An improved δ-Eddington approximation  

作　　者：QIU JinhuanInstitute of Atmospheric Physics , Chinese Academy of Sciences , Beijing 100029, China 

出　　处：《Chinese Science Bulletin》1999年第4期304-309,共6页

摘　　要：Based on an accuracy analysis of two-stream approximations, an improved δ-Eddington ap-proximation is developed. The approximation has much better accuracy than all exiting two-stream ap-proximations as the optical depth is less than unity. As the surface reflectance is zero and the opticaldepth is less than unity, errors in both transmission and reflection calculated by the present approxima-tion are more one time less than those by other two-stream approximations. In the case of aerosol opti-cal depth of【1, surface reflectance of 【 0.6, solar zenith angle of 【 78°and aerosol imaginary indexof 【 0.05, transmission and reflection errors calculated by the improved δ-Eddington approximationare generally less than 3.5% and 2.6%, respectively. The errors are over 41% and one times lessthan those by Eddington or δ-Eddington.Based on an accuracy analysis of two-stream approximations, an improved δ-Eddington approximation is developed. The approximation has much better accuracy than all exiting two-stream approximations as the optical depth is less than unity. As the surface reflectance is zero and the optical depth is less than unity, errors in both transmission and reflection calculated by the present approximation are more one time less than those by other two-stream approximations. In the case of aerosol optical depth of < 1, surface reflectance of < 0.6, solar zenith angle of < 78° and aerosol imaginary index of < 0. 05, transmission and reflection errors calculated by the improved δ-Eddington approximation are generally less than 3.5% and 2.6%, respectively. The errors are over 41% and one times less than those by Eddington or δ-Eddington.

关 键 词：radiation FLUX FRACTIONAL FACTOR of δ-function EDDINGTON approximation. 

分 类 号：P422[天文地球—大气科学及气象学]