Title: High Free-Tropospheric Aitken-Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large-Eddy Simulations of Precipitating Stratocumulus

Abstract

A new Aitken mode aerosol microphysics scheme is developed for a large eddy simulation model in order to better investigate cloud-aerosol interactions in the marine boundary layer and to study the Aitken buffering hypothesis of McCoy et al. (2021), https://doi.org/10.1029/2020jd033529. This scheme extends the single-mode two-moment prognostic aerosol scheme of Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. Seven prognostic variables represent accumulation and Aitken log-normal aerosol modes in air and droplets as well as 3 gas species. Scavenging of interstitial and other unactivated aerosol by cloud and rain drops are treated using the scheme described in Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. The scheme includes coagulation of unactivated aerosol and a simple chemistry model with gas phase H₂SO₄, SO₂, and DMS as prognostic variables to capture basic influences of sulfur chemistry on the model aerosols. Nucleation of H₂SO₄ aerosol particles from gas-phase H₂SO₄ is neglected. A deep, precipitating stratocumulus case (VAMOS Ocean Cloud Atmosphere Land Study RF06) is used to test the new scheme. The presence of the Aitken mode aerosol increases the cloud droplet concentration through activation of the larger Aitken particles and delays the creation of an ultraclean, strongly precipitating cumulus state. Scavenging of unactivated accumulation and Aitken particles by cloudmore » and precipitation droplets accelerates the collapse. Increasing either the above-inversion Aitken concentration or the surface Aitken flux increases the Aitken population in the boundary layer and prevents the transition to an ultraclean state.« less

Authors:

Wyant, Matthew C.  ^[1];

• Search DOE PAGES for author "Wyant, Matthew C."
• Search DOE PAGES for ORCID "0000-0002-4507-1684"

Bretherton, Christopher S.  ^[2];

• Search DOE PAGES for author "Bretherton, Christopher S."
• Search DOE PAGES for ORCID "0000-0002-6712-8856"

Wood, Robert  ^[1];

• Search DOE PAGES for author "Wood, Robert"
• Search DOE PAGES for ORCID "0000-0002-1401-3828"

Blossey, Peter N.  ^[1];

• Search DOE PAGES for author "Blossey, Peter N."
• Search DOE PAGES for ORCID "0000-0002-0352-0840"

McCoy, Isabel L.  ^[3]

• Search DOE PAGES for author "McCoy, Isabel L."
• Search DOE PAGES for ORCID "0000-0002-9989-0570"

---

+ Show Author Affiliations

1. Univ. of Washington, Seattle, WA (United States)
2. Univ. of Washington, Seattle, WA (United States); Allen Institute for Artificial Intelligence, Seattle, WA (United States)
3. University Corporation for Atmospheric Research Boulder, CO (United States); Univ. of Miami, FL (United States)

Publication Date:

Fri May 13 00:00:00 EDT 2022

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1874211

Grant/Contract Number:  

SC0020134

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Advances in Modeling Earth Systems

Additional Journal Information:

Journal Volume: 14; Journal Issue: 6; Journal ID: ISSN 1942-2466

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES