Impacts of spatial clustering of urban land cover on land surface temperature across Koppen climate zones in the contiguous United States

This study examines the effects of spatial clustering of urban land cover types on land surface temperature (LST). The potential impact of the background regional climate is also taken into consideration. To study this relationship, multiple cities, each representing a major Koppen climate region in the U.S., namely Portland, Los Angeles, Chicago, Denver, Kansas City, Orlando, and Phoenix, were selected. Urban land cover types were derived from the 2011 National Land Cover Database (NLCD); summer mean LST from 2011 was calculated using the Moderate Resolution Imaging Spectroradiometer (MODIS) LST products. Spatial clustering was quantified using Moran's I, and was analyzed against LST using correlation and multivariate regression analyses. The results indicate that in most climate regions, clustered impervious surfaces can elevate LST for both daytime and nighttime. The cooling effect of clustered vegetation cover was only found significant in regions with dry and warm summers, such as in Phoenix and Portland. Clustered water bodies have a strong cooling effect during the daytime but have a warming effect at night, except for cities such as Los Angeles and Phoenix, which have scant large water bodies. Furthermore, policy recommendations were put forward to suggest that reducing the spatial clustering of impervious surfaces, having more spatially clustered greenspaces, and having spatially dispersed water bodies with clustered greenspaces nearby are potential strategies to reduce urban warming in most cities in the contiguous U.S.