Global Tropospheric Experiment

Project Description
Scientific Objectives:
This program will study the
-biological sources of atmospheric chemicals
-global distribution and long-range transport of chemical species
-reactions in the troposphere that lead to the conversion, redistribution, and
removal of atmospheric chemicals
Project Description:
The National Academy of Sciences in 1984 recommended initiation of a Global
Tropospheric Chemistry Program (GTCP), in recognition of the central role of
tropospheric chemistry in global change. The resources required are
distributed among several federal agencies, scores of universities, and a
variety of scientific disciplines-- including atmospheric science, biology,
land processes, and oceanography. NASA's contribution to the GTCP is the
Global Tropospheric Experiment (GTE), which utilizes large, extensively
instrumented aircraft, along with satellite observations of meteorology, land
use, and atmospheric chemical species to aid in experiment design and in the
scientific analysis of results obtained from aircraft and ground-based
measurements.
The first series of projects carried out under the GTE was the Chemical
Instrumentation Test and Evaluation (CITE) projects which exposed instruments
aboard aircraft to a wide range of conditions in both polluted and and
clean-air settings. CITE-1 was conducted in 1983 and consisted of a
ground-based experiment at Wallops Island, Virginia and aircraft-based over
California, southwestern U.S. and the central Pacific Ocean. CITE-2 was
conducted in 1986 over California and the eastern Pacific, and CITE-3 was
conducted in 1989 over Wallops Island, Virginia and the tropical Atlantic off
the coast of Brazil. The advanced instruments validated by CITE have been used
to carry out GTE field measurements.
The initial field expeditions, the Atmospheric Boundary Layer Experiment (ABLE)
projects, were designed to probe the interactions between the biosphere and the
atmosphere. They measured the fluxes of gases between the surface and the
atmospheric boundary layer (the tropospheric layer in direct contact with the
surface) and the mixing of gases from the boundary layer into the 'free
troposphere' above. The ABLE-1 experiment was conducted in 1984 over the
tropical Atlantic from a base in Barbados; ABLE-2 was conducted in 1985 and
1987 over the Amazon region; ABLE-3 was conducted in 1988 and 1990 over Alaska
and northern Canada.
Future experiments scheduled for the early 1990's include: the Transport and
Chemistry in the Atlantic (TRACE-A) which will investigate the distribution of
atmospheric trace gases over the tropical Atlantic; also the Pacific
Exploratory Mission (PEM) which will study atmospheric chemistry over the
Pacific Basin.
Data Used and Produced:
GTE is primarily a aircraft-based program supplemented by ground-based
measurements. The aircraft include the NASA Convair-990 and the Electra.
Space Shuttle, Landsat, and the NOAA weather satellites are also being
utilized. Global observations from space will ultimately be the technique of
choice for mapping the distributions of reactive, spatially variable chemical
species. Aircraft measurements will eventually provide 'ground truth' for
satellite measurements and explore in detail the processes responsible for the
observed distributions.
The Public Archive of data collected on the NASA/GTE program consists of data
from the CITE-1 Wallops Intercomparison Test in 1983 through the Amazon
Boundary Layer Experiment (ABLE-2B) in 1987. These data are stored on various
media including IBM-PC compatible diskettes, VAX 9-track tapes, tabular paper
listings, plots, videos and other film products, as well as weather charts and
summaries.
1. CITE-1 data: species measurements of methane, ozone, aerosols, carbon
monoxide, nitric oxide, hydroxyl radical, hydrocarbons, non-methane
hydrocarbons, sea salt, and ultraviolet flux, along with wind, temperature, and
dew point.
2. CITE-2 data: species measurements of carbon monoxide, ozone, nitric oxide,
nitrogen dioxide, reactive nitrogen, nitric acid, and peroxyacetyl nitrate.
3. ABLE-1 data: species measurements of ozone, aerosols, carbon monoxide,
hydrocarbons, ammonia, and dimethyl sulfide.
4. ABLE-2A data: species measurements of sulfur gases, ozone, aerosols, nitric
oxide, nitrous oxide, carbon dioxide, carbon monoxide, methane, particulate
organic carbon, methylhalides, hydrocarbons, and halocarbons, along with
surface fluxes of heat and water vapor, water chemistry, and tower
meteorological measurements.
5. ABLE-2B data: species measurements of sulfur gases, ozone, aerosols, nitric
oxide, nitrous oxide, carbon dioxide, carbon monoxide, methane, hydrocarbons,
isoprene, radon 222, water vapor, peroxyacetyl nitrate, and organic acids,
along with eddy heat and moisture fluxes, temperature, wind, radiation,
rainfall, and water chemistry.
Project Archive Contact: EOSDIS Langley DAAC
NASA Langley Research Center
Mail Stop 157B
Hampton, VA 23681-0001
Phone: (804) 864-8656
FAX: (804) 864-8807
Email: userserv@eosweb.larc.nasa.gov
WWW Home Page: http://eosweb.larc.nasa.gov/
Project Manager Contact: James Hoell
NASA Langley Research Center
Mail Stop 483
Hampton, VA 23681-0001
Phone: (804) 864-5826
FAX: (804) 864-5841
Email: j.m.hoell@larc.nasa.gov
References:
Drewry, J. W., and D. W. Owen, 1989: Global Tropospheric Experiment Data
Archive Catalog, NASA Langley Research Center.
Global Tropospheric Experiment Brochure
WWW: http://www-gte.larc.nasa.gov/gte_hmpg.htm