A three-dimensional radiative heat transfer analysis of an arbitrary-shaped modeled cloud subjected to solar and sky irradiation has been performed. The Radiation Element Method by Ray Emission Model (REM2) was used for numerical simulation. Nongray, anisotropic scattering, absorbing, and emitting are taken into account in calculating the three-dimensional cloud. The modeled cloud is considered to be a low-level fair-weather cumulus in a tropical atmosphere. The cloud is modeled by unstructured mesh elements in order to investigate the curvature of cloud shape. Radiative cooling occurs in the thin layer below the cloud surface, and the thickness is approximately 20-40 m. Radiative cooling is enhanced at the swelled top of the cloud with a convex shape, which can cause a downward forcing and enhance the entrainment instability. On the other hand, radiative cooling close to the root of the swelled top is relatively weak. The solar heating does not affect the temperature change in the cloud compared with radiative heat transfer by longwave infrared radiation.
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