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Preprints
https://doi.org/10.5194/egusphere-2024-2397
https://doi.org/10.5194/egusphere-2024-2397
06 Aug 2024
 | 06 Aug 2024

Contributions of the synoptic meteorology to the seasonal CCN cycle over the Southern Ocean

Tahereh Alinejadtabrizi, Yi Huang, Francisco Lang, Steven Siems, Michael Manton, Luis Ackermann, Melita Keywood, Ruhi Humphries, Paul Krummel, Alastair Williams, and Greg Ayers

Abstract. Cloud Condensation Nuclei (CCN) play a fundamental role in determining the microphysical properties of low-level clouds, crucial for defining the energy budget over the Southern Ocean (SO), a region dominated by low-level clouds. Despite this importance, many aspects of the CCN budget over the SO remains poorly understood including the role of the synoptic meteorology. In this study, we classify the dominant synoptic meteorology over kennaook/Cape Grim Observatory (CGO) and examine its influence on the seasonal variation of the CCN concentration (NCCN).

Our analysis identifies six distinct synoptic regimes: three prevalent in the austral winter, when the subtropical ridge (STR) is strong and centred at lower latitudes, and three in the austral summer, when the STR shifts to higher latitudes. Distinct winter and summer ‘baseline’ regimes contribute to the seasonal cycle in NCCN over the SO with the winter baseline regime characterised by heavier precipitation, a deeper boundary layer and lower NCCN. An analysis of air mass back trajectories, specifically at the free troposphere level, supports this distinction, with wintertime baseline airmasses originating over higher latitudes. Across these two baseline regimes we observe a significant inverse relationship between precipitation and NCCN, underscoring the role of precipitation in reducing NCCN over the SO.

Using forward trajectories within this synoptic framework, we examine the transport of continental airmasses over the SO, finding that frontal air masses more frequently reach high latitudes during winter. We conclude that the location of the STR can moderate the advection of air masses between Antarctica and kennaook/Cape Grim.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Journal article(s) based on this preprint

28 Feb 2025
Contributions of the synoptic meteorology to the seasonal cloud condensation nuclei cycle over the Southern Ocean
Tahereh Alinejadtabrizi, Yi Huang, Francisco Lang, Steven Siems, Michael Manton, Luis Ackermann, Melita Keywood, Ruhi Humphries, Paul Krummel, Alastair Williams, and Greg Ayers
Atmos. Chem. Phys., 25, 2631–2648, https://doi.org/10.5194/acp-25-2631-2025,https://doi.org/10.5194/acp-25-2631-2025, 2025
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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Our research explores how weather patterns affect cloud-forming particles (CCN) over the...
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