Comparison of aerosol models from the Ocean Color satellite sensors and AERONET-OC and their impact on reflectance spectra in coastal waters

Abstract

The choice of aerosol model in the atmospheric correction is critical in the process of the derivation of the water leaving radiances from the Ocean Color (OC) imagery for ocean monitoring. For the current sensors like MODIS, VIIRS and now OLCI atmospheric correction procedures include assumptions about the characteristics of atmospheric aerosols based on relative humidity and particle size distributions. At the sea level, SeaPRISM radiometric instruments which are part of the Aerosol Robotic Network (AERONET) make direct measurements of the water leaving radiances from the ocean, as well as observations of sky radiances from which aerosol parameters such as aerosol optical depth (AOD), fraction of fine and coarse aerosols and others are determined. The discrepancies between satellite and AERONET data are usually significant in coastal areas which are primarily due to the more complex atmospheres near the coast than in the open ocean. Using NASA SeaDAS software, characteristics of aerosols in atmospheric correction models for VIIRS and MODIS sensors are retrieved and compared with the ones from AERONET-OC data in terms of AOD, and remote sensing reflectance (Rrs) at the several AERONET-OC sites. The impact of the solar angles, scattering angles determined by the Sun-sensor geometry and wind speed on the differences in aerosols parameters are evaluated and correlated with the accuracies in the retrieval of the remote sensing reflectance spectra from ocean waters. Significant dependence of AOD on the wind speed is demonstrated which is most likely related to the modeling of the state of the ocean surface.