Multiple-scaling methods for Monte Carlo simulations of radiative transfer in cloudy atmosphere

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• 作者：Zhen Wang^a ;   ; ^b ;   ; ^{intersharp@126.com} ; Shizhi Yang^a ;   ; ^b ; Yanli Qiao^a ;   ; ^b ; Shengcheng Cui^a ;   ; ^b ; Qiang Zhao^a ;   ; ^b
• 关键词：Multiple-scaling ; Monte Carlo ; Radiative transfer ; Cloud field
• 刊名：Journal of Quantitative Spectroscopy and Radiative Transfer
• 出版年：2011
• 出版时间：November 2011
• 年：2011
• 卷：112
• 期：16
• 页码：2619-2629
• 全文大小：1389 K

文摘

Two multiple-scaling methods for Monte Carlo simulations were derived from integral radiative transfer equation for calculating radiance in cloudy atmosphere accurately and rapidly. The first one is to truncate sharp forward peaks of phase functions for each order of scattering adaptively. The truncated functions for forward peaks are approximated as quadratic functions; only one prescribed parameter is used to set maximum truncation fraction for various phase functions. The second one is to increase extinction coefficients in optically thin regions for each order scattering adaptively, which could enhance the collision chance adaptively in the regions where samples are rare. Several one-dimensional and three-dimensional cloud fields were selected to validate the methods. The numerical results demonstrate that the bias errors were below 0.2 % for almost all directions except for glory direction (less than 0.4 % ) and the higher numerical efficiency could be achieved when quadratic functions were used. The second method could decrease radiance noise to 0.60 % for cumulus and accelerate convergence in optically thin regions. In general, the main advantage of the proposed methods is that we could modify the atmospheric optical quantities adaptively for each order of scattering and sample important contribution according to the specific atmospheric conditions.