Radiation, aerosols and clouds
The effect of aerosol particles on climate, although recognized, still needs to be quantified precisely. Aerosol particles interact directly with solar radiation through scattering and absorption processes. Scattering decreases the amount of global solar irradiance reaching the surface and increases its diffuse fraction. Absorption process also decreases downward solar radiation at the surface and also contributes to heat atmospheric layers containing aerosol particles. In this subproject we intend to evaluate the effect of urban (Sao Paulo) and biomass burning (in the Amazon region) aerosol particles on the solar radiation reaching the surface. In Sao Paulo, the main goal is to quantify the effect of aerosol particles on ultraviolet radiation. In the Amazon region, we intend to evaluate the consequences of surface radiation deficit on the turbulent sensible and latent heat and CO2 fluxes. Another task is to evaluate the contribution of diffuse radiation on CO2 flux. Comparing to direct radiation, diffuse solar radiation can penetrate more efficiently inside heterogeneous canopy, as in the tropical rainforest. Higher penetration efficiency can increase photosynthetic efficiency, since radiation can reach direct-radiation-shaded-leaves. Furthermore, since cloud cover is frequent in the Amazon region even during the dry season, another objective is to analyze the simultaneous effect of aerosol and clouds on solar radiation through radiative transfer calculations. Last, but not least, we also intend to analyze aerosol-cloud interactions in the lab, through controlled experiments.