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| Titel |
Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5 |
| VerfasserIn |
X. Liu, R. C. Easter, S. J. Ghan, R. Zaveri, P. Rasch, X. Shi, J.-F. Lamarque, A. Gettelman, H. Morrison, F. Vitt, A. Conley, S. Park, R. Neale, C. Hannay, A. M. L. Ekman, P. Hess, N. Mahowald, W. Collins, M. J. Iacono, C. S. Bretherton, M. G. Flanner, D. Mitchell |
| 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 ; 5, no. 3 ; Nr. 5, no. 3 (2012-05-21), S.709-739 |
| Datensatznummer |
250002613
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| Publikation (Nr.) |
 copernicus.org/gmd-5-709-2012.pdf |
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| Zusammenfassung |
A modal aerosol module (MAM) has been developed for the Community Atmosphere
Model version 5 (CAM5), the atmospheric component of the Community Earth
System Model version 1 (CESM1). MAM is capable of simulating the aerosol
size distribution and both internal and external mixing between aerosol
components, treating numerous complicated aerosol processes and aerosol
physical, chemical and optical properties in a physically-based manner. Two
MAM versions were developed: a more complete version with seven lognormal
modes (MAM7), and a version with three lognormal modes (MAM3) for the
purpose of long-term (decades to centuries) simulations. In this paper a
description and evaluation of the aerosol module and its two representations
are provided. Sensitivity of the aerosol lifecycle to simplifications in the
representation of aerosol is discussed.
Simulated sulfate and secondary organic aerosol (SOA) mass concentrations
are remarkably similar between MAM3 and MAM7. Differences in primary organic
matter (POM) and black carbon (BC) concentrations between MAM3 and MAM7 are
also small (mostly within 10%). The mineral dust global burden differs by
10% and sea salt burden by 30–40% between MAM3 and MAM7, mainly due to
the different size ranges for dust and sea salt modes and different standard
deviations of the log-normal size distribution for sea salt modes between
MAM3 and MAM7. The model is able to qualitatively capture the observed
geographical and temporal variations of aerosol mass and number
concentrations, size distributions, and aerosol optical properties. However,
there are noticeable biases; e.g., simulated BC concentrations are
significantly lower than measurements in the Arctic. There is a low bias in
modeled aerosol optical depth on the global scale, especially in the
developing countries. These biases in aerosol simulations clearly indicate
the need for improvements of aerosol processes (e.g., emission fluxes of
anthropogenic aerosols and precursor gases in developing countries, boundary
layer nucleation) and properties (e.g., primary aerosol emission size, POM
hygroscopicity). In addition, the critical role of cloud properties (e.g.,
liquid water content, cloud fraction) responsible for the wet scavenging of
aerosol is highlighted. |
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