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| Titel |
Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature) |
| VerfasserIn |
A. Guenther, T. Karl, P. Harley, C. Wiedinmyer, P. I. Palmer, C. Geron |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 11 ; Nr. 6, no. 11 (2006-08-02), S.3181-3210 |
| Datensatznummer |
250004048
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| Publikation (Nr.) |
 copernicus.org/acp-6-3181-2006.pdf |
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| Zusammenfassung |
| Reactive gases and aerosols are produced by terrestrial ecosystems,
processed within plant canopies, and can then be emitted into the
above-canopy atmosphere. Estimates of the above-canopy fluxes are needed for
quantitative earth system studies and assessments of past, present and
future air quality and climate. The Model of Emissions of Gases and Aerosols
from Nature (MEGAN) is described and used to quantify net terrestrial
biosphere emission of isoprene into the atmosphere. MEGAN is designed for
both global and regional emission modeling and has global coverage with
~1 km2 spatial resolution. Field and laboratory investigations of
the processes controlling isoprene emission are described and data available
for model development and evaluation are summarized. The factors controlling
isoprene emissions include biological, physical and chemical driving
variables. MEGAN driving variables are derived from models and satellite and
ground observations. Tropical broadleaf trees contribute almost half of the
estimated global annual isoprene emission due to their relatively high
emission factors and because they are often exposed to conditions that are
conducive for isoprene emission. The remaining flux is primarily from shrubs
which have a widespread distribution. The annual global isoprene emission
estimated with MEGAN ranges from about 500 to 750 Tg isoprene (440 to 660 Tg
carbon) depending on the driving variables which include temperature, solar
radiation, Leaf Area Index, and plant functional type. The global annual
isoprene emission estimated using the standard driving variables is ~600 Tg
isoprene. Differences in driving variables result in emission
estimates that differ by more than a factor of three for specific times and
locations. It is difficult to evaluate isoprene emission estimates using the
concentration distributions simulated using chemistry and transport models,
due to the substantial uncertainties in other model components, but at least
some global models produce reasonable results when using isoprene emission
distributions similar to MEGAN estimates. In addition, comparison with
isoprene emissions estimated from satellite formaldehyde observations
indicates reasonable agreement. The sensitivity of isoprene emissions to
earth system changes (e.g., climate and land-use) demonstrates the potential
for large future changes in emissions. Using temperature distributions
simulated by global climate models for year 2100, MEGAN estimates that
isoprene emissions increase by more than a factor of two. This is
considerably greater than previous estimates and additional observations are
needed to evaluate and improve the methods used to predict future isoprene
emissions. |
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