Mesoscale Modelling of the Arctic Atmospheric Boundary Layer and Its Interaction with Sea Ice

Abstract

This chapter summarises mesoscale modelling studies, which were carried out during the ACSYS decade until 2005. They were aiming at the parameterisation and improved understanding of processes in the Arctic boundary layer over the open ocean and marginal sea ice zones and over the Greenland ice sheet. It is shown that progress has been achieved with the parameterization of fluxes in strong convective situations such as cold-air outbreaks and convection over leads. A first step was made towards the parameterization of the lead-induced turbulence for high-resolution, but non-eddy resolving models. Progress has also been made with the parameterization of the near-surface atmospheric fluxes of energy and momentum modified by sea ice pressure ridges and by ice floe edges. Other studies brought new insight into the complex processes influencing sea ice transport and atmospheric stability over sea ice. Improved understanding was obtained on the cloud effects on the snow/ice surface temperature and further on the near-surface turbulent fluxes. Finally, open questions are addressed, which remained after the ACSYS decade for future programmes having been started in the years after 2005

Aircraft‐based observations of atmospheric boundary‐layer modification over Arctic leads

“…Dare and Atkinson, ). A comprehensive summary of previous studies on lead–atmosphere interactions can be found in Vihma et al () and Lüupkes et al (, ), but some findings will be summarized in the following to demonstrate the relevance of the present study.…”

“…Measurements of the surface energy budget over a large sea‐ice‐covered region could be most effective when the flight patterns could be restricted to long transect flights directed straight ahead and crossing a large number of different leads (as performed by Brümmer and Thiemann, ; Lüpkes et al , ). However, this is only possible when an arbitrary orientation of a flight track relative to the orientation of a lead is sufficient for the determination of fluxes.…”

“…A shortcoming of these campaigns was that measurements were only conducted over the sea ice surrounding the leads. However, flux measurements directly over a lead were carried out during the Winter Arctic Polynya Study (WARPS; Lüpkes et al , ) using a mast installed on RVPolarstern as well as the helicopter‐borne turbulence probe HELIPOD (Bange et al , ). Besides a large sensitivity of the turbulent heat fluxes to the ice cover on the lead, this study showed that turbulent heat fluxes of the atmospheric boundary layer (ABL) were highest over wide leads.…”

A parametrization, based on sea ice morphology, of the neutral atmospheric drag coefficients for weather prediction and climate models

“…The parametrization of the MIZ surface roughness has been discussed intensively during the last three decades, starting with studies by Overland [1985] and Guest and Davidson [1987]. A general finding of Andreas et al [1984], Hanssen‐Bauer and Gjessing [1988], Stössel and Claussen [1993], Mai et al [1996], Birnbaum and Lüpkes [2002], Lüpkes and Birnbaum [2005], and Lüpkes et al [2012] was that atmospheric momentum fluxes are influenced not only by the skin drag of the open water surface and of the more or less plane ice floe surfaces but also by the form drag caused by the edges of floes, where often small ridges form due to floe collisions. So, the effective atmospheric drag over the MIZ was parametrized by accounting for both skin drag and form drag using schemes of different complexity.…”

The impact of heterogeneous surface temperatures on the 2-m air temperature over the Arctic Ocean under clear skies in spring

“…In the first approach it is set to a constant value. Two different values are applied that are typical for the Arctic BL (Lüpkes et al, 2012b). The first one, 350 m, was, for example, measured over a flaw lead polynya in the Canadian Archipelago by Raddatz et al (2011).…”