Parcel Model Simulations of Aerosol-Cloud Microphysics Interactions over the Amazon
Abstract
Over tropical regions, such as the Amazon, biomass burning is a major source of aerosols that serve as cloud condensation nuclei (CCN). Changes in the cloud microphysics in association with smoke aerosols were first assessed as a possibility via modeling studies or satellite retrievals, and later verified by means of in-situ measurements. In particular, changes in the CCN field influence precipitation development in Amazon clouds, with significant suppression of warm rain processes, in agreement with previous satellite and radar studies. Nevertheless, there are still many questions regarding the formation of precipitation in the Amazon clouds that cannot be answered from the in-situ data alone: What is the role of the giant cloud condensation nuclei (GCCN) found in the different environments? How different updraft velocities influence precipitation development? How changes in the environmental humidity may influence the cloud life cycle? In this paper, we use a parcel model to simulate the development of warm rain in different aerosol regimes, from very clean to extremely polluted, as well as to explore sensitivities regarding the presence of giant CCN, the strength of the updraft velocities, and the availability of moisture at the sub-cloud layer. We found that the presence of GCCN and the control exerted by the low-level moisture over the warm rain height appear to be of comparable importance to CCN concentrationimportant to the change in rain characteristics in the transition from the dry to wet seasons over the Amazon.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFM.B43D..06C
- Keywords:
-
- 0305 Aerosols and particles (0345;
- 4801);
- 0320 Cloud physics and chemistry