Consideration of Aerosol Effects and Atmospheric Correction Method on AVHRR Images around Japan
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概要
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We study the method of atmospheric correction of AVHRR images, with a particular emphasis placed on the aerosol effects. First, the correction of molecular effect is examined by comparing the difference between the reflectances obtained using the 6S model profile and the observed atmospheric profile. Since the ozone amount observed in winter is considerably less than that in the winter model, the tropical model with small ozone amount is selected as an optimum model. Therefore, observed atmospheric parameters of temperature, atmospheric pressure, ozone amount, and water vapor content are employed in the analysis of the aerosol effect. The atmospheric correction is first carried out in terms of the ground visibility, and the accuracy of the correction is examined for ocean, urban and forest areas. For the ocean areas, the process yields negative values of the reflectivity, indicating an overcorrection. Then, the relationship among the ground visibility, aerosol optical thickness, and the 6S model profile is examined. It turns out that when the optical thickness is computed from the visibility using the 6S code, the resulting value is twice as much as the observed value. This indicates that in order to carry out the atmospheric correction with a good precision, it is necessary to estimate good aerosol models and optical thickness from the ground level to the top of the atmosphere. Thus, in a second approach, we investigate the possibility of atmospheric correction using the bimodal, lognormal distributions with accumulation and coarse particle modes. Size distributions are estimated from sea area images. After the atmospheric correction, the results are quite reasonable for dark pixels such as the forest areas, while improvements are still needed for highly reflective pixels.
- 社団法人 日本リモートセンシング学会の論文