Publication Date:
2017-10-20
Description:
A nonhydrostatic model (NH3D) is used for idealized dry quasi 2-D simulations of
Arctic cold-air outbreaks using horizontal grid spacings between 1.25 and 60 km. Despite
the idealized setup, the model results agree well with observations over Fram Strait. It is
shown that an important characteristic of the flow regime during cold-air outbreaks is an
ice-breeze jet (IBJ) with a maximum wind speed exceeding often the large-scale
geostrophic wind speed. According to the present simulations, which agree very well with
those of another nonhydrostatic mesoscale model (METRAS), the occurrence, strength,
and horizontal extent L of this jet depend strongly on the external forcing and especially on
the direction of the large-scale geostrophic wind relative to the orientation of the ice edge.
The latter dependency is explained by the effects of the thermally induced geostrophic
wind over open water and Coriolis force. It is found that coarse-resolution runs
underestimate the strength of the jet. This underestimation has important consequences to
the surface fluxes of heat and momentum, which are also underestimated by about
10–15% on average over the region between the ice edge and 120–180 km downstream.
Our results suggest that a grid spacing of about L/7 is required (about 10–30 km) to
simulate the IBJ strength with an accuracy of at least 10%. Thus, the results of large-scale
models as well might contain uncertainties with regard to the simulated IBJ strength which
would influence the energy budget in a large region along the marginal sea ice zones.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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