AN APPROXIMATE EXPRESSION OF THE SKY RADIANCE IN ALMUCANTAR AND ITS APPLICATION

An approximate expression of the sky radiance in almucantar is confirmed in this paper. Under the conditions with molecular optical depth<0.3, aerosol (or cloud) optical depth<0.6. solar zenith angle< 75° and scattering angle<30°, the errors of the sky radiance and the aerosol phase function computed from the expression are respectively less than 8 % and 10 %, but the phase functions computed from Box-Deepak formula and single-scattering formula can be 84 % and 260 % more than the exact value, respectively. Furthermore, by use of the expression we have inferred the volume scattering functions of 1°≤θ≤30° for retrieving aerosol size distribution wath the conclusion that the distribution information in the range of 0.1<r<1500μm can be accurately obtained from the scattering channels of 1°≤θ≤30°.