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GOES 8 retrieval of dust aerosol optical thickness over the Atlantic Ocean during PRIDE
Department of Atmospheric Sciences, University of Alabama in Huntsville, Huntsville, Alabama, USA
Department of Atmospheric Sciences, University of Alabama in Huntsville, Huntsville, Alabama, USA
Atmospheric Propagation Branch, SPAWAR System Center, San Diego, California, USA
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA
Biospheric Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
SRI International, Menlo Park, California, USA
NASA Ames Research Center, Moffett Field, California, USA
Climate Prediction Center, National Centers for Environmental Prediction, Washington, D. C., USA
Using 30 days of half-hourly, high temporal resolution GOES 8 imager data and radiative transfer calculations, dust aerosol optical thickness (AOT) was retrieved over the Atlantic Ocean (14°N ∼ 26°N, 73°W–63°W) during the Puerto Rico Dust Experiment (PRIDE). Dust aerosol size distributions and complex index of refraction inferred from ground-based measurements (1.53–0.0015i at 0.55 μm), which were used in Mie calculations and a plane-parallel discrete ordinate radiative transfer model (DISORT) to compute look up tables for AOT retrievals. Using a combination of spectral, spatial, and temporal tests, a dust detection algorithm was developed from the GOES 8 imager data. The degradation of the signal response relative to the prelaunched calibration of the GOES 8 visible channel was 39% in July 2000 and the GOES 8 AOT detection limit was estimated to be 0.04 in AOT (0.67 μm). The satellite-retrieved AOT were then compared with AOT values derived from ground-based Sun photometer (SP) sites. The comparison showed that GOES 8 retrieved AOT are in good agreement with the SP derived values, with linear correlation coefficient of 0.91 and 0.80 for the two sites. The GOES 8 monthly mean 0.67 μm AOT (0.19 ± 0.13, 0.22 ± 0.12) over the two SP sites matched the monthly mean SP AOT values (0.23 ± 0.13, 0.22 ± 0.10). The linear correlation between the GOES 8 retrieved AOT and the aircraft derived values from particle probe data and airborne Sun photometer AATS-6 measurements were 0.88 and 0.83, respectively. Besides the uncertainties from the nonspherical effect of dust aerosols, sensitivity studies showed that the uncertainties (Δτ) of the GOES 8 retrieved AOT values were mainly from the uncertainties due to the imaginary part of refractive index (Δτ = ±0.05) and surface reflectance [Δτ = ±(0.02 ∼ 0.04)]. This paper demonstrates the application of geostationary satellites to detect and retrieve dust AOT even at low to moderate AOTs. The GOES 8 imager with high temporal resolutions also captures aerosol diurnal variation in this study that can further reduce the uncertainties in the current aerosol forcing estimations caused by the high temporal variations of AOT, thereby playing a complementary role with global AOT retrievals from polar orbiting satellites.
Received 29 April 2002; accepted 17 December 2002; published 31 July 2003.
Citation: (2003), GOES 8 retrieval of dust aerosol optical thickness over the Atlantic Ocean during PRIDE, J. Geophys. Res., 108(D19), 8595, doi:10.1029/2002JD002494.
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