Urbanization Makes the Surrounding Atmosphere Drier

Researchers have long been aware of the effect of urbanization on making the surrounding climate hotter compared to adjacent rural areas.  Researchers also wanted to look at the impact of urbanization on atmospheric humidity.  To do this, a recent study looked at changes to the  humid Yangtze River Delta region, which is undergoing rapid urbanization.

The Yangtze River Delta (YRD) region in southern China includes the rapidly urbanizing areas of Shanghai, one of the world’s largest cities; Nanjing, and Hangzhou.  For the study, land use and land cover (LULC) change was analyzed between 2001-2014 using Landsat TM/ETM+ images. Global Land Surface Satellite (GLASS) LAI data sets were used to determine vegetation change from 2001 to 2014.  The study pulled daily meteorological data from 33 standard weather stations across the YRD covering the years 1961–2014.


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Land use and land cover (LULC) change patterns in 2000, 2005 and 2010 in the Yangtze River Delta. Figure: Hao et al., 2018.

Land use and land cover (LULC) change patterns in 2000, 2005 and 2010 in the Yangtze River Delta. Figure: Hao et al., 2018.

The data from theses sources was used to perform a correlation analysis to test the hypothesis that the loss of natural wetlands, forests, and paddies through urbanization results in reduced atmospheric humidity and elevated vapor pressure deficit, a phenomenon the researchers refer to as urban dry island (UDI) effects.  To this end, the researchers argue that “the role of vegetated land cover and associated ecohydrological processes in moderating UDI and maintaining a stable climate and environment should be considered in massive urban planning and global change impact assessment in southern China.

The study

Hao, L., Huang, X., Qin, M., Liu, Y., Li, W., & Sun, G. (2018). Ecohydrological Processes Explain Urban Dry Island Effects in a Wet Region, Southern China. Water Resources Research, 54(9), 6757-6771. https://doi.org/10.1029/2018WR023002

The Urban Dry Island Effect, Earth & Space Science News

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