by the south Asian monsoon while the northern part including Sichuan, Chongqing and north Guizhou are mainly influenced by the Tibetan Plateau monsoon and east Asian monsoon. According to different modality and spatial distribution of REOF feature vector field, the studied region is divided into four sub-regions. West Sichuan abnormal type had obvious decreased drought intensity and catastrophe point from dry to wet was in 1987. Drought intensity of the North Sichuan abnormal type has increased and the catastrophe point from wet to dry was in 1968. The Yunnan Plateau abnormal type and Guizhou Plateau abnormal type have, a decreasing drought index had decreasing trend with fluctuation, but failed to pass a significance test.