13. Radiative Forcing

Radiative transfer is very important for tropical/subtropical meteorology. The subtropical highs occupy a large part of the subtropics, the temperature does not change much here from 1 day to the next inspite of the fact that descending air is continually warmed up by the adiabatic descent. That warming is offset by radiative cooling. Accurate modeling of radiative cooling in the presence of lower tropospheric stratus and strato-cumulus is an important issue for the tropics. Dust and aerosols abound in Asia and Africa and well stretched into the Atlantic and their rates of warming/cooling by radiative effects are a central issue for the modeling of the monsoon and hurricanes. Immediately below the cloud base long wave radiative flux convergence often leads to a warming by the long wave radiative process. Those are also important modeling issues. The clear weather shallow startocumulus carry a field of long wave cloud top cooling that dictates the low temperatures of the base of the trade wind inversion that also needs understanding of cloud radiative transfer processes. Various regions of the troposphere of the tropics show radiative stabilization or destabilization that are important for the thermodynamical/dynamical interactions and require understanding of physical processes. The entire seat of diurnal change in the atmosphere relates to the zenith angle of the sun and the understanding of diurnal change requires a detailed interpretation of radiative transfer. The heat budget of the land surface carries the impacts of short and long wave radiation at the Earth’s surface. These are areas where a considerable amount of research is needed to fully understand the role of land surface on the atmospheric processed. Even the Sea Surface Temperatures show a diurnal variability of the order of 0.5 C/day, that too has important implications for tropical buoyancy and clouds. There are major tropical circulations such as the Hadley and East West circulations that require understanding and careful modeling of radiative convective thermal balances.