We present the retrieval algorithm of aerosol optical thickness over the land area. The algorithm is based on the dark-target approach combined with the texture analysis. In the first part of the algorithm, we employ the 6S code to calculate the relevant radiance components. The aerosol optical thickness is retrieved over the sea surface assuming a surface reflectance of 0.02. Two-dimensional linear interpolation is applied to tentatively determine the optical thickness over the land area that is surrounded by the sea area. In the second part, a difference image is calculated between an actual satellite image (turbid image, NOAA AVHRR channel 1 on December 1, 1997) and a clear image that is obtained by applying the atmospheric correction to a satellite image (December 15, 1997). The atmospheric feature included in the difference image is then analyzed by the texture analysis. For each area that includes both land and sea surfaces, and is categorized into a texel (i.e. its atmospheric feature is considered to be uniform), the optical thickness of the land area is assumed to be the same with that over the sea area. In addition, we present a Taerosol model on the basis of the ground measurements conducted at 11 sites on the Kanto plain during December 22 to approximately 24, 1997. In this model, chemical composition data are used to derive the single scattering albedo and the asymmetry parameter. These optical parameters are useful to improve the accuracy of the radiation calculation with the 6S code.