【摘要】 黄土高原作为气候变化敏感区和生态脆弱区,干旱对本区的生态环境和经济发展产生了影响深远,分析本区干旱变化规律对保障农业生产安全,维护生态系统的健康具有重要的意义。本文基于1958—2015年夏季降水和气温格点数据,以及热带海洋温度气候指数,运用标准化降水蒸散指数(SPEI)、经验正交函数分解(EOF)、小波分析、交叉小波分析等方法,分析了黄土高原夏季干旱的时空分布类型、周期变化特征,并且讨论了SEPI与热带海温的协同关系。结果表明高原夏季SPEI的EOF第一模态表现为整体一致型变化,方差贡献为32.6%,第二模态主要表现为高原东南一西北反向变化的特征,其方差贡献为16.9%,前两个模态的总方差贡献可达到49.5%。第一模态时间序列(PC1)主要表现为2-4 a周期变化,是黄土高原夏季SPEI的主周期;第二模态时间序列(PC2)存在两个周期,即2-3a和8-10a;根据交叉小波分析,这两个模态受外强迫因子的调制作用上可能存在较大的差别。黄土高原SPEI平均水平在各个时段表现出了很大的差异性,其中1978-1992年和1993-2005年两段时期干旱的分布区域有明显扩大的趋势;2006-2015年极端干旱在甘肃东部表现特别明显,在这段时期黄土高原旱涝分布的差异性较为突出。黄土高原夏季中度、重度、特旱等级的发生的频率主要在内蒙古和宁夏,此外在平原河谷地带,诸如渭河平原和太原盆地的SEPI明显低于周边地区,干旱发生的频率也显著高原周边,形成了高原上的干谷。综上所述,基于SPEI对黄土高原地区干旱进行了多尺度的时空分解,刻画了干旱的基本特征,并初步讨论了干旱的成因,研究结果可为本区干旱预警及生态保护和修复提供科学依据。更多还原

【Abstract】 As a sensitive area of climate change and ecologically fragile area,drought has had a far-reaching impact on the ecological environment and economic development of the Loess Plateau.It is of great significance to analyze the law of drought evolution for ensuring the safety of agricultural production and maintaining the health of the ecosystem in this area.Based on the daily precipitation and temperature(1958-2015 in summer),and the tropical oceanic climate index,the spatial-temporal distribution types and periodic variation characteristics of the summer drought in the Loess Plateau is analyzed,and the synergistic relationship between SEPI and tropical SST is also discussed by using the standardized precipitation evapotranspiration index(SPED),empirical orthogonal function decomposition(EOF),wavelet analysis and cross-wavelet analysis.The results show that the first mode of EOF of SPEI in summer on the plateau shows a uniform change with variance contribution of 32.6%,and the second mode mainly shows a reverse change from southeast to northwest of the plateau with the variance contribution of 16.9%,and the total variance contribution of the two modes can reach 49.5%.The period of the first modal time series(PC1)is 2-4 a,which is the main period of SPEI in summer on the Loess Plateau.The second mode time series(PC2)has two periods,i.e.2-3 a and 8-10 a.According to cross-wavelet analysis,the two modes may be modulated by different external forcing factors.The average SPEI values in the Loess Plateau shows great differences in different periods,of which the distribution in 1978-1992 and 1993-2005 has an obvious trend of expansion;extreme drought in 2006-2015 in eastern Gansu is particularly evident,during this period,the distribution of drought and flood in the Loess Plateau is more prominent.The frequency of moderate,severe and extreme drought in summer on the Loess Plateau is mainly in Inner Mongolia and Ningxia.In addition,the SEPI is significantly lower in Weihe Plain and Taiyuan Basin,and the frequency of drought is also significantly higher,forming a dry valley on the Loess Plateau.In summary,be based on the SPEI,a multi-scale spatial-temporal analysis of drought in the Loess Plateau is carried out.The basic characteristics of drought are depicted and the causes of drought are discussed.The research results could provide scientific basis for drought early warning,ecological protection and restoration in this area.更多还原