Modeling of Anthropogenic Heat Flux Using HJ-1B Chinese Small Satellite Image: A Study of Heterogeneous Urbanized Areas in Hong Kong

Abstract

Anthropogenic heat is the heat flux generated by human activities and is a major contributor to the formation of an urban heat island. In a city such as Hong Kong, obtaining pure pixels from medium- or coarse-resolution remote sensing images is challenging. Considering the completely different thermal properties of vegetation and impervious surfaces, this letter developed a novel algorithm to estimate anthropogenic heat fluxes by decomposing image pixels into fractions of impervious surfaces and vegetation, and by estimating the total heat flux for the mixed pixel. The Chinese small satellite HJ-1B images with a spatial resolution of 30 and 300 m for visible and thermal wavebands, respectively, and the temporal resolution of four days were used for the heat flux modeling. Results show that anthropogenic heat fluxes in Hong Kong are correlated to the building density and the building height, with ${r}^{2} = \mbox{0.92} \text{and} \mbox{0.58} $ on October 11, 2012 and ${r}^{2} = \mbox{0.94} \text{and} \mbox{0.62} $ on January 13, 2013, respectively. The average anthropogenic heat fluxes in urban areas are 289.16 and 283.17 W/m2 on October 11, 2012 and on January 13, 2013, respectively, and the commercial areas emit the largest anthropogenic heat fluxes around 500–600 W/m2 compared with other land-use types. The derived anthropogenic heat fluxes can help in planning and environmental authorities to pinpoint “hot-spot” areas, and they can be used for compliance monitoring.