基于日值SPEI的青藏高原干旱演变特征

Drought evolution characteristics on the Tibetan Plateau based on daily standardized precipitation evapotranspiration index

利用1980-2014年青藏高原74个台站的气象资料,通过Penman-Monteith公式计算了蒸散发及标准化降水蒸散指数(SPEI),并采用M-K趋势分析和小波分析等方法研究了高原干旱变化的时空分布特征及变化趋势。结果表明,基于Penman-Monteith公式计算潜在蒸散发的逐日SPEI指数能够很好地反映青藏高原干旱特征。1980年以来青藏高原SPEI值总体呈上升趋势,即偏于湿润,干旱强度有所降低。高原近35年的干旱演变具有明显的年代际差异,20世纪90年代之前干旱较为严重。小波分析结果表明高原干旱的发生存在2～4 a的振荡周期,在2～4 a的时间尺度上总体表现出干-湿周期变化。在整体小波变化周期中,1983-1997年虽然出现了干旱严重区间,但在1997年以后高原总体上呈现湿润趋势,3. 7 a的主周期并没有影响整体变湿的趋势,且三种指标的3. 7 a振荡主周期均通过了95%的红噪声检验。

According to the data of temperature and precipitation from 74 weather stations on the Tibetan Plateau from 1980 to 2014 and combining the Penman-Monteith formula, the evapotranspiration and the standardized precipitation evapotranspiration index (SPEI) have been calculated. The M-K trend analysis, mutation analysis and wavelet analysis have been used to analyze the spatial and temporal variation of SPEI on the Tibetan Plateau. The results show:(1) The daily SPEI based on the Penman-Monteith formula can well reflect the drought characteristics of the plateau. Since 1980, the SPEI on the plateau has increased, that is, partial to the wet and the drought intensity decreased. (2) The drought on the plateau in the past 35 years had obvious interdecadal variation, drought had been more severe before the 1990s;M-K mutation analysis showed that a mutation occurred in 1990, the severity and duration of drought had reduced after the 1990s. (3) Wavelet analysis revealed that there was a 2-4 years oscillation period of plateau drought. The dry-wet period had changed overall with a time scale of 2-4 years;there were three indicators in the 3.7 years primary period all passing 95% red noise test.