Spectral aerosol optical depth prediction by some broadband models. Validation with AERONET observations

A comprehensive investigation on the performance of aerosol optical depth at 500 nm (AOD500) predictions using broadband physical and statistical models is detailed here. Seven simple models and one more complicated model were selected. A special database with more than 26 000 broadband (direct solar beam) and spectral (AODλ) instantaneous observations at clear solar disc during 10 years (2002-2011) at Toravere (Estonia) was compiled for the intercomparison. The database allows analysing the variability and climatological behaviour of several column parameters: coefficient of broadband transparency, precipitable water, AOD500, and the Angstrom wavelength exponent (α). A statistical AOD500 model is finally recommended. It uses only two input parameters: coefficient of column broadband transparency and precipitable water. Two models from the set enabled variation of Angstrom α. However, consideration of a priori known instantaneous α values did not improve predictions.