Dvorak technique
Over land the retrieval of temperature from radiances is harder, because of inhomogeneities in the surface. Studies have been conducted on the urban heat island effect via satellite imagery. Use of advanced very high resolution infrared satellite imagery can be used, in the absence of cloudiness, to detect density discontinuities (weather fronts) such as cold fronts at ground level. Using the Dvorak technique, infrared satellite imagery can be used to determine the temperature difference between the eye and the cloud top temperature of the central dense overcast of mature tropical cyclones to estimate their maximum sustained winds and their minimum central pressures.