NASA Scientific and Technical Aerospace Reports

GEOS-CHEM global three-dimensional model of tropospheric chemistry and simulating the Pacific Exploratory Mission-West
(PEM-West B) aircraft mission in February-March 1994. The GEOS-CHEM model uses assimilated meteorological fields
from the NASA Goddard Earth Observing System (GEOS). It reproduces relatively well the main features of tropospheric
ozone, CO, and reactive nitrogen species observed in PEM-West B, including latitudinal and vertical gradients of the Asian
pollution outflow over the western Pacific although simulated concentrations of CO tend to be too low (possibly because
biogenic sources are underestimated). We use CO as a long-lived tracer to diagnose the processes contributing to the outflow.
The highest concentrations in the outflow are in the boundary layer (0-2 km), but the strongest outflow fluxes are in the lower
free troposphere (2-5 km) and reflect episodic lifting of pollution over central and eastern China ahead of eastward moving
cold fronts. This frontal lifting, followed by westerly transport in the lower free troposphere, is the principal process
responsible for export of both anthropogenic and biomass burning pollution from Asia. Anthropogenic emissions from Europe
and biomass burning emissions from Africa make also major contributions to the Asian outflow over the western Pacific;
European sources dominate in the lower troposphere north of 40 degrees N, while African sources are important in the upper
troposphere at low latitudes. For the period of PEM-West B (February-March) we estimate that fossil fuel combustion and
biomass burning make comparable contributions to the budgets of CO, ozone, and NO, in the Asian outflow. We find that 13%
of NO, emitted in Asia is exported as NO, or PAN, a smaller fraction than for the USA because of higher aerosol
concentrations that promote heterogeneous conversion of NOx to HNO3. Production and export of ozone from Asia in spring
is much greater than from the USA because of the higher photochemical activity.
Author
Asia; Spring (Season); Pacific Ocean; Atmospheric Chemistry; Atmospheric Models; Meteorological Parameters; Pacific
Islands
20040111411 Harvard Univ., Cambridge, MA, USA
Air Mass Factor Formulation for Spectroscopic Measurements from Satellites: Application to Formaldehyde
Retrievals from the Global Ozone Monitoring Experiment
Palmer, Paul I.; Jacob, Daniel J.; Chance, Kelly; Martin, Randall V.; Spurr, Robert J. D.; Kurosu, Thomas P.; Bey, Isabelle;
Yantosca, Robert; Fiore, Arlene; Li, Qinbin; Journal of Geophysical Research; January 2004; ISSN 0148-0227; Volume 106,
No. D13, pp. 14,539 - 14,440; In English; Original contains color illustrations
Contract(s)/Grant(s): NAG1-2307
Report No.(s): Paper-2000JD900772.; Copyright; Avail: Other Sources
We present a new formulation for the air mass factor (AMF) to convert slant column measurements of optically thin
atmospheric species from space into total vertical columns. Because of atmospheric scattering, the AMF depends on the
vertical distribution of the species. We formulate the AMF as the integral of the relative vertical distribution (shape factor) of
the species over the depth of the atmosphere, weighted by altitude-dependent coefficients (scattering weights) computed
independently from a radiative transfer model. The scattering weights are readily tabulated, and one can then obtain the AMF
for any observation scene by using shape factors from a three dimensional (3-D) atmospheric chemistry model for the period
of observation. This approach subsequently allows objective evaluation of the 3-D model with the observed vertical columns,
since the shape factor and the vertical column in the model represent two independent pieces of information. We demonstrate
the AMF method by using slant column measurements of formaldehyde at 346 nm from the Global Ozone Monitoring
Experiment satellite instrument over North America during July 1996. Shape factors are cumputed with the Global Earth
Observing System CHEMistry (GEOS-CHEM) global 3-D model and are checked for consistency with the few available
aircraft measurements. Scattering weights increase by an order of magnitude from the surface to the upper troposphere. The
AMFs are typically 20-40% less over continents than over the oceans and are approximately half the values calculated in the
absence of scattering. Model-induced errors in the AMF are estimated to be approximately 10%. The GEOS-CHEM model
captures 50% and 60% of the variances in the observed slant and vertical columns, respectively. Comparison of the simulated
and observed vertical columns allows assessment of model bias.
Author
Ozone; Spectroscopy; Three Dimensional Models; Air Masses; Formaldehyde; Atmospheric Chemistry
20040111550 Naval Postgraduate School, Monterey, CA
Naval Postgraduate School Research. Volume 14, Number 1, February 2004
Wash, Carlyle H.; Feb. 2004; 53 pp.; In English; Original contains color illustrations
Report No.(s): AD-A425586; No Copyright; Avail: CASI; A04, Hardcopy
This issue of Naval Postgraduate School Research focuses on meteorology. The school’s Department of Meteorology is
internationally recognized for its outstanding record of research and instruction. Perhaps less known is the important role the
155