基于改进帕默尔干旱指数的中国气象干旱时空演变分析

近几十年来随着全球变暖的不断加剧,中国多地频繁发生干旱灾害,经济损失也越来越大,因而研究干旱的时空演变对社会经济发展具有重要的现实意义。论文基于改进帕默尔干旱指数(sc PDSI)分析了1961—2009年间年和四季干湿变化,并利用旋转经验正交函数(rotated empirical orthogonal function,REOF)探讨了中国气象干旱的时空演变特征。结果表明:1)近49 a来,整体上中国年和四季均呈显著变湿趋势,且均在20世纪70年代初期发生了由干变湿的突变;2)年及四季均存在2~8 a的振荡周期,其中夏季主周期为4.4 a,其余主周期均为6.2 a;3)根据REOF时空分解的前8个空间模态,将中国划分成8个干湿特征区域,其中大兴安岭地区、东南地区、西北地区和青藏高原南部地区有变湿趋势,后两个区域变湿趋势显著;东北—内蒙古高原区、青藏高原北部地区、中部地区和黄淮海平原地区呈变干趋势,前3个区变干趋势显著,黄淮海平原分区干湿变化不明显;各分区普遍具有2~9 a的振荡周期;4)极涡指数、印度洋偶极子和太平洋涛动与部分地区气象干旱有较好的相关关系。研究结果可为研究区防旱、抗旱与干旱预测提供参考依据。

Spatiotemporal variations analysis of meteorological drought in China based on scPDSI

Abstract: In recent decades, frequent droughts have been detected in some places in China along with the global climate change, which cause great damage to the development of social economy. Thus, it''s high time to investigate the spatio-temporal evolution of droughts. Based on the newly published scPDSI PM (self-calibrating Palmer drought severity index based on Penman-Monteith) dataset with high spatial resolution, the annual and seasonal variations of droughts in China from 1961 to 2009 were researched. Other research methods like linear regression, Mann-Kendall method, wavelet analysis as well as REOF (rotated empirical orthogonal function) were adopted to investigate the spatio-temporal pattern of droughts in China, and find out how droughts changed under the influence of the general circulation of atmosphere, in order to provide the foundation for drought control and drought resistance. The results indicated that: 1) In 1961-2009, China as a whole became moist significantly at annual and seasonal scale with the mutations of turning drought to wetness detected in early 1970s. 2) Period analysis illustrated that the oscillation period of seasonal and annual drought remained generally unanimous, and the dominant period of annual drought was 6.2 years, while drought in spring, autumn and winter generally had the periods of 2.6 and 6.2 years with 6.2 years as the dominant period; otherwise, drought in summer presented a dominant period of 4.4 years. 3) In the light of the spatial modes disassembled from REOF, the entire country was divided into 8 regions with different characteristics of drought or wetness, which were Northwest China, Northeast - Inner Mongolia Plateau area, the Greater Khingan Range area, the northern Qinghai-Tibet Plateau area, the southern Qinghai-Tibet Plateau area, the Middle China (including Sichuan Basin, Hanzhong Basin and Loess Plateau), Huang-Huai-Hai Plain and Southeast China. It was found that the sub-regions of REOF could primely manifest the geographical features of different regions, and hence objectively testify the actual drought condition in China. Among the 8 regions, the Greater Khingan Range area, Southeast China, the southern Qinghai-Tibet Plateau area, and Northwest China were getting moist while the latter 2 areas had a significant trend (P<0.05); Northeast - Inner Mongolia Plateau area, the northern Qinghai-Tibet Plateau area, the Middle China and Huang-Huai-Hai Plain were getting dry, and except Huang-Huai-Hai Plain, the former 3 regions were prominently getting dry. Take the regions as the objects, no matter at annual or seasonal scale, Northwest China was getting moist, while the Middle China was getting arid (P<0.05). Although the geographical positions of the 8 regions resulted in the discrepancy of influence under different climate factors, the 8 regions generally had the oscillation period of 2-9 years. 4) M-K test (Mann-Kendall test) on the 8 regions showed that the seasonal MK values of different regions varied with each other, which indicated that drought-wet degree of different regions had obvious seasonal feature, and yet most regions had a tendency of getting drought in spring and getting moist in summer. 5) Good correlations were found between polar vortex index and drought in most areas. Correlation analysis indicated that droughts in Northwest China may be affected by the polar vortex, Indian Ocean Dipole (IOD) and Pacific Oscillation (PDO). Droughts in Northeast - Inner Mongolia Plateau area, the Qinghai-Tibet Plateau area and the Middle China were significantly influenced by IOD, and drought of Huang-Huai-Hai Plain was negatively correlated with PDO. Unlike the conventional PDSI index, scPDSI integrates solar radiation and air speed into account, which will be of scientific and practical importance to forecast and distinguish different drought conditions.