Preprints
https://doi.org/10.5194/acp-2021-681
https://doi.org/10.5194/acp-2021-681

  14 Sep 2021

14 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

A climatology of open and closed mesoscale cellular convection over the Southern Ocean derived from Himawari-8 observations

Francisco Lang1, Luis Ackermann1,2, Yi Huang2,3, Son C. H. Truong1,2, Steven T. Siems1,2, and Michael J. Manton1 Francisco Lang et al.
  • 1School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia
  • 2Australian Research Council Centre of Excellence for Climate Extremes (CLEX), Melbourne, VIC, Australia
  • 3School of Earth Sciences, The University of Melbourne, Melbourne, VIC, Australia

Abstract. Marine atmospheric boundary layer clouds cover vast areas of the Southern Ocean (SO), where they are commonly organized into mesoscale cellular convection (MCC). Using three years of Himawari-8 geostationary satellite observations, open and closed MCC structures are identified using a hybrid convolutional neural network. The results of the climatology show that open MCC clouds are roughly uniformly distributed over the SO storm track across mid-latitudes, while closed MCC clouds are most predominant in the southeast Indian Ocean with a second maximum along the storm track. The ocean polar front, derived from ECMWF-ERA5 sea surface temperature gradients, is found to be aligned with the southern boundaries for both MCC types. Along the storm track, both closed and open MCCs are commonly located in post-frontal, cold air masses. The hourly classification of closed MCC reveals a pronounced daily cycle, with a peak occurring late night/early morning. Seasonally, the diurnal cycle of closed MCC is most intense during the summer months (DJF). Conversely, almost no diurnal cycle is evident for open MCC.

Francisco Lang et al.

Status: open (until 26 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Francisco Lang et al.

Francisco Lang et al.

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Short summary
Marine low-level clouds cover vast areas of the Southern Ocean, and they are essential to the Earth system energy balance. Three years of satellite observations are used to group low-level clouds by their spatial structure using a pattern-recognizing program. Two primary cloud-type patterns are studied: open and closed clouds. Open clouds are uniformly distributed over the storm track, while closed clouds are most predominant in the southeast Indian Ocean. Closed clouds exhibit a daily cycle.
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