Spatiotemporal Changes of Extreme Temperatures in the Past 49 Years and Their Relationship With the Enso in Southwestern China

In the present research, spatiotemporal changes of extreme temperatures in Southwestern China as well as their relationship with the El Nio-Southern Oscillation (ENSO) events were determined for the 1969 to 2017 period using the Mann-Kendall test, the Sen's slope estimator, and the empirical orthogonal function (EOF) analysis. For this purpose, daily temperature data of 93 weather stations and 17 extreme temperature indices (ETIs) were analyzed. Our results suggested that: (1) during the past 49 years, ETIs showed a warming trend in Southwestern China, and differences in warming trends were observed in different geographical regions. (2) In the 1990s and early 21 st century (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011), abrupt extreme temperature changes were observed. (3) Results of the EOF analysis also indicated abrupt changes in extreme temperature indices. The regions susceptible to changes in the number of ice days (ID) were the Hengduan Mountains and part of the Yunnan-Guizhou Plateau. The high-value midpoints of summer days (SU) were found in the Zoige Plateau, Sichuan Basin, and part of the Yunnan-Guizhou plateau. (4) The ETIs were closely related to the ENSO events. The extreme cold indices were more significantly influenced by La Nia, and the extreme warm indices were more susceptible to El Nio events.