An ice breeze mechanism for boundary-layer jets

Langland, Rolf H.; Tag, Paul M.; Fett, Robert W.

doi:10.1007/bf00121789

Cited by 18 publications

(11 citation statements)

References 22 publications

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“…Collocated inversions are present in 65% of the profiles. Low-level wind speed maxima, commonly known as low-level jets (LLJs), can occur for several reasons: for example, as inertial oscillations after frictional decoupling at the surface (Andreas et al 2000) or because of low-level baroclinicity (Langland et al 1989), for example, associated with the ice edge. Many different criteria to detect LLJs are found in the literature (Stull 1988;Andreas et al 2000;Baas et al 2009).…”

Section: B Analysis Methodsmentioning

confidence: 99%

Atmospheric Conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting Open Water and Sea Ice Surfaces during Melt and Freeze-Up Seasons

et al. 2016

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The Arctic Clouds in Summer Experiment (ACSE) was conducted during summer and early autumn 2014, providing a detailed view of the seasonal transition from ice melt into freeze-up. Measurements were taken over both ice-free and ice-covered surfaces near the ice edge, offering insight into the role of the surface state in shaping the atmospheric conditions. The initiation of the autumn freeze-up was related to a change in air mass, rather than to changes in solar radiation alone; the lower atmosphere cooled abruptly, leading to a surface heat loss. During melt season, strong surface inversions persisted over the ice, while elevated inversions were more frequent over open water. These differences disappeared during autumn freeze-up, when elevated inversions persisted over both ice-free and ice-covered conditions. These results are in contrast to previous studies that found a well-mixed boundary layer persisting in summer and an increased frequency of surface-based inversions in autumn, suggesting that knowledge derived from measurements taken within the pan-Arctic area and on the central ice pack does not necessarily apply closer to the ice edge. This study offers an insight into the atmospheric processes that occur during a crucial period of the year; understanding and accurately modeling these processes is essential for the improvement of ice-extent predictions and future Arctic climate projections.

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Section: B Analysis Methodsmentioning

confidence: 99%

Atmospheric Conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting Open Water and Sea Ice Surfaces during Melt and Freeze-Up Seasons

et al. 2016

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“…The growth of wind speed over the open water was discussed in several studies. In some of these studies [ Overland et al , ; Langland et al , ; Guest et al , ], one of the proposed reasons for this was the baroclinicity related to the surface heating over open water. This mechanism is often referred to as an ice‐breeze circulation (IBC).…”

Section: Introductionmentioning

confidence: 99%

Idealized dry quasi 2‐D mesoscale simulations of cold‐air outbreaks over the marginal sea ice zone with fine and coarse resolution

et al. 2013

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[1] 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.

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“…Under a constant easterly geostrophic wind forcing in the free troposphere, such wind shear strengthens the easterly winds below compared to the condition when the temperature gradient is not present, which favors the subgeostrophic LLJ formation near the top of the boundary layer (Figure ). They are considered to be closely associated with the LLJs in the Arctic and near the sea ice edge (Jakobson et al, ; Langland et al, ; Vihma et al, ). The wind speed profile calculated by integrating the thermal wind from the top of a LLJ to the center of the LLJ matched well with the rawinsonde observations for a LLJ case observed during the Sea State cruise in the fall of 2015 (Guest et al, ; Persson et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…The wind speed profile calculated by integrating the thermal wind from the top of a LLJ to the center of the LLJ matched well with the rawinsonde observations for a LLJ case observed during the Sea State cruise in the fall of 2015 (Guest et al, ; Persson et al, ). The thermal contrast across the sea ice edge can also induce a secondary “ice breeze” circulation, similar to the sea breeze circulation, and the resulting off‐ice wind acceleration can strengthen low‐level and surface winds near the sea ice edge (Guest et al, ; Langland et al, ; Overland et al, ). With off‐ice winds, such as during cold air outbreaks, this mechanism is crucial for the generation of the “ice breeze jet” downwind of the sea ice edge over open water (Chechin et al, ).…”

Section: Introductionmentioning

confidence: 99%

Low‐Level and Surface Wind Jets Near Sea Ice Edge in the Beaufort Sea in Late Autumn

Liu

Schweiger

2019

JGR Atmospheres

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Low‐level wind jets (LLJs) and strong surface winds are frequently observed near the sea ice edge in the presence of strong thermal contrast between open water and sea ice. Two LLJ cases near the sea ice edge in the Beaufort Sea are examined using dropsonde observations made from Seasonal Ice Zone Reconnaissance Survey flights. Ensembles of Polar Weather Research and Forecast simulations with and without sea ice demonstrate the contribution of the surface thermal contrast to the boundary layer structure, the LLJ, and surface ice edge jets. Because the surface temperature contrast only influences the lower most hundreds of meters in the atmospheric boundary layer, its contribution to the temperature gradient and wind speed at the level of the LLJ is limited. The sea ice does strengthen the LLJ by extending the LLJ northward over sea ice and increasing the maximum LLJ wind speeds by up to 13% and as much as 29% further north at a lower altitude. However, the primary reason for the observed strong winds in these two cases are the synoptic interactions between anticyclones and approaching cyclones. The effect of the surface thermal contrast on surface winds is controlled by a separate mechanism. The cold and stable boundary layer over sea ice prevents the momentum transport from the LLJ to the surface. This leads to weaker surface winds over sea ice and confines the strong surface winds close to the sea ice edge. This mechanism contributes to the frequent occurrence of the surface “ice edge jets.”

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An ice breeze mechanism for boundary-layer jets

Abstract: The existence of a low-level

Cited by 18 publications

References 22 publications

Atmospheric Conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting Open Water and Sea Ice Surfaces during Melt and Freeze-Up Seasons

Atmospheric Conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting Open Water and Sea Ice Surfaces during Melt and Freeze-Up Seasons

Idealized dry quasi 2‐D mesoscale simulations of cold‐air outbreaks over the marginal sea ice zone with fine and coarse resolution

Low‐Level and Surface Wind Jets Near Sea Ice Edge in the Beaufort Sea in Late Autumn

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