黄河流域不同时间尺度干旱对ENSO事件的响应

利用黄河流域1963-2012年逐月气温和降水量数据,计算了各气象站点不同时间尺度的标准化降水蒸散指数(SPEI),通过对不同时间尺度SPEI与Niño 3.4区海洋表面温度距平(SSTA)的时空相关性进行分析,揭示不同时间尺度干旱对ENSO事件的响应及ENSO事件对黄河流域不同区域降水量和气温的影响。结果表明:(1)黄河流域1、3、6个月时间尺度的干旱在各时间段均有发生,12、24个月时间尺度的干旱主要发生在20世纪末和21世纪初的近20年。黄河上游和中游地区不同时间尺度的SPEI与SSTA均呈负相关关系,下游地区呈正相关关系。(2)黄河流域不同时间尺度的SPEI与SSTA相关性在空间分布上具有显著的差异性。久治站以上的黄河上游地区、中游地区的宁夏、内蒙古、陕西和山西的北部以及下游地区均呈正相关关系,其余地区呈负相关关系。全流域1、3、6、12个月和24个月时间尺度的相关性系数通过0.05显著性检验的站点占总站点数分别为14%、43%、61%、75%和44%。(3)ENSO事件强度与降水量在黄河上游地区的相关性较弱,在中游和下游地区呈显著的负相关性,强度增大时降水量下降,减弱时降水量上升。全流域ENSO事件强度与气温呈显著的正相关性,强度增大时温度有上升趋势。其中El Niño对气温有抬高的趋势,La Niña对气温有降低的趋势。

Responses of Drought with Different Time Scalese to the ENSO Events in the Yellow River Basin

Drought disaster, one of the main natural disasters in China, impacts the people's lives and social production to different extends. Taking the Yellow River Basin as study area, standardized precipitation evapotranspiration index (SPEI) at different time scales were calculated using monthly temperature and precipitation data during 1963-2012. Temporal-spatial correlations between SPEI and the Nino 3.4 sea surface temperature anomaly (SSTA) of the different time scales reveal the response of drought (SPEI) to the ENSO at different time scales and the impacts of ENSO to regional precipitation and temperature in the Yellow River Basin. (1) Droughts of 1, 3, 6 months' time scales in the Yellow River Basin occurred in each time segment. Droughts of 12, 24 months' time scales mainly occurred in late twentieth century and early twenty-first century in recent 20years. There is a negative correlation between SPEI at different time scales and SSTA in the upper and middle reaches of the Yellow River Basin, while positive correlation in lower reaches. (2) Correlations between SPEI at different time scales and SSTA show large spatial heterogeneity in the Yellow River Basin. Positive correlation mainly is distributed in the upper reaches of the Yellow River Basin, Ningxia, Inner Mongolia, Shaanxi and Northern Shanxi, and the lower reaches of the Yellow River Basin, and the rest are negative correlation. The significant (at significant level of 0.05) proportions of the whole basin at 1, 3, 6, 12 months and 24 months' time scales were 14%, 43%, 61%, 75% and 44% respectively. (3) The weak correlation of ENSO event intensity and precipitation occurred in the upper reaches of the Yellow River, and there was a remarkable negative correlation in the middle and lower reaches. It indicated that the enhanced ENSO would reduce the precipitation and vice versa. Temperature showed a significant positive correlation with ENSO, and the enhanced ENSO would raise the temperature. The El Ni o would raise the temperature, and the La Ni a would reduce the temperature.