Investigating the effects of ocean bubbles on enhanced aqua-MODIS aerosol optical depth retrievals in the mid-to-high latitude southern oceans.

摘要

While satellite remote sensing aerosol measurements are widely used for climate, visibility and air quality studies, issues exist in the current satellite aerosol products such as the Elevated Southern Oceans Anomaly (ESOA) phenomenon. The ESOA is an elevated aerosol optical depth (AOD) belt over high latitude southern oceans detected by passive satellites such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR). The ESOA feature, however, is not present in the ground based studies. Cloud contamination was found to have a significant impact on this anomaly, but it is not the only contributor. Wind generated ocean bubbles could increase ocean surface reflectance. However, oceanic bubbles have not been considered in the conventional satellite aerosol studies. In this study, the effects of oceanic bubbles on satellite retrieved AOD values are studied using the linked 6S atmospheric and HydroLight oceanic radiative transfer models. The modeled Top-of atmosphere radiance values are evaluated using collocated observed MAN and MODIS retrievals. This study suggests that oceanic bubbles have an insignificant impact on AOD retrievals for regions with near surface wind speed less than 10 ms-1. However, under high wind scenario, the impact of bubbles to aerosol retrievals is significant and needs to be considered for future AOD retrievals using passive remote sensing techniques. Lastly, one year of MODIS and Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) data are used to investigate the impacts of oceanic bubble to the ESOA phenomenon. This study suggests that oceanic bubbles are not the major contributor to the ESOA feature.