The cloud effect on the surface radiation budget at São Paulo Megacity

Abstract

Clouds have important role on the climate. They participate in the hydrological cycle and interact significantly both with the solar and the thermal radiation. In the solar spectrum, clouds can scatter and absorb solar radiation, while in the thermal infrared they absorb the radiation emitted by the surface and emit radiation back to the surface. The 3D non-homogeneous structure of clouds generates complex effects not easily represented in weather and climate models. For instance, the scattering of solar radiation when the solar disc is not blocked can enhance the amount of solar radiation reaching the surface. This results in a differential heating of the surface which affects the further development of the cloud field. Neglecting 3D radiative effects can generate large bias and evaluating them is a current scientific topic both in the solar and thermal spectral regions. Thus, cloud-radiation interactions are still large source of uncertainty and pose challenges in the numerical modeling of the climate system. In order to help understand such complex interactions, this research project aims to calculate the surface radiation budget at São Paulo city and evaluate the cloud effect on the four components of this budget, including modeling the 3D effect. In order to accomplish the goals, the four components of the surface radiation budget will be continuously monitored at high temporal resolution. Also, retrievals of cloud properties necessary to estimate their radiative effect will be performed, such as cloud optical thickness, effective radius, liquid or ice water path and cloud base height. At the end, we expect to provide a better characterization of cloud optical and physical properties in São Paulo city and a better understanding on its 3D radiative effect on the surface radiation budget and its importance to the regional climate. The results can be used to validate or improve satellite retrievals and numerical model simulations as well as to help evaluate the potential of using solar energy in the São Paulo Metropolitan Area. (AU)