Toward a minimal representation of aerosols in climate models

Description and evaluation in the Community Atmosphere Model CAM5

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, Sang Hun Park, R. Neale, C. Hannay, A. M.L. Ekman, P. Hess, N. Mahowald, W. Collins, M. J. Iacono, C. S. Bretherton & 2 others M. G. Flanner, D. Mitchell

Research output: Contribution to journalArticle

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Abstract

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.

Original languageEnglish
Pages (from-to)709-739
Number of pages31
JournalGeoscientific Model Development
Volume5
Issue number3
DOIs
Publication statusPublished - 2012 Dec 1

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Climate models
Climate Models
Aerosol
Aerosols
Atmosphere
climate modeling
aerosol
atmosphere
Evaluation
Model
sea salt
Salt
Community
evaluation
Module
Developing Countries
black carbon
Salts
Carbon black
optical property

All Science Journal Classification (ASJC) codes

  • Modelling and Simulation
  • Earth and Planetary Sciences(all)

Cite this

Liu, X. ; Easter, R. C. ; Ghan, S. J. ; Zaveri, R. ; Rasch, P. ; Shi, X. ; Lamarque, J. F. ; Gettelman, A. ; Morrison, H. ; Vitt, F. ; Conley, A. ; Park, Sang Hun ; Neale, R. ; Hannay, C. ; Ekman, A. M.L. ; Hess, P. ; Mahowald, N. ; Collins, W. ; Iacono, M. J. ; Bretherton, C. S. ; Flanner, M. G. ; Mitchell, D. / Toward a minimal representation of aerosols in climate models : Description and evaluation in the Community Atmosphere Model CAM5. In: Geoscientific Model Development. 2012 ; Vol. 5, No. 3. pp. 709-739.
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abstract = "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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Liu, X, Easter, RC, Ghan, SJ, Zaveri, R, Rasch, P, Shi, X, Lamarque, JF, Gettelman, A, Morrison, H, Vitt, F, Conley, A, Park, SH, Neale, R, Hannay, C, Ekman, AML, Hess, P, Mahowald, N, Collins, W, Iacono, MJ, Bretherton, CS, Flanner, MG & Mitchell, D 2012, 'Toward a minimal representation of aerosols in climate models: Description and evaluation in the Community Atmosphere Model CAM5', Geoscientific Model Development, vol. 5, no. 3, pp. 709-739. https://doi.org/10.5194/gmd-5-709-2012

Toward a minimal representation of aerosols in climate models : Description and evaluation in the Community Atmosphere Model CAM5. / Liu, X.; Easter, R. C.; Ghan, S. J.; Zaveri, R.; Rasch, P.; Shi, X.; Lamarque, J. F.; Gettelman, A.; Morrison, H.; Vitt, F.; Conley, A.; Park, Sang Hun; Neale, R.; Hannay, C.; Ekman, A. M.L.; Hess, P.; Mahowald, N.; Collins, W.; Iacono, M. J.; Bretherton, C. S.; Flanner, M. G.; Mitchell, D.

In: Geoscientific Model Development, Vol. 5, No. 3, 01.12.2012, p. 709-739.

Research output: Contribution to journalArticle

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T1 - Toward a minimal representation of aerosols in climate models

T2 - Description and evaluation in the Community Atmosphere Model CAM5

AU - Liu, X.

AU - Easter, R. C.

AU - Ghan, S. J.

AU - Zaveri, R.

AU - Rasch, P.

AU - Shi, X.

AU - Lamarque, J. F.

AU - Gettelman, A.

AU - Morrison, H.

AU - Vitt, F.

AU - Conley, A.

AU - Park, Sang Hun

AU - Neale, R.

AU - Hannay, C.

AU - Ekman, A. M.L.

AU - Hess, P.

AU - Mahowald, N.

AU - Collins, W.

AU - Iacono, M. J.

AU - Bretherton, C. S.

AU - Flanner, M. G.

AU - Mitchell, D.

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N2 - 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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