Intercomparison of smoke aerosol optical thickness derived from GOES 8 imager and ground-based Sun photometers

Using high temporal resolution GOES 8 imager data and radiative transfer calculations, smoke aerosol optical thickness (τ) is retrieved over selected sites in South America and Central America. The degradation of the signal response in the GOES 8 visible channel is estimated and the satellite-retrieved τ values are then compared against ground-based Sun photometer derived values. The satellite-retrieved values are in good agreement with ground-based τ for two sites in South America with mean linear correlation coefficients of 0.97. For Central America the mean correlation coefficient is 0.80. A single scattering albedo of 0.90 (at 0.67 μm) yields the best agreement between ground-based and satellite retrieved values and is consistent with previous studies. However, our results show that the retrieved optical thickness results are sensitive to single scattering albedo and surface reflectance. For example, a ±3.3% change in single scattering albedo (0.90±0.03) yields an uncertainty in τ of 10% for small optical thickness (τ = 0.5) and an uncertainty of about 25% for larger optical thickness values (τ = 1.5). Although the GOES 8 visible channel has undergone significant degradation in signal response since launch, smoke aerosol optical thickness can be estimated if proper procedures are used to account for this effect.