FAST YET ACCURATE NET FLUX CALCULATION FOR REALISTIC ATMOSPHERES WITHVARIABLE AEROSOL LOADINGS

Using a perturbation approach computational results have been obtained for the net radiative flux at selected wavelengths in realistic aeros ol atmospheres. A simple interpolation scheme is presented that employ s three base model computations and allows one to obtain quasi-exact f lux results from precomputed perturbation data in a highly efficient m anner. It is shown how the adjoint transfer equation can be employed t o probe the atmosphere for certain radiative effects, i.e., in the pre sent case for the net radiative flux as a function of height. Results for three different aerosol profiles were obtained and compared with e xact calculations. Contour plots showing the relative error of the net flux underline that, over a wide range of aerosol perturbations (comp are 0.1 less than or similar to tau(c) less than or similar to 0.4 for continental-type aerosols) and for all solar zenith angles, perturbat ion theory produces relative errors below +/-0.25 %. Compared to commo nly used two-stream approximations, the perturbation approach not only offers the possibility to obtain the required model parameters off-li ne, that is, in a precomputed manner, but also enables one to study ra diative effects for thin and moderately thick optical media in the sen se of a functional sensitivity approach. Thus it can clearly be conclu ded that the methodological approach as presented in this study is sup erior to the commonly employed two-stream approximations for radiative transfer computations and in the future may be exploited to overcome the shortcomings of flux models.