科研之友
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摘要
The concept behind the shortcut idea is a close correlation between column broadband aerosol optical depth (BAOD) and aerosol optical depth at 500 nm (AOD500). The method uses only two input parameters: (a) the Bouguer broadband coefficient of column transparency for optical mass m = 2 (solar elevation about 30 degrees) and (b) integrated column precipitable water vapour which can be roughly estimated using surface water vapour pressure. In creating the method, a large database, including almost 20 000 complex, spectral and broadband direct solar beam observations at Toravere, Estonia, during all seasons of a 8-year period, 2002-2009, was used. The AOD500 observations were performed by the NASA project AERONET and the broadband direct beam ones by the Estonian Meteorological and Hydrological Institute. Analysis of this database revealed a high correlation between BAOD and AOD500 which enabled transition from broadband to spectral AOD. Almost 82% of the observations in the database belonged to lower turbidities when AOD500 %26lt; 0.2. The root mean square deviation (RMSD) for AOD500 prediction in this range was 0.022. For AOD500 = 0.2-0.4, the RMSD was 0.035, for 0.4-0.6, the RMSD was 0.042. Relative RMSD for these ranges was about 22%, 12%, and 9%, respectively. For AOD500 %26gt; 0.6, relative RMSD remained 9%. For comparison, the same database was used to test Gueymard%26apos;s broadband parameterization based on his SMARTS2 classic model. The last one, apparently due to problems with circumsolar radiation, slightly but systematically underestimated the AOD500. However, there was a close correlation between our shortcut results and Gueymard%26apos;s broadband parameterization.
- 出版日期2012
