2. Methods and Materials
2.1 Study Area
Apalachicola Bay is a wide estuarine system located in the Florida panhandle and covers an area about 539 km2 (Figure 1). The bay is relatively shallow with an average depth of 3.0 m. It is one of the most productive natural systems in North America, and highly recognized by the state, federal and international organizations for its pristine water quality and unaffected estuarine habitats (ANERR, 2008). Apalachicola Bay was formed by the deltaic processes of the Apalachicola River, which is a relatively unpolluted alluvial system. The bay is surrounded by four barrier islands: St. Vincent Island, Little St. George Island, St. George Island and Dog Island. The water exchange between the relatively fresh bay and the saline Gulf waters occurs
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FLAASH removes aerosol from satellite image and corrects it for adjacency effect, however it does not remove the contribution of skylight, white-caps, and sun-glint. Therefore, AERONET based total radiance (Lt) was used to compare with satellite based surface radiance (Lu) rather than water-leaving radiance (Lw). Satellite derived surface reflectance (ρ) were converted to Lu using the following equation, Surface reflectance (ρ)= (L_u× F_0× Cos (θ))/(π × d^2 ) (3)
Where Lu = surface radiance (mWcm-2µm-1sr-1), F0 = Extraterrestrial solar irradiance (mWcm-2µm-1sr-1), θ is solar zenith angle, d is correction factor for Earth-Sun distance. 2.3.4 Statistical analysis
In the case of remotely-sensed data, the matchup comparisons between satellite-derived estimates and in situ measurements of turbidity were evaluated using statistical criteria, such as root mean square error (RMSE), Pearson’s correlation coefficient (r) and