Linking between Urbanization and Cloud Coverage Trends in East Asia

Urbanization processes may significantly modify the atmospheric properties by changing the surface albedo, altering the sensible and latent heat balance, and increasing emissions of both heat and anthropogenic aerosols. In this study, we focus on East-Asia, which is one of the most densely and rapidly economically growing areas, in order to explore the connection between extensive urbanization processes and cloud properties.

For this purpose, a 14 yearlong dataset of the Multi-angle Imaging SpectroRadiometer (MISR) aerosol and cloud products is co-located with the land usage product of the Moderate Resolution Imaging Spectroradiometer (MODIS). Analysis of both cloud fraction (CF) and CF of low clouds in East-Asia shows a decrease over the observed domain, with an average of ~-0.2 %/yr and ~-0.4 %/yr, respectively. Closer observation shows that these trends are different in urbanized regions, when the overall mean values of lower clouds CF inside urbanized areas is 27%±4% lower than in rural areas. Similar analyses for other densely populated regions (e.g. India, US east-coast, and Europe) did not find clear difference in the mean CF values between urbanized and rural environments. We suggest a combined dynamical and microphysical mechanism to explain this unique link, as observed in East Asia.