A new method to retrieve aerosol optical depth over land using MODIS data

In this study, a new method was proposed to retrieve aerosol optical depth at 0.55μm (AOD_0.55μm) using MODIS images with the second simulation of satellite signal in the solar spectrum model (6S). Provided that surface features have little change in a short period, the surface reflectance ratios between visible and infrared bands pixel-by-pixel can be calculated directly using satellite image on clean day when aerosol optical depth is too small enough(AOD<;0.01) to be neglected comparing with dust day. Then, the stable ratios are used to retrieve aerosol optical depth on dusty day. Experiments were conducted to retrieve AOD_0.55μm over the west coast of Bohai. For validation, AOD derived by the method was compared with measurements from Aerosol Robotic Network (AERONET). The relative error range was within 20%, which demonstrated that the method can be used to not only dark object but also bright regions well, particularly over urban regions.