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The GRAPE aerosol retrieval algorithm
1Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
2Space Science and Technology Department, Rutherford Appleton Laboratory, Chilton, Didcot, UK
*now at: Department of Medical Physics and Bioengineering, Christchurch Hospital, New Zealand
**now at: National Institute of Water and Atmospheric Research, Wellington, New Zealand
Abstract. The aerosol component of the Oxford-Rutherford Aerosol and Cloud (ORAC) combined cloud and aerosol retrieval scheme is described and the theoretical performance of the algorithm is analysed. ORAC is an optimal estimation retrieval scheme for deriving cloud and aerosol properties from measurements made by imaging satellite radiometers and, when applied to cloud free radiances, provides estimates of aerosol optical depth at a wavelength of 550 nm, aerosol effective radius and surface reflectance at 550 nm. The aerosol retrieval component of ORAC has several incarnations – this paper addresses the version which operates in conjunction with the cloud retrieval component of ORAC (described by Watts et al., 1998), as applied in producing the Global Retrieval of ATSR Cloud Parameters and Evaluation (GRAPE) data-set.
The algorithm is described in detail and its performance examined. This includes a discussion of errors resulting from the formulation of the forward model, sensitivity of the retrieval to the measurements and a priori constraints, and errors resulting from assumptions made about the atmospheric/surface state.
Discussion Paper (PDF, 960 KB) Interactive Discussion (Closed, 6 Comments)Final Revised Paper (AMT)
Citation: Thomas, G. E., Poulsen, C. A., Sayer, A. M., Marsh, S. H., Dean, S. M., Carboni, E., Siddans, R., Grainger, R. G., and Lawrence, B. N.: The GRAPE aerosol retrieval algorithm, Atmos. Meas. Tech. Discuss., 2, 981-1026, 2009. Bibtex EndNote Reference Manager
