부산대학교 도서관

An atmospheric correction algorithm has been developed for the Airborne Imaging Spectrometer for Applications (AISA) imagery over optically shallow waters in Sugarloaf Key of the Florida Keys. The AISA data were collected repeatedly during several days in May 2012, October 2012, and May 2013. Non-zero near-infrared (NIR) remote-sensing reflectance (Rrs) was accounted for through iterations, based on the relationship of field-measuredRrsbetween the NIR and red wavelengths. Validation showed mean ratios of 0.94–1.002 between AISA-retrieved andin situ Rrsin the blue to red wavelengths, with uncertainties generally <0.003 sr–1. Such an approach led to observations of short-term changes in AISA-retrievedRrsfrom repeated measurements over waters with bottom types of seagrass meadow, sand, and patch reef. Some of these changes are larger than twofold theRrsuncertainties from AISA retrievals, therefore representing statistically significant changes that can be well observed from airborne measurements. Through radiative transfer modelling, we demonstrated that short-termRrschanges within 1 hour resulted primarily from sediment resuspension, while tides played a relatively minor role due to the small variation in tidal heights. A sensitivity analysis indicated that althoughRrsgenerally increases with decreasing tide height but increasing suspended sediments, more changes were observed over sandy bottom than over seagrass. The case study suggests that repeated airborne measurements may be used to study short-term changes in shallow-water environments, and such a capacity may be enhanced with future geostationary satellite missions specifically designed to observe coastal ecosystems. [ABSTRACT FROM AUTHOR]