Effect of urban expansion on atmospheric humidity in Beijing-Tianjin-Hebei urban agglomeration

Xin Li; Wenyou Fan; Lunche Wang; Ming Luo; Rui Yao; Shaoqiang Wang; Lizhe Wang

doi:10.1016/j.scitotenv.2020.144305

Effect of urban expansion on atmospheric humidity in Beijing-Tianjin-Hebei urban agglomeration

Sci Total Environ. 2021 Mar 10:759:144305. doi: 10.1016/j.scitotenv.2020.144305. Epub 2020 Dec 9.

Authors

Xin Li¹, Wenyou Fan¹, Lunche Wang², Ming Luo³, Rui Yao¹, Shaoqiang Wang¹, Lizhe Wang⁴

Affiliations

¹ Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China; Hubei Key Laboratory of Critical Zone Evolution, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China.
² Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China; Hubei Key Laboratory of Critical Zone Evolution, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China. Electronic address: wang@cug.edu.cn.
³ School of Geography and Planning, Guangdong Key Laboratory for Urbanization and Geo-simulation, Sun Yat-sen University, Guangzhou, China.
⁴ School of Computer Science, China University of Geosciences, Wuhan 430074, China; Hubei Key Laboratory of Intelligent Geo-Information Processing, China University of Geosciences, Wuhan 430074, China.

PMID: 33340859
DOI: 10.1016/j.scitotenv.2020.144305

Abstract

Accelerated urban expansion has contributed to the urban-rural contrast regarding atmospheric humidity. However, the effect of urban expansion on atmospheric humidity is not understood well in the Beijing-Tianjin-Hebei urban agglomeration (BTHUA). In this study, observations from 133 meteorological stations were used to analyze the long-term trend of atmospheric humidity and the urban expansion effect in the BTHUA during the period 1961-2014. The urban expansion effect on atmospheric humidity was evaluated by calculating the differences in atmospheric humidity trends between urban and rural series based on the dynamic classification method using secular urban impervious data. The results revealed that a drying trend of annual and seasonal average atmospheric humidity was observed in the urban areas of the BTHUA during the period 1961-2014, characterized by decreasing relative humidity (RH), water vapor pressure (E_a), specific humidity (Q) and increasing vapor pressure deficit (VPD). A more prominent drying trend (p < 0.05) appeared in spring and autumn, whereas a relatively weaker trend occurred in summer and winter. The trend of atmospheric humidity was significantly correlated (Spearman correlation coefficients: -0.45, 0.48, -0.29 and -0.32 for RH, VPD, E_a and Q, respectively; p < 0.01) with the urban expansion rate. The effect of urban expansion on the trend of VPD, E_a and Q was the strongest in spring at 0.138 hpa, -0.237 hpa and -0.151 hpa per decade, respectively, while the urban expansion effect on RH was the strongest in winter, reaching -1.159% per decade. This study provides a better understanding of the relationship between variations in atmospheric humidity and urban expansion, as well as scientific support for urban planning.

Keywords: Atmospheric humidity; Beijing-Tianjin-Hebei urban agglomeration; Drying atmosphere; Urban expansion effect.