A Study of Monte Carlo Radiative Transfer Through Fractal Clouds

Introduction An understanding of radiation transport (RT) through The goal of this experiment is to simulate radiation clouds is fundamental to studies of the earth’s radiation budget and climate dynamics. The transmission through horizontally homogeneous clouds has been studied thoroughly using accurate, discreet ordinates radiative transfer models. However, the applicability of these results to general problems of global radiation budget is limited by the plane parallel assumption and the fact that real cloud fields show variability, both vertically and horizontally, on all size scales. To understand how radiation interacts with realistic clouds, we have used a Monte Carlo radiative transfer model to compute the details of the photon-cloud interaction on synthetic cloud fields. Synthetic cloud fields, generated by a cascade model, reproduce the scaling behavior, as well as the cloud variability observed and estimated from cloud satellite data. through clouds using a scaling field to reproduce the variability of the cloud optical thickness at small-scale length. The scaling fields are generated using cascade processes characterized by a stable distribution specified by two parameters: and (see Figure 1). A Monte Carlo model was used to compute the interaction (scattering and absorption) between photons and cloud droplets. The radiance and flux fields were obtained from two realizations of the cloud field, both having the same values and This experiment is meant to investigate two important questions: 1) To what extent are the scaling and statistical properties of the original scaling fields of the cloud optical depth preserved in the resultant radiation fields? and