Abstract
In the polar regions, the atmospheric boundary layer (ABL) characteristics are strongly influenced by convection over leads, which are elongated channels in the sea ice covered ocean. The effects on the ABL depend on meteorological forcing and lead geometry. In non-convection-resolving models, in which several leads of potentially different characteristics might be present in a single grid cell, such surface characteristics and the corresponding ABL patterns are not resolved. Our main goal is to investigate potential implications for such models when these subgrid-scale patterns are not considered appropriately. We performed non-eddy-resolving microscale simulations over five different domains with leads of different widths separated by 100% sea ice. We also performed coarser-resolved simulations over a domain representing a few grid cells of a regional climate model, wherein leads were not resolved but accounted for via a fractional sea ice cover of 91% in each cell. Domain size and mean sea ice concentration were the same in all simulations. Differences in the domain-averaged ABL profiles and patterns of wind, temperature, and turbulent fluxes indicate a strong impact of both the leads and their geometry. Additional evaluations of different turbulence parameterizations show large effects by both gradient-independent heat transport and vertical entrainment.
Highlights
In the polar sea ice regions, the magnitude of transport mechanisms across the surface–atmosphere interface and, the near-surface energy budget are strongly related to the characteristics of the surface, such as sea ice concentration, sea ice thickness, and surface temperatures
We show domain-averaged vertical profiles of both mean atmospheric quantities and turbulent fluxes to point at the differences in the atmospheric boundary layer (ABL) structures caused by the different lead patterns and different parameterizations
Our results show that the actual configuration of leads in a sea ice covered region has a clear influence on ABL characteristics, which was obvious in the respective ABL structures over the individual domains, as well as in the domain-averaged vertical profiles of wind, temperature, and turbulent fluxes
Summary
Atmosphere interface and, the near-surface energy budget are strongly related to the characteristics of the surface, such as sea ice concentration, sea ice thickness, and surface temperatures. Both leads and polynyas are either free of ice or are covered with thin ice only In this season, their surface is up to 40 K warmer than the air as long as no new ice has developed. This causes strong convection (convective plumes) and increased turbulent motion in convective internal boundary layers (IBL). They develop inside the atmospheric boundary layer (ABL) over the horizontally inhomogeneous environment of the leads (see Figure 1)
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