Preprints
https://doi.org/10.5194/egusphere-2023-629
https://doi.org/10.5194/egusphere-2023-629
13 Apr 2023
 | 13 Apr 2023

Determining the surface mixing layer height of the Arctic atmospheric boundary layer during polar night in cloudless and cloudy conditions

Elisa F. Akansu, Sandro Dahlke, Holger Siebert, and Manfred Wendisch

Abstract. This study analyzes turbulent properties in, and the thermodynamic structure of the Arctic atmospheric boundary layer (ABL) during winter and the transition to spring. These processes influence the evolution and longevity of clouds, and impact the surface radiative energy budget in the Arctic. For the measurements we have used an instrumental payload carried by a helium filled tethered balloon. This system was deployed between December 2019 and May 2020 during the yearlong Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Vertically highly resolved in situ measurements of profiles of turbulent parameters were obtained reaching from the sea ice up to several hundred meters height. The two typical states of the Arctic ABL were identified: cloudless situations with a shallow and stable ABL, and cloudy conditions maintaining a mixed ABL. We have used profile data to estimate the height of the surface mixing layer. For this purpose, a bulk Richardson number criterion approach was introduced. By deriving a critical bulk Richardson number for wintertime in high latitudes, we have extended the analysis to radiosonde data. Furthermore, we have tested the applicability of the Monin-Obukhov similarity theory to derive surface mixing layer heights based on measured surface fluxes.

Elisa F. Akansu et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-629', Anonymous Referee #1, 08 Jun 2023
  • RC2: 'Comment on egusphere-2023-629', Anonymous Referee #2, 27 Jun 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-629', Anonymous Referee #1, 08 Jun 2023
  • RC2: 'Comment on egusphere-2023-629', Anonymous Referee #2, 27 Jun 2023

Elisa F. Akansu et al.

Elisa F. Akansu et al.

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Latest update: 09 Dec 2023
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Short summary
The height of the mixing layer is an important factor for the surface-level distribution of energy or other substances. The experimental determination of this height – especially under the influence of clouds – is associated with large uncertainties, particularly under stable conditions that we often find during the polar night. We present a reference method using turbulence measurements on a tethered balloon, which allows us to evaluate approaches based on radiosondes or surface observations.