Aerosol particles in Amazonia: Their composition, role in the radiation balance, cloud formation, and nutrient cycles

Abstract

The atmosphere above tropical forests plays a very active part in the biogeochemical cycles that are critically important for the processes that maintain the ecosystem, including processes involving the vegetation, soil, hydrology, and atmospheric composition. Aerosol particles control key ingredients of the climatic and ecological environment in Amazonia. The radiative balance is strongly influenced by the direct and indirect radiative forcing of aerosol particles. Nutrient cycling is partially controlled by dry and wet deposition of key plant nutrients. It was observed that the aerosol particles that act as cloud condensation nuclei influence cloud formation and dynamics, having the potential to change precipitation regimes over Amazonia. The 10-year-long record of aerosol optical thickness measurements in Amazonia shows a strongly negative radiative forcing of -37 W m-2 averaged over 7 years of dry season measurements in Alta Floresta. There is a strong influence of biomass-burning aerosols on the cloud microphysical properties during the dry season. The connections between the amount of aerosol particles and carbon uptake trough photosynthesis highlighted the close connection between forest natural processes and the aerosol loading in the atmosphere. Climate change combined with socioeconomic drivers could alter significantly the emission of trace gases, aerosols, and water vapor fluxes from the forest to the atmosphere. It is a vital task to quickly reduce Amazonian deforestation rates, and to implement solid and long-term conservation policies in Amazonia. © Copyright 2009 by the American Geophysical Union.