西南地区旱涝演变与ENSO事件的关系

在气候变化大背景下,西南地区旱涝频发,而ENSO（厄尔尼诺-南方涛动）是气候变化的重要指示性因子。本文利用海表温度距平（SSTA）、南方涛动指数（SOI）、西南地区近57年的降水和气温数据,运用小波分析和数理统计方法,分析ENSO事件与降水、气温及旱涝指数的相关关系。结果表明：①ENSO事件存在9 a、24 a和3~4 a左右的准周期变化。②降水量、气温与ENSO事件强度存在比较明显的相关关系,且存在一定的滞后性;在EI Nino（厄尔尼诺）事件发生的年份,西南地区的降水、气温与SSTA在滞后2~4个月时呈显著负相关;在La Nina（拉尼娜）事件发生的年份,西南地区的降水、气温与SSTA在滞后2~4个月时呈显著正相关关系;气温同ENSO事件相关关系更为明显。③ENSO事件强度与旱涝等级存在一定的负相关关系,当EI Nino事件强度增大时对应西南地区的干旱事件增多;当La Nina事件强度增大时,西南地区洪涝事件增多;旱涝指数SPI和SOI也呈极显著的负相关关系,SOI对旱涝的影响存在1~4个月的滞后期,并且在滞后3个月时影响最大。因此,西南地区在强ENSO事件发生的当年或次年易发生旱涝灾害,需要提高对旱涝事件的警惕,加强防汛抗旱工作。本文结果可为西南地区防汛抗旱工作提供参考。

Relationship between drought/flood and ENSO events in Southwest China

Under the background of climate change, drought and flood occur frequently in Southwest China, and El Nino and Southern Oscillation (ENSO) is an important indicator of climate change. Based on the data of sea surface temperature anomaly (SSTA), Southern Oscillation Index (SOI), precipitation, and temperature during 1960-2016 in Southwest China, the correlation between ENSO events and precipitation, temperature, and drought/flood index was analyzed by using wavelet analysis and mathematical statistics. The results show that: (1) The ENSO events have quasi-periodic changes of about 9 a, 24 a, and 3~4 a. (2) There is a significant correlation between precipitation and ENSO event intensity, and temperature is also obviously correlated with ENSO event intensity, both with a certain lag of time. In the EI Nino event years, the precipitation and temperature in Southwest China are negatively correlated with SSTA with a lag of 2~4 months. In the La Nina event years, the precipitation and temperature in Southwest China are significantly positively correlated with SSTA with a lag of 2~4 months. The correlation between temperature and ENSO events is more obvious. (3) There was a negative correlation between the ENSO intensity and drought/flood grade. When the EI Nino event intensity increased, the number of drought events in the southwest region increased, and when the intensity of La Nina events increased, the number of flood events in the southwest region increased. The drought/flood index of Standardized Precipitation Index (SPI) and SOI also showed a very significant negative correlation, and the impact of ENSO on drought and flood had a lag of 1~4 months, with the greatest impact at 3 months lag. Therefore, drought and flood disasters are likely to occur in strong ENSO event years or the following year in the southwest region. This study may provide some reference for enhancing the vigilance against droughts/floods and strengthen flood control and drought relief work in Southwest China.