Abstract:

Under the background of global change, extreme high-temperature events have occurred frequently, and their frequency has increased significantly since the 21st century, which has a profound impact on agricultural production and human health. To explore the spatiotemporal evolution patterns of extreme high temperatures in the Yili River Basin with complex terrain, this study calculated six extreme high-temperature indices, namely summer days (SU25), hot night days (TR20), warm days (TX90p), warm nights (TN90p), extreme maximum value of daily maximum temperature (TXx), and extreme maximum value of daily minimum temperature (TNx), based on daily temperature data from 11 meteorological stations in the basin during 1991-2020. Through linear trend analysis, Mann-Kendall abrupt change test, Empirical Orthogonal Function (EOF) decomposition, and Kriging interpolation method, the spatiotemporal variation characteristics of these six extreme high-temperature indices in the Yili River Basin were systematically analyzed. The results show that most extreme high-temperature indices in the Yili River Basin have exhibited an overall rapid growth trend and underwent significant abrupt changes from the 1990s to the early 21st century. Among them, the growth rates of SU25, TX90p, TXx, and TNx are particularly prominent, and all indices entered an accelerated growth stage after 2015. In terms of spatial distribution, most extreme high-temperature indices in the basin present an obvious pattern of “high in the northwest and low in the southeast”: the northwest region is a high-value area for high-temperature indices, while stable low-value centers are formed in the northeast of Zhaosu, Tekes, Gongliu, and the southwest of Nileke. Through EOF decomposition, the spatial distributions of TXx and TNx exhibit two typical modes, and their evolution characteristics are highly consistent with the overall variation trend of extreme high temperatures in the basin.

Key words: the Yili River Basin, extreme heat, Empirical Orthogonal Funcion（EOF） spatial mode, spatio-temporal differentiation, abrupt characteristics

摘要：

在全球气候变化背景下，极端高温事件频发，且自21世纪以来其发生频率明显增加，对农业生产及人体健康造成深远影响。为探究地形复杂的伊犁河流域极端高温时空演变规律，本文利用1991—2020年该流域11个气象站逐日气温数据，计算夏季日数（SU25）、热夜日数（TR20）、暖昼日数（TX90p）、暖夜日数（TN90p）、日最高气温极高值（TXx）和日最低气温极高值（TNx）6个极端高温指数，并通过线性趋势分析、Mann-Kendall突变检验、经验正交函数分解（Empirical Orthogonal Function decomposition，EOF）以及克里金插值法（Kriging），系统分析伊犁河流域6个极端高温指数的时空变化特征。 结果表明：伊犁河流域大部分极端高温指数整体呈快速增长趋势，且在20世纪90年代至21世纪初发生显著突变。其中SU25、TX90p、TXx和TNx的增长速率突出，2015年后各指数处于加速增长阶段。空间分布上，流域大部分极端高温指数呈现明显的“西北高、东南低”格局：西北部为高温指数高值区，昭苏东北部、特克斯、巩留及尼勒克西南部形成稳定低值中心。由EOF分解得到TXx与TNx的空间分布存在两种典型模态，其演变特征与流域极端高温整体变化趋势具有高度一致性。

关键词: 伊犁河流域, 极端高温, EOF空间模态, 时空分异, 突变特征