Preprints
https://doi.org/10.5194/wcd-2021-41
https://doi.org/10.5194/wcd-2021-41

  02 Jul 2021

02 Jul 2021

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

Winter thermodynamic vertical structure in the Arctic atmosphere linked to large scale circulation

Tiina Nygård1, Michael Tjernström2, and Tuomas Naakka1 Tiina Nygård et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland
  • 2Department of Meteorology, and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

Abstract. Thermodynamic profiles are affected by both the large scale dynamics and the local processes, such as radiation, cloud formation and turbulence. Based on ERA5 reanalysis, radiosoundings and cloud cover observations from winters 2009–2018, this study demonstrates manifold impacts of large scale circulation on temperature and specific humidity profiles in the circumpolar Arctic north of 65° N. Characteristic wintertime circulation types are allocated using Self-Organizing Maps (SOMs). The study shows that influence of different large scale flows must be viewed as a progressing set of processes: (1) horizontal advection of heat and moisture, driven by circulation, lead to so-called first order effects on thermodynamic profiles and turbulent surface fluxes, and (2) the advection is followed by transformation of the air through various physical processes, causing second order effects. An example of second order effects is the associated cloud formation, which shifts the strongest radiative cooling from the surface to the cloud top. The temperature and specific humidity profiles are most sensitive to large scale circulation over the Eurasian land west of 90° E and the Arctic Ocean sea ice, whereas impacts over North America and Greenland are more ambiguous. Eurasian land, between 90° E and 140° E, occasionally receives warm and moist air from the northern North Atlantic, which, with the support of radiative impacts of clouds, weaken the otherwise strong temperature and specific humidity inversions. Altitudes of maximum temperature and specific humidity in a profile, and their variability between the circulation types, are good indicators of the depth of the layer impacted by surface–atmosphere processes interacting with the large scale circulation. Different circulation types typically cause variations of a few hundred meters to this altitude, and the layer impacted is deepest over north-eastern Eurasia and North America.

Tiina Nygård et al.

Status: open (until 19 Aug 2021)

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

Tiina Nygård et al.

Tiina Nygård et al.

Viewed

Total article views: 153 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
106 43 4 153 14 1 2
  • HTML: 106
  • PDF: 43
  • XML: 4
  • Total: 153
  • Supplement: 14
  • BibTeX: 1
  • EndNote: 2
Views and downloads (calculated since 02 Jul 2021)
Cumulative views and downloads (calculated since 02 Jul 2021)

Viewed (geographical distribution)

Total article views: 151 (including HTML, PDF, and XML) Thereof 151 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 01 Aug 2021
Download
Short summary
Temperature and humidity profiles in the Arctic atmosphere in winter are affected by both the large scale dynamics and the local processes, such as radiation, cloud formation and turbulence. Hence, the influence of different large scale flows on temperature and humidity profiles in the Arctic must be viewed as a progressing set of processes.