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| Titel |
Interactive chemistry in the Laboratoire de Météorologie Dynamique general circulation model: model description and impact analysis of biogenic hydrocarbons on tropospheric chemistry |
| VerfasserIn |
G. A. Folberth, D. A. Hauglustaine, J. Lathière, F. Brocheton |
| 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. 8 ; Nr. 6, no. 8 (2006-06-21), S.2273-2319 |
| Datensatznummer |
250003931
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| Publikation (Nr.) |
 copernicus.org/acp-6-2273-2006.pdf |
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| Zusammenfassung |
| We present a description and evaluation of LMDz-INCA, a global
three-dimensional chemistry-climate model, pertaining to its recently developed
NMHC version. In this substantially extended version of the model a
comprehensive representation of the photochemistry of non-methane hydrocarbons
(NMHC) and volatile organic compounds (VOC) from biogenic, anthropogenic, and
biomass-burning sources has been included. The tropospheric annual mean methane
(9.2 years) and methylchloroform (5.5 years) chemical lifetimes are well within
the range of previous modelling studies and are in excellent agreement with
estimates established by means of global observations. The model provides a
reasonable simulation of the horizontal and vertical distribution and seasonal
cycle of CO and key non-methane VOC, such as acetone, methanol, and
formaldehyde as compared to observational data from several ground stations and
aircraft campaigns. LMDz-INCA in the NMHC version reproduces tropospheric ozone
concentrations fairly well throughout most of the troposphere. The model is
applied in several sensitivity studies of the biosphere-atmosphere
photochemical feedback. The impact of surface emissions of isoprene, acetone,
and methanol is studied. These experiments show a substantial impact of
isoprene on tropospheric ozone and carbon monoxide concentrations revealing an
increase in surface O3 and CO levels of up to 30 ppbv and 60 ppbv,
respectively. Isoprene also appears to significantly impact the global OH
distribution resulting in a decrease of the global mean tropospheric OH
concentration by approximately 0.7×105 molecules cm-3 or
roughly 8% and an increase in the global mean tropospheric methane lifetime
by approximately seven months. A global mean ozone net radiative forcing due to
the isoprene induced increase in the tropospheric ozone burden of
0.09 W m-2 is found. The key role of isoprene photooxidation in the
global tropospheric redistribution of NOx is demonstrated. LMDz-INCA
calculates an increase of PAN surface mixing ratios ranging from 75 to 750 pptv
and 10 to 250 pptv during northern hemispheric summer and winter, respectively.
Acetone and methanol are found to play a significant role in the upper
troposphere/lower stratosphere (UT/LS) budget of peroxy radicals. Calculations
with LMDz-INCA show an increase in HOx concentrations region of 8 to
15% and 10 to 15% due to methanol and acetone biogenic surface emissions,
respectively. The model has been used to estimate the global tropospheric CO
budget. A global CO source of 3019 Tg CO yr-1 is estimated. This
source divides into a primary source of 1533 Tg CO yr-1 and secondary
source of 1489 Tg CO yr-1 deriving from VOC photooxidation. Global
VOC-to-CO conversion efficiencies of 90% for methane and between 20 and 45%
for individual VOC are calculated by LMDz-INCA. |
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