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1980~2019年成都夏季极端高温事件与其干湿热的时空分布特征

Spatiotemporal Distribution Characteristics of Summer Extreme Heat Events with Dry and Humid Heat Days in Chengdu during 1980–2019

  • 摘要: 基于1980~2019年成都14个国家气象观测站的逐日气温、气压和相对湿度等数据,统计5类极端高温指标分析成都夏季极端高温的变化,并将成都夏季极端高温分为极端干热型和极端湿热型,利用经验正交函数和傅里叶分解等方法对比分析两者的时空分布特征。结果表明:1980~2019年成都夏季极端高温主要呈西北少、东南多,由西北向东南递增的空间分布;极端高温的强度、频次和持续性在空间分布上有一定差异,成都的西北部和中西部虽有高温天气出现但不易形成持续性的热浪,西部和北部的高温天气更易以持续性的热浪发生,东部和南部则是较强高温热浪的频发区;40年里成都夏季极端高温呈增长趋势并多出现在7月和8月,2006年和2016年为成都夏季极端高温较强的年份。同时,成都夏季的极端高温以极端湿热型为主,且呈增长趋势;过去40年成都极端湿热的增幅整体大于极端干热;极端干热存在2种模态的空间分布型,分别为全区一致型和纬向“三极子”型,相应的时间系数分别在90年代中期和2000年以后出现年际和年代际变化特征;极端湿热主要呈现全区一致的变化特征,对应的时间系数呈增长趋势并有明显的年际和年代际变化特征。

     

    Abstract: Based on daily observational data (e.g., temperature, air pressure, and relative humidity) collected from 14 ground meteorological stations in Chengdu, the spatial distributions and temporal variations of summer extreme heat events by calculating five indices of extreme heat events during 1980−2019 were investigated. In addition, the characteristics of extremely dry and humid heat days were analyzed by using the Empirical Orthogonal Function (EOF) and Fourier decomposition methods. The results reveal that the summer extreme heat events have been more frequent in the southeastern area of Chengdu than in its northwestern area. Furthermore, an increasing tendency of heat extremes is observed from northwest to southeast across Chengdu during 1980−2019. The magnitude, frequency, and duration of the extreme heat events exhibit spatial heterogeneity. In particular, hot days occur more than heat waves in the northwest and mid-west of Chengdu, while heat waves are more prevalent in the western and northern parts. The extreme hot days and heat waves are mainly concentrated in the eastern and southern regions of Chengdu. Over the past four decades, Chengdu has witnessed a significant increase in summer extreme heat events, notably in July and August, with the most severe instances occurring in 2006 and 2016. The summer extreme heat events were dominated by the humid heat extremes across Chengdu during 1980−2019. Extreme humid and dry heat days exhibited increasing trends, with the humid heat extremes growing faster than dry heat extremes during this period. EOF analysis indicates two primary modes for extreme dry heat days: The first mode is a homogeneous pattern with obvious variations after the mid-1990s, while the second mode is a zonal tripolar pattern with considerable variations after 2000. The leading EOF mode of extreme humid heat days displays a homogeneous pattern with discernible interannual and interdecadal variations.

     

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