NASA Scientific and Technical Aerospace Reports

10-30 ppb, which could reflect a combination of excessive OH (a 20% decrease in model OH could be accommodated by the
methylchloroform constraint) and an underestimate of CO sources (particularly biogenic). The model underestimates observed
acetone concentrations over the South Pacific in fall by a factor of 3; a missing source from the ocean may be implicated.
Author
Meteorological Parameters; Troposphere; Three Dimensional Models; Atmospheric Chemistry
20040111405 Harvard Univ., Cambridge, MA, USA
Constraints Pb-210 and Be-7 on Wet Deposition and Transport in a Global Three-Dimensional Chemical Tracer Model
Driven by Assimilated Meteorological Fields
Liu, Hong-Yu; Jacob, Daniel J.; Bey, Isabelle; Yantosca, Robert M.; Journal of Geophysical Research; June 16, 2001; ISSN
0148-0227; Volume 106, No. D11, pp. 12109-12128; In English; Original contains color and black and white illustrations
Contract(s)/Grant(s): NAG1-2307
Report No.(s): Paper 2000JD900839; Copyright; Avail: Other Sources
The atmospheric distributions of the aerosol tracers Pb-210 and Be-7 are simulated with a global three-dimensional model
driven by assimilated meteorological observations for 1991-1996 from the NASA Goddard Earth Observing System (GEOSl).
The combination of terrigenic Pb-210 and cosmogenic Be-7 provides a sensitive test of wet deposition and vertical transport
in the model. Our simulation of moist transport and removal includes scavenging in wet convective updrafts (40% scavenging
efficiency per kilometer of updraft), midlevel entrainment and detrainment, first-order rainout and washout from both
convective anvils and large-scale precipitation, and cirrus precipitation. Observations from surface sites in specific years are
compared to model results for the corresponding meteorological years, and observations from aircraft missions over the Pacific
are compared to model results for the days of the flights. Initial simulation of Be-7 showed that cross-tropopause transport in
the GEOSl meteorological fields is too fast by a factor of 3-4. We adjusted the stratospheric Be-7 source to correct the
tropospheric simulation. Including this correction, we find that the model gives a good simulation of observed Pb-210 and
Be-7 concentrations and deposition fluxes at surface sites worldwide, with no significant global bias and with significant
success in reproducing the observed latitudinal and seasonal distributions. We achieve several improvements over previous
models; in particular, we reproduce the observed Be-7 minimum in the tropics and show that its simulation is sensitive to
rainout from convective anvils. Comparisons with aircraft observations up to 12-km altitude suggest that cirrus precipitation
could be important for explaining the low concentrations in the middle and upper troposphere.
Author
Lead Isotopes; Beryllium 7; Deposition; Meteorological Parameters; Three Dimensional Models; Transport Theory
20040111416 Harvard Univ., Cambridge, MA, USA
Mapping Isoprene Emissions over North America using Formaldehyde Column Observations from Space
Palmer, Paul I.; Jacob, Daniel J.; Fiore, Arlene M.; Martin, Randall V.; Chance, Kelly; Kurosu, Thomas P.; Journal of
Geophysical Research; January 2004; Volume 108, No. D6, pp. 2-1 - 2-9; In English
Contract(s)/Grant(s): NAG1-2307; Copyright; Avail: Other Sources
I] We present a methodology for deriving emissions of volatile organic compounds (VOC) using space-based column
observations of formaldehyde (HCHO) and apply it to data from the Global Ozone Monitoring Experiment (GOME) satellite
instrument over North America during July 1996. The HCHO column is related to local VOC emissions, with a spatial
smearing that increases with the VOC lifetime. lsoprene is the dominant HCHO precursor over North America in summer, and
its lifetime (approx. = 1 hour) is sufficiently short that the smearing can be neglected. We use the Goddard Earth Observing
System global 3-D model of tropospheric chemistry (GEOS-CHEM) to derive the relationship between isoprene emissions and
HCHO columns over North America and use these relationships to convert the GOME HCHO columns to isoprene emissions.
We also use the GEOS-CHEM model as an intermediary to validate the GOME HCHO column measurements by comparison
with in situ observations. The GEOS-CHEM model including the Global Emissions Inventory Activity (GEIA) isoprene
emission inventory provides a good simulation of both the GOME data (r(sup 2) = 0.69, n = 756, bias = +l1 %) and the in
situ summertime HCHO measurements over North America (r(sup 2) = 0.47, n = 10, bias = -3%). The GOME observations
show high values over regions of known high isoprene emissions and a day-to-day variability that is consistent with the
temperature dependence of isoprene emission. Isoprene emissions inferred from the GOME data are 20% less than GEIA on
average over North America and twice those from the US.EPABiogenic Emissions Inventory System (BEIS2) inventory.
The GOME isoprene inventory when implemented in the GEOS-CHEM model provides a better simulation of the HCHO in
situ measurements thaneitherGEIAorBEIS2 (r(sup 2) = 0.71,n= 10, bias = -10 %).
Author
Emission; Formaldehyde; Volatile Organic Compounds; In Situ Measurement; Atmospheric Chemistry
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