Identification

Title

Marine boundary layer cloud condensation Nuclei bias over the Southern Ocean: Comparisons between the community atmosphere model 6 and field observations

Abstract

Marine boundary layer (MBL) clouds play a crucial role in regulating radiative balance in the atmosphere. Previous studies identified that MBL cloud droplet number concentration (Nd) is underestimated by a factor of 2 over the summertime Southern Ocean (SO) close to the Antarctic coast in many models. Here, comparisons between cloud condensation nuclei (CCN) observations from field campaigns during the 2017–2018 Austral summer over the Australasian sector of the SO and simulated CCN from the Community Atmospheric Model 6 (CAM6) are presented. Modeled MBL CCN number concentration (N CCN ) is underestimated, by close to 100% at latitudes south of 55°S with the N CCN bias (a) largest close to the Antarctic Plateau during summer, implying the biased CCN type has seasonal and latitudinal variation and, (b) three times larger over sea ice than over open water, implying sea spray CCN are better simulated compared to secondary CCN. Assessments of aerosol size distributions indicate an underestimation of accumulation‐mode‐aerosols (Ac) with diameters 70 nm < D < 100 nm. CCN supersaturation spectra indicate that the observed CCN had lower hygroscopicity compared to simulated CCN, implying differences in CCN chemical composition. With secondary aerosols including sulfate being less hygroscopic than sea salt CCN, the CCN activation ratio derived using bulk hygroscopicity kappa in the Abdul‐Razzak function leads to an underestimation of critical supersaturation south of 62°S. The biases reported here highlight important shortfalls in simulated CCN that can be important to the well‐documented underestimated N d by Earth System Models, a key feature and uncertainty of pre‐industrial conditions.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.net/ark:/85065/d7668jms

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2025-04-28T00:00:00Z

Frequency of update

Quality and validity

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Conformity

Data format

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Constraints related to access and use

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Use constraints

<span style="font-family:Arial;font-size:10pt;font-style:normal;" data-sheets-root="1">Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.</span>

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact