Viewing Global Megacities Through MODIS $4\hbox{-}\upmu \text{m}$ Radiance: Effects of Time of Year, Latitude, Land Cover, and View Zenith Angle

Cities are often obscured by haze and smoke when viewed in the visible and near infrared, but the longer wavelengths of the middle infrared can penetrate fine aerosol layers. We characterized variation in 4-μm radiance in and nearby eight global megacities using MODIS band 23 calibrated radiance. The seasonality of middle infrared (MIR) radiance was more pronounced at higher latitudes. Precipitation attenuated MIR radiance. The seasonality of MIR radiance from exposed soils was very similar to urban surfaces, complicating discrimination. The variety of urban surfaces across the megacities also affected the seasonality of MIR radiance. Additional data and MIR radiance with higher spatial resolution could improve and refine/detail information about MIR radiance behavior for further investigation.