83rd Annual

Tuesday, 11 February 2003
Estimation of dust aerosol optical thickness and its shortwave radiative forcing from GOES8 imager
Jun Wang, University of Alabama, Huntsville, AL; and S. A. Christopher
Poster PDF (607.8 kB)

Satellite remote sensing plays a very important role in monitoring the geographic distributions of aerosols and the validation of numerical models.  Using GOES8 imager data and radiative model calculations, this paper demonstrated the retrieval of dust aerosol optical thickness (AOT) and the estimation of its shortwave aerosol forcing (SWARF) during the Puerto Rico Dust experiment (PRIDE) period (June 28 -July 24, 2000).  Dust aerosol size distributions and complex index of refraction inferred from ground-based measurements (1.53 – 0.0015i at 0.55mm), were used in Mie calculations and a plane-parallel Discrete Ordinate Radiative Transfer Model (DISORT) to compute look up tables for AOT retrievals.  The comparison showed that GOES-8 retrieved AOT are in good agreement with the Sun Photometer derived values, with linear correlation coefficient of 0.91 and 0.80 for the two AERONET sites.  The linear correlation between the GOES-8 retrieved AOT and the aircraft derived values from particle probe data and airborne sunphotometer AATS-6 measurements were 0.88 and 0.83 respectively.  GOES8 retrievals are then used in a four-stream radiative transfer model to calculate the SWARF.  Results show that the calculated direct, diffuse and total DSWI are in excellent agreement with the corresponding pyranometer values with biases of 1.8%, -3.3% and 0.5% respectively. This is well within the measurement (1.3%) and model uncertainties (5%).  The monthly mean AOT values during PRIDE are 0.26 ± 0.13, and the corresponding daytime monthly mean SWARF values are –12.34 ± 9.62 Wm-2 at TOA and  –18.13 ± 15.81 Wm-2 at the surface respectively. The algorithms and methods developed in this research demonstrate the potential of using geostationary satellite data to derive AOT and SWARF values over ocean.  


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