Algorithm for retrieval of aerosol optical properties over the ocean from the Geostationary Ocean Color Imager |
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Authors: | Jaehwa Lee Jhoon Kim Chul H Song Yu-Hwan Ahn |
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Affiliation: | a Institute of Earth, Astronomy, and Atmosphere, Brain Korea 21 Program, Department of Atmospheric Sciences, Yonsei University, Seoul, Republic of Korea b Department of Environmental Engineering, GIST, Gwangju, Republic of Korea c Ocean Satellite Research Group, Korea Ocean Research and Development Institute, Ansan, Republic of Korea d Aerosol and Cloud Group, NASA JPL, Pasadena, and JIFRESSE, UCLA, L.A., CA, USA e National Institute of Environmental Research, Inchon, Korea |
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Abstract: | An aerosol retrieval algorithm for the first Geostationary Ocean Color Imager (GOCI) to be launched in March 2010 onboard the Communication, Ocean, and Meteorological Satellite (COMS) is presented. The algorithm retrieves aerosol optical depth (AOD), fine-mode fraction (FMF), and aerosol type in 500 m × 500 m resolution. All the products are retrieved over clear water which is defined by surface reflectance ratio between 640 nm and 860 nm (SRR) less or equal to 2.5, while only AOD is retrieved over turbid water (SRR > 2.5) due to high surface reflectance. To develop optimized algorithm for the target area of GOCI, optical properties of aerosol are analyzed from extensive observation of AERONET sunphotometers to generate lookup table. Surface reflectance of turbid water is determined from 30-day composite of Rayleigh- and gas corrected reflectance. By applying the present algorithm to MODIS top-of-the atmosphere reflectance, three different aerosol cases dominated by anthropogenic aerosol contains black carbon (BC), dust, and non-absorbing aerosol are analyzed to test the algorithm. The algorithm retrieves AOD, and size information together with aerosol type which are consistent with results inferred by RGB image in a qualitative way. The comparison of the retrieved AOD with those of MODIS collection 5 and AERONET sunphotometer observations shows reliable results. Especially, the application of turbid water algorithm significantly increases the accuracy in retrieving AOD at Anmyon station. The sensitivity study between MODIS and GOCI instruments in terms of relative sensitivity and scattering angle shows promising applicability of the present algorithm to future GOCI measurements. |
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Keywords: | Remote sensing Algorithm Aerosol optical depth Fine-mode fraction Aerosol type Geostationary |
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