Abstract
Urbanization in China has been expanding dramatically since 1978, significantly affecting the extreme temperature changes in cities, which is a vital indicator of urban climate change. To assess urban-related effect on regional extreme-temperature changes in China, this study employed high-resolution land use data to divide meteorological stations into rural stations, suburban stations, and urban stations, and evaluated the annual and seasonal changes in extreme minimum temperature (TNN), mean temperature (Tavg) and extreme maximum temperature (TXX) at each meteorological station. The result revealed that extreme temperature indices (TNN, TXX) and Tavg increased significantly from 1960 to 2016 with varied degrees in different seasons and different regions. Extreme temperature indices in high latitudes increased more rapidly than in low latitudes; while the trends in summer are slower than in other seasons. Urbanization effects on the trends of TNN, Tavg and TXX were all statistically significant, but urbanization effects on TNN and Tavg were more significant than TXX. The urbanization effects were more significant in low altitudes, especially in North, South, Northwest and Northeast China. In North, Northwest and Northeast China, the urban-related effects on temperature increase were mainly observed in spring and winter, but in South China, the urban-related effects were more evident in summer. This study is valuable for sustainable urban planning in China.
Highlights
Global warming is a hot scientific topic in climate change research [1,2]
Various studies have reported urban areas are warmer than their rural neighboring areas [12]. These studies about the urban effects on temperature trends were not aimed to identify extreme differences, nor to evaluate the Urban Heat Island based on some individual meteorological sites, but to look for variations to urban effects over a period of decades in large area based on mean values from many site records [13,14,15]
The data showed that there were the fewest meteorological stations with obvious TNN changes in spring, while most meteorological stations with obvious TNN change occurred in summer, followed by autumn and winter
Summary
Global warming is a hot scientific topic in climate change research [1,2]. Global warming has caused a large range of problems, including rising sea levels, increasing the frequency and intensity of extreme weather events, melting glaciers, etc. [3,4,5,6]. Contributors to global warming include solar variations [7], greenhouse gas emissions and land use changes [8,9], etc. The changes in greenhouse emissions and land use are closely related to the degree of urbanization. Various studies have reported urban areas are warmer than their rural neighboring areas [12] These studies about the urban effects on temperature trends were not aimed to identify extreme differences, nor to evaluate the Urban Heat Island based on some individual meteorological sites, but to look for variations to urban effects over a period of decades in large area based on mean values from many site records [13,14,15].
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