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Modal Aerosol Module

MAM5 Overview

The Five-mode Modal Aerosol Model (MAM5) supersedes the MAM4 utilized in previous iterations of E3SM (E3SM-V1 and -V2). MAM5 introduces a fifth mode, specifically designed to represent stratospheric coarse mode aerosols, primarily originating from volcanic eruptions and DMS decomposition. This mode exclusively comprises sulfate aerosols, characterized by a smaller standard deviation (STD) value of 1.2. The STD value denotes the width of the aerosol mode, where a higher STD implies a greater gravitational settling effect (Wang et al., 2020;1 Liu et al., 20122). By setting the STD to 1.2, the simulated properties of volcanic aerosols align closely with observational findings (Mills et al., 2016).3 MAM5 represents a pioneering aerosol model, effectively segregating tropospheric and stratospheric aerosols (Ke et al., in preparation), thereby mitigating the risk of overestimating dust and sea salt aerosols within the stratosphere in previous MAM4 (Visioni et al., 2021).4 Volcanic eruptions derived from Neely and Schmidt (2016).5

MAM4 Overview

The representation of atmospheric aerosols and their roles in the Earth system by EAMv1/v2/v3 was inherited from the global aerosol-climate model EAMv0 and its four-mode modal aerosol module (MAM4), including Aitken, primary-carbon, accumulation, and coarse modes (Liu et al., 2016).6 It treats a combination of processes, controlling the evolution of aerosols that are either directly emitted or converted from precursor gases from a variety of natural and anthropogenic sources. The processes include transport (by grid-scale wind, subgrid turbulence, convection, and sedimentation), aerosol microphysics (i.e., particle nucleation, condensation/evaporation of trace gases, aging, and coagulation), cloud processing (i.e., aqueous chemistry, scavenging by hydrometeors, resuspension from evaporating hydrometeors, and wet deposition), and dry deposition. Aerosol species in the original MAM4 (Liu et al., 2016)6 include sulfate, primary organic aerosol (POA) or particulate organic matter (POM), secondary organic aerosol (SOA), black carbon (BC), sea salt, and mineral dust. As described by Wang et al. (2020),1 the enhanced MAM4 in EAMv1/v2 added marine organic aerosol (MOA) to all four modes (Burrows et al., 2022).7 In MAM4 of EAMv3, the Aitken mode has sulfate, sea salt, SOA and MOA; the primary-carbon mode has BC, POA and MOA; the accumulation and coarse modes include all seven species. Ammonium (NH4) and nitrate (NO3) aerosols are also explicitly treated in EAMv3 (Wu et al., 2022),8 as an optional feature for research, in which new species (NH4, NO3, Ca, CO3, Na, Cl) are introduced to the Aitken, accumulation and coarse modes. All aerosol species within each of the four individual modes the MAM4 is assumed to be internally mixed and represented by a single number concentration, while particles are externally mixed among the different modes.

Sea salt

In MAM4, sea salt aerosol is represented in the Aitken, accumulation, and coarse mode with particle emission size (diameter) ranges of 0.02-0.08, 0.08-1.0, and 1.0-10.0 μm, respectively. The emission flux of natural sea salt is first divided into 31 size bins, following the parameterization of Mårtensson et al. (2003)9 and Monahan et al. (1986),10 and then redistributed to the three MAM4 size modes.

Namelist parameters

MAM Namelist Parameters

  1. Hailong Wang, Richard C. Easter, Rudong Zhang, Po‐Lun Ma, Balwinder Singh, Kai Zhang, Dilip Ganguly, Philip J. Rasch, Susannah M. Burrows, Steven J. Ghan, Sijia Lou, Yun Qian, Yang Yang, Yan Feng, Mark Flanner, L. Ruby Leung, Xiaohong Liu, Manish Shrivastava, Jian Sun, Qi Tang, Shaocheng Xie, and Jin‐Ho Yoon. Aerosols in the E3SM Version 1: New Developments and Their Impacts on Radiative Forcing. Journal of Advances in Modeling Earth Systems, 12(1):e2019MS001851, January 2020. URL: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019MS001851 (visited on 2024-03-29), doi:10.1029/2019MS001851. ↩↩

  2. 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, and D. Mitchell. Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5. Geoscientific Model Development, 5(3):709–739, May 2012. URL: https://gmd.copernicus.org/articles/5/709/2012/ (visited on 2024-03-29), doi:10.5194/gmd-5-709-2012. ↩

  3. Michael J. Mills, Anja Schmidt, Richard Easter, Susan Solomon, Douglas E. Kinnison, Steven J. Ghan, Ryan R. Neely, Daniel R. Marsh, Andrew Conley, Charles G. Bardeen, and Andrew Gettelman. Global volcanic aerosol properties derived from emissions, 1990–2014, using CESM1(WACCM). Journal of Geophysical Research: Atmospheres, 121(5):2332–2348, March 2016. URL: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015JD024290 (visited on 2024-04-25), doi:10.1002/2015JD024290. ↩

  4. Daniele Visioni, Simone Tilmes, Charles Bardeen, Michael Mills, Douglas G. MacMartin, Ben Kravitz, and Jadwiga H. Richter. Limitations of assuming internal mixing between different aerosol species: a case study with sulfate geoengineering simulations. Atmospheric Chemistry and Physics, 22(3):1739–1756, February 2022. URL: https://acp.copernicus.org/articles/22/1739/2022/ (visited on 2024-04-25), doi:10.5194/acp-22-1739-2022. ↩

  5. R. R. Neely III and A. Schmidt. VolcanEESM: Global volcanic sulphur dioxide (SO2) emissions database from 1850 to present - Version 1.0. 2016. URL: https://catalogue.ceda.ac.uk/uuid/a8a7e52b299a46c9b09d8e56b283d385 (visited on 2024-04-25), doi:10.5285/76EBDC0B-0EED-4F70-B89E-55E606BCD568. ↩

  6. X. Liu, P.-L. Ma, H. Wang, S. Tilmes, B. Singh, R. C. Easter, S. J. Ghan, and P. J. Rasch. Description and evaluation of a new four-mode version of the Modal Aerosol Module (MAM4) within version 5.3 of the Community Atmosphere Model. Geoscientific Model Development, 9(2):505–522, February 2016. URL: https://gmd.copernicus.org/articles/9/505/2016/ (visited on 2024-03-29), doi:10.5194/gmd-9-505-2016. ↩↩

  7. Susannah M. Burrows, Richard C. Easter, Xiaohong Liu, Po-Lun Ma, Hailong Wang, Scott M. Elliott, Balwinder Singh, Kai Zhang, and Philip J. Rasch. OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) sea spray organic aerosol emissions – implementation in a global climate model and impacts on clouds. Atmospheric Chemistry and Physics, 22(8):5223–5251, April 2022. URL: https://acp.copernicus.org/articles/22/5223/2022/ (visited on 2024-03-29), doi:10.5194/acp-22-5223-2022. ↩

  8. Mingxuan Wu, Hailong Wang, Richard C. Easter, Zheng Lu, Xiaohong Liu, Balwinder Singh, Po‐Lun Ma, Qi Tang, Rahul A. Zaveri, Ziming Ke, Rudong Zhang, Louisa K. Emmons, Simone Tilmes, Jack E. Dibb, Xue Zheng, Shaocheng Xie, and L. Ruby Leung. Development and Evaluation of E3SM‐MOSAIC: Spatial Distributions and Radiative Effects of Nitrate Aerosol. Journal of Advances in Modeling Earth Systems, 14(11):e2022MS003157, November 2022. URL: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022MS003157 (visited on 2024-03-29), doi:10.1029/2022MS003157. ↩

  9. E. M. Mårtensson, E. D. Nilsson, G. De Leeuw, L. H. Cohen, and H.‐C. Hansson. Laboratory simulations and parameterization of the primary marine aerosol production. Journal of Geophysical Research: Atmospheres, 108(D9):2002JD002263, May 2003. URL: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2002JD002263 (visited on 2024-03-29), doi:10.1029/2002JD002263. ↩

  10. E. C. Monahan, D. E. Spiel, and K. L. Davidson. A Model of Marine Aerosol Generation Via Whitecaps and Wave Disruption. In Edward C. Monahan and Gearóid Mac Niocaill, editors, Oceanic Whitecaps: And Their Role in Air-Sea Exchange Processes, pages 167–174. Springer Netherlands, Dordrecht, 1986. URL: https://doi.org/10.1007/978-94-009-4668-2_16 (visited on 2024-03-29), doi:10.1007/978-94-009-4668-2_16. ↩