A retrieval algorithm for aerosol optical depth from MODIS multi-spatial scale data based on mutual information

A retrieval algorithm for AOD from MODIS multi-spatial scale data with 1 km × 1 km, 500 m × 500 m and 250 m × 250 m resolution based on mutual information (MI) is proposed. The concept of mutual information represents a measure of relative entropy between two sets. In this algorithm, an interpolation formula based on the maximal MI which is used to transform low resolution image into high resolution image is constructed. Then, the AOD with 500 m × 500 m and 250 m × 250 m resolution which are over Heihe Watershed, in Gansu province, China, on 5^th July, 2008 are retrieved from TERRA and AQUA MODIS data. Compared with the 500 m × 500 m AOD retrieved by multi-satellite algorithm directly, the AOD with 500 m × 500 m resolution got by the MI algorithm is coincident with absolute error between 0.02-0.03. Preliminary validation result comparing with AERONET measured data shows good accuracy and promising potential. The Further research work is ongoing.