chapter - Atmospheric and Oceanic Science

Background on other regional aspects: Land use change, aerosols and trace gases
effect. Others are more effective in terms of absorbing solar radiation thus heating
the atmosphere. But aerosols also impact the cloud formation and structure
since they act as cloud condensation nuclei. Soil dust can also influence the
regional climate through the wind erosion.
e) Trace gases. Vegetation emits Volatile Organic Compounds (VOC) that have a
great influence on atmospheric chemistry, hydrology and climate though the production
of tropospheric O3, production of organic aerosols, cloud condensation
nuclei and acid rain formation. Land use change may have a significant impact
of the emission of VOC's because of the associated changes in the vegetation.
10.2 Regional effects of biomass burning
Biomass burning is certainly the major source of atmospheric aerosols in
South America away from the main cities (Artaxo et al. 1990; Echalar et al. 1998).
Carbonaceous aerosols of many forms, besides their radiative forcing also cause
respiratory problems. The main sources are fossil fuel and biomass burning, and
oxidation of VOCs. Natural biogenic aerosols also exist in the atmosphere and are
formed from plant debris (cuticular waxes, leaf fragments, etc.) organic matter, and
microbial particles (bacteria, fungi, viruses, algae, pollen, spores, etc.) as discussed
in Artaxo et al. (2003). Representative measurements of the various organic carbon
species in aerosols and the differentiation between black and organic carbon still
require improvement but there has been substantial progress in estimating the
regional impact in South America. Substantial progress has been made in recent
years with regard to the emissions factors i.e. the amount of aerosol emitted per
amount of biomass burned based on controlled experiments (Procópio et al. 2004).
Modelling studies have indicated the potential impact of biomass burning on
the precipitation (Moreira et al. 2004). Several recent studies have indicated that the
prevailing atmospheric circulation transports a significant amount of aerosols from
the biomass burning areas in the tropical region to higher latitudes in South
America (Freitas et al 1996, 2004, 2005). Under certain meteorological conditions,
in general associated with the presence of a strong northerly low level jet along the
Andes or a strong low level north westerly flow, the aerosol plume, produced by
biomass burning in the southern Amazon, travels towards Paraguay, northern
Argentina and Southern/Southeastern Brazil.
Greenhouse gases are also emitted during fires. The main emissions are: CO2,
CO (a quarter of all sources), CH4 (5 to 10% of all sources), nitric oxide, ammonia,
NO and VOCs. Significant amounts of methyl chloride (CH3Cl) and methyl bromide
(CH3BR) are emitted, both of which react with stratospheric ozone. Many of
the nitrogen and carbon-containing compounds emitted are chemically reactive and
are precursors of tropospheric ozone, and the interannual trends and seasonal cycle
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