Preprints
https://doi.org/10.5194/acp-2021-705
https://doi.org/10.5194/acp-2021-705

  22 Oct 2021

22 Oct 2021

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

Ship-based estimates of momentum transfer coefficient over sea ice and recommendations for its parameterization

Piyush Srivastava1,5, Ian M. Brooks1, John Prytherch2,6, Dominic J. Salisbury1, Andrew D. Elvidge3, Ian A. Renfrew3, and Margaret J. Yelland4 Piyush Srivastava et al.
  • 1School of Earth & Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 2Department of Meteorology, University of Stockholm, Stockholm, Sweden
  • 3School of Environmental Sciences, University of East Anglia, Norwich, UK
  • 4National Oceanography Centre, Southampton, UK
  • 5Centre of Excellence in Disaster and Mitigation and Management, Indian Institute of Technology, Roorkee, India
  • 6Bolin Centre for Climate Research, University of Stockholm, Stockholm, Sweden

Abstract. A major source of uncertainty in both climate projections and seasonal forecasting of sea ice is inadequate representation of surface–atmosphere exchange processes. The observations needed to improve understanding and reduce uncertainty in surface exchange parameterizations are challenging to make and rare. Here we present a large dataset of ship-based measurements of surface momentum exchange (surface drag) in the vicinity of sea ice from the Arctic Clouds in Summer Experiment (ACSE) in July–October 2014, and the Arctic Ocean 2016 experiment (AO2016) in August–September 2016. The combined dataset provides an extensive record of momentum flux over a wide range of surface conditions spanning the late summer melt and early autumn freeze-up periods, and a wide range of atmospheric stabilities. Surface exchange coefficients are estimated from in situ eddy covariance measurements. The local sea-ice fraction is determined via automated processing of imagery from ship-mounted cameras. The surface drag coefficient, CD10n, peaks at local ice fractions of 0.6–0.8, consistent with both recent aircraft-based observations and theory. Two state-of-the-art parameterizations have been tuned to our observations with both providing excellent fits to the measurements.

Piyush Srivastava et al.

Status: open (until 03 Dec 2021)

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

Piyush Srivastava et al.

Piyush Srivastava et al.

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Short summary
The parameterization of surface turbulent fluxes over sea ice remains a weak point in both weather forecast and climate models. Recent theoretical developments have introduced more extensive physics but these descriptions are poorly constrained due to a lack of observation data. Here we utilize a large data set of in situ measurements of turbulent fluxes over sea ice to tune the latest state-of-the-art parameterization of wind stress, and compare it with a previous, less comprehensive scheme.
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