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The following are some of
the USGCRP's major accomplishments related to the Composition and Chemistry
of the Atmosphere during Fiscal Year 2000:
 New
observational and model results have shown that the chemistry and meteorology
of the stratosphere are influencing the dynamics of the troposphere, including
tropospheric temperatures. Thin layers in the troposphere appear to form
from the lateral and downward transport of air from the stratosphere and
the lofting of pollution into the middle and upper troposphere.
Long-term
studies of the polar vortices that trap air throughout the winter and
enhance ozone depletion show that, since the 1980s, there has been an
increase in the persistence of these patterns, with larger variations
in the Arctic than in the Antarctic.
Aircraft
measurements carried out as part of the Stratospheric Aerosol and Gas
Experiment (SAGE III) Ozone Loss and Validation Experiment (SOLVE) campaign
have provided new information about the formation of polar stratospheric
clouds and their effects on atmospheric chemistry in the Arctic region.
Detailed analyses of SOLVE data should reduce uncertainties about the
possibility of continuing Arctic ozone loss over the next decade and the
nature and timing of the expected long-term ozone recovery.
The
Indian Ocean Experiment (INDOEX) -- an international study of how air pollutants
are transported through the atmosphere and how they affect atmospheric
composition and solar radiation processes over the ocean -- is finding that
particles of soot produced in southern Asia can be a significant contributor
to surface warming in the Indian Ocean. These pollutants heat the lower
atmosphere directly by absorbing sunlight and indirectly by burning off
clouds and thus may have important consequences for the region's climate
and hydrologic cycle.
The
Pacific Exploratory Mission in the Tropics provided the first extensive
measurements of the hydroxyl radical (OH) oxidant in the tropical troposphere.
These measurements demonstrated that global model predictions of atmospheric
OH levels are basically correct. These model predictions have played a
critical role in environmental policy -- notably for the replacement of CFCs
by products that undergo oxidation by OH in the troposphere -- and their
verification represents a critical milestone for atmospheric chemistry.
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Focus Area
