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| Titel |
Modelling of primary aerosols in the chemical transport model MOCAGE: development and evaluation of aerosol physical parameterizations |
| VerfasserIn |
B. Sič, L. El Amraoui, V. Marecal, B. Josse, J. Arteta, J. Guth, M. Joly, P. D. Hamer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 2 ; Nr. 8, no. 2 (2015-02-23), S.381-408 |
| Datensatznummer |
250116115
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| Publikation (Nr.) |
 copernicus.org/gmd-8-381-2015.pdf |
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| Zusammenfassung |
| This paper deals with recent improvements to the global chemical transport model of
Météo-France MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle) that consists of updates to different aerosol parameterizations. MOCAGE only
contains primary aerosol species: desert dust, sea salt, black carbon, organic carbon, and also
volcanic ash in the case of large volcanic eruptions.
We introduced important changes to the aerosol parameterization
concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and
wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant
source function is introduced for sea salt aerosols. Wet deposition is modified toward a more
physically realistic representation by introducing re-evaporation of falling rain and snowfall
scavenging and by changing the in-cloud scavenging scheme along with calculations of precipitation
cloud cover and rain properties. The sedimentation scheme update includes changes regarding the
stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI), the ground
(AERONET, EMEP), and a model inter-comparison project (AeroCom) are compared with MOCAGE simulations and
show that the introduced changes brought a significant improvement on aerosol representation,
properties and global distribution. Emitted quantities of desert dust and sea salt, as well their
lifetimes, moved closer towards values of AeroCom estimates and the multi-model average. When
comparing the model simulations with MODIS aerosol optical depth (AOD) observations over the
oceans, the updated model configuration shows a decrease in the modified normalized mean bias (MNMB; from 0.42 to 0.10) and
a better correlation (from 0.06 to 0.32) in terms of the geographical distribution and the
temporal variability. The updates corrected a strong positive MNMB in the sea salt representation
at high latitudes (from 0.65 to 0.16), and a negative MNMB in the desert dust representation in
the African dust outflow region (from −1.01 to −0.22). The updates in sedimentation produced
a modest difference; the MNMB with MODIS data from 0.10 in the updated configuration went to
0.11 in the updated configuration only without the sedimentation updates. Yet, the updates in
the emissions and the wet deposition made a stronger impact on the results; the MNMB was 0.27 and
0.21 in updated configurations only without emission, and only without wet deposition updates,
respectively. Also, the lifetime, the extent, and the strength of the episodic aerosol events
are better reproduced in the updated configuration. The wet deposition processes and the
differences between the various configurations that were tested greatly influence the
representation of the episodic events. However, wet deposition is not a continuous process; it has
a local and episodic signature and its representation depends strongly on the precipitation regime
in the model. |
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