Atmospheric Boundary Layer Experiment-2

Project Description
The ABLE missions have been designed specifically to study the rate of
exchange of material between the Earth's surface and its atmospheric
boundary layer, and the processes by which gases and aerosols are
moved between the boundary layer and the 'free' troposphere. These
expeditions are conducted in ecosystems of the world that are ... known to
exert a major influence on global atmospheric chemistry. In some
cases, these ecosystems are undergoing profound changes as a
consequence of natural processes and/or human impact.

The ABLE-2 project consisted of two expeditions: the first in the
Amazonian dry season (ABLE-2A, July-August 1985); and the second in
the wet season (ABLE-2B, April-May 1987). The ABLE-2 core research
data were gathered by NASA Electra aircraft flights that stretched
from Belem, at the mouth of the Amazon River, west to Tabatinga, on
the Brazil-Colombia border, from a base at Manaus in the heart of the
forest. These observations were supplemented by ground based chemical
and meteorological measurements in the dry forest, the Amazon
floodplain, and the tributary rivers through use of enclosures, an
instrumented tower in the jungle, a large tethered balloon, and
weather and ozonesondes.

This study showed air above the Amazon jungle to be extremely clean
during the wet season but deteroirated dramatically during the dry
season as the result of biomass burning, performed mostly at the edges
of the forest. Biomass burning is also a source of greenhouse gases
carbon dioxide and methane, as well as other pollutants (carbon
monoxide and oxides of nitrogen). Amazonian ozone deposition rates
were found to be 5 to 50 times higher than those previously measured
over pine forests and water surfaces. The Amazon River floodplain is
a globally significant source of methane, supplying about 12% of the
estimated worldwide total from all wetlands sources. Over Amazonia,
carbon monoxide is enhanced by factors ranging from 1.2 to 2.7 by
comparison with adjacent regions due to isoprene oxidation and biomass
burning. Over the rainforest individual convective storms transport
200 megatons of air per hour, of which 3 megatons is water vapor that
releases 100,000 megawatts of energy into the atmosphere through
condensation into rain.

The ABLE was a collaboration of U.S. and Brazilian scientists
sponsored by NASA and Instituto Nacional de Pesquisas Espaciais (INPE)
and supported by the Global Tropospheric Experiment (GTE) component of
the NASA Tropospheric Chemistry Program.

ABLE-2 data is also available on CD-ROM: