摘要:基于山东省15个气象台站1964—2010年的逐月降水和平均气温资料，采用标准化降水蒸散指数（SPEI）定量分析了山东省不同时间尺度干旱发生频率，利用Mann-Kendall非参数检验法和Arcgis软件，对近50年山东省干旱的时空变化趋势进行分析。为了研究厄尔尼诺/南方涛动（ENSO）对山东省干旱的影响，运用连续小波（CWT）、交叉小波变换（XWT）和小波相干谱（WTC）分析SPEI与ENSO指数（多变量ENSO指数，MEI）的相关关系和周期特征。结果表明：多时间尺度的SPEI值可以较好地反映山东省的干旱情况；不同时间尺度的SPEI值随时间变化的敏感性存在明显差异，时间尺度越小，变化幅度越大。近50年山东地区呈现明显的增暖趋势，其中东部增温最为显著，降水减少和温度升高使山东气候趋于"暖干化"，加剧山东省干旱程度。空间变化趋势上，山东省年SPEI和山东省年降水的空间分布具有一致性，总体有西部变湿润、东部变干的趋势。在干旱发生时间尺度上，月尺度干旱发生频率高于年尺度干旱发生频率，四季中春、秋季干旱最为严重。春旱和秋旱以鲁西和鲁西北平原发生频率最高，各地区之间差异明显。ENSO暖事件时，山东易旱；ENSO冷事件时，干旱减少。SPEI存在1~2.5 a尺度的年际振荡周期特征，呈现了与MEI指数相似的变化特征。高能量区，SPEI和MEI存在5~6 a的共振周期，SPEI较MEI提前1~2个月；低能量区，SPEI与MEI存在3~3.8 a呈负相位的共振周期。
关键词:山东省/
SPEI/
干旱/
ENSO事件/
多变量ENSO指数/
小波分析
Abstract:Drought is the most devastating natural disaster in the world. In recent years, prolonged droughts with huge impacts had caused enormous economic losses in China. Shandong Province belongs to a semi-humid climate, with complex and diverse underlying surfaces and sparse surface vegetation that is sensitive to climate change. Due to uneven distribution of precipitation during the year, drought and flood disasters in Shandong Province have been frequent, with significant impact on agricultural production and socio-economic development. Given the above, it was pivotal to study the spatial and temporal changes in drought in Shandong Province for application in drought monitoring and water resources management. Based on monthly precipitation and average temperature data from 15 meteorological stations in Shandong Province from 1964-2010, the frequency of drought at different time-scales in Shandong Province was quantitatively analyzed using standardized precipitation evapotranspiration index (SPEI). Using the Mann-Kendall non-parametric test method and Arcgis platform, the trends in temporal and spatial variation of drought in Shandong Province in the recent 50 years were analyzed. In order to study the impact of El Ni?o/Southern Oscillation (ENSO) on drought in Shandong Province, the continuous wavelet (CWT), cross wavelet transform (XWT) and wavelet coherence spectrum (WTC) were used to analyze the correlation between SPEI and ENSO index with the periodic characteristics. The results showed that SPEI at multiple time-scales reflected drought condition in Shandong Province. The sensitivity of time-varying SPEI was obviously different. The smaller the time-scale was, the greater the variation range was. In the recent 50 years, Shandong Province had an obvious warming trend, which was most significant in the eastern part of the province. Decrease in precipitation and increase in temperature induced warm and dry climate in Shandong, which aggravated drought conditions in the province. The spatial distributions of SPEI and annual precipitation in Shandong Province were consistent with the trend in spatial change, and the trend in the west had become more humid and in the east more dry. On the time scale of drought occurrence, the frequency of monthly drought was higher than that of annually drought, with spring and autumn having the most severe droughts across the four seasons. The highest frequency of drought occurred in West Shandong and Northwest Shandong Plain, with distinctive difference among different regions. With ENSO warm events, Shandong became prone to drought and ENSO cold events reduced droughts conditions. The annual-inter-annual oscillation cycle characteristics of SPEI was 1.0-2.5 years, showing similarity with the characteristics of Multiple ENSO Index (MEI). In high energy sector, the resonance period was 5.0-6.0 years for SPEI and MEI, but 1-2 months ahead of MEI. In low energy sector, there was a negative phase resonance period for SPEI and MEI of 3.0-3.8 years. The study provided a quantitative basis for understanding the spatial and temporal changes in drought in Shandong Province under global climate change. It also was helpful to decision-makers by improving preparedness and adoption of appropriate policies for agricultural management.
Key words:Shandong Province/
SPEI/
Drought/
ENSO event/
Multiple ENSO index/
Wavelet analysis
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