In fluence parameters for a polar mesocyclone development

Dierer, Silke; Schluenzen, K. Heinke

doi:10.1127/0941-2948/2005/0077

Cited by 12 publications

(10 citation statements)

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“…Within the next 6 hr, the katabatic flow from Ammassalik triggers a polar low with closed isobars on 29 February at 00 UTC and a core pressure of less than 980 hPa (Figure 2e). Converging flow, differential cold air advection decreasing with height in the Ammassalik area trigger the formation of the polar low (Klein & Heinemann, 2002) near the sea ice edge, where polar lows frequently form and intensify (Bracegirdle & Gray, 2009; Dierer & Schluenzen, 2005). There is also a two‐way interaction of the polar low‐level and the upper‐level trough.…”

Section: Synoptic Overview and Katabatic Storm Developmentmentioning

confidence: 99%

Air‐Sea Interactions and Water Mass Transformation During a Katabatic Storm in the Irminger Sea

et al. 2022

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We use a global 5‐km resolution model to analyze the air‐sea interactions during a katabatic storm in the Irminger Sea originating from the Ammassalik valleys. Katabatic storms have not yet been resolved in global climate models, raising the question of whether and how they modify water masses in the Irminger Sea. Our results show that dense water forms along the boundary current and on the shelf during the katabatic storm due to the heat loss caused by the high wind speeds and the strong temperature contrast. The dense water contributes to the lightest upper North Atlantic Deep Water as upper Irminger Sea Intermediate Water and thus to the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). The katabatic storm triggers a polar low, which in turn amplifies the near‐surface wind speed due to the superimposed pressure gradient, in addition to acceleration from a breaking mountain wave. Overall, katabatic storms account for up to 25% of the total heat loss (20 January 2020 to 30 September 2021) over the Irminger shelf of the Ammassalik area. Resolving katabatic storms in global models is therefore important for the formation of dense water in the western boundary current of the Irminger Sea, which is relevant to the AMOC, and for the large‐scale atmospheric circulation by triggering polar lows.

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Section: Synoptic Overview and Katabatic Storm Developmentmentioning

confidence: 99%

Air‐Sea Interactions and Water Mass Transformation During a Katabatic Storm in the Irminger Sea

et al. 2022

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“…We use the nonhydrostatic and anelastic atmospheric model METRAS [ Schlünzen , 1988, 1990] in a 2D version as applied earlier to cold air outbreaks by Lüpkes and Schlünzen [1996] and by Birnbaum and Lüpkes [2002] and to on‐ice flow regimes by Vihma et al [2003]. Its 3D version was applied to arctic regions by Dierer and Schlünzen [2005a, 2005b] and by Hebbinghaus et al [2006]. The model is originally a mesoscale model with horizontal grid spacing Δ x of at least 1 km in convective conditions.…”

Section: Model Descriptionmentioning

confidence: 99%

Modeling convection over arctic leads with LES and a non‐eddy‐resolving microscale model

et al. 2008

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[1] Turbulent heat transport over inhomogeneous surfaces with sharp temperature discontinuities is investigated with a focus on the flow over leads in sea ice. The main goal consists in the development of a turbulence closure for a microscale atmospheric model resolving the integrated effect of plumes emanated from leads, but not the individual convective eddies. To this end, 10 runs are carried out with a large eddy simulation (LES) model simulating the flow over leads for springtime atmospheric conditions with near-neutral inflow and a strong capping inversion. It is found that leads contribute to the stabilizing of the polar atmospheric boundary layer (ABL) and that strong countergradient fluxes of heat exist outside a core region of the plumes. These findings form the basis for the development of the new closure. It uses a new scaling with the internal ABL height and the characteristic vertical velocity for the plume region as the main governing parameters. Results of a microscale model obtained with the new closure agree well with the LES for variable meteorological forcing in case of lead orthogonal flow and for a fixed ABL height and lead width. The good agreement concerns especially the plume inclination, temperature, and heat fluxes as well as the relative contributions of gradient and countergradient transport of heat. A future more general closure should account, for example, for variable lead widths and wind directions. Results of the microscale model could be used to derive a future parameterization of the lead effect in large-scale models.Citation: Lüpkes, C., V. M. Gryanik, B. Witha, M. Gryschka, S. Raasch, and T. Gollnik (2008), Modeling convection over arctic leads with LES and a non-eddy-resolving microscale model,

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“…In addition to the standard variables from ERA5, we used the maximum Eady growth rate to assess the baroclinic instability in the atmosphere. Following earlier studies (Lindzen and Farrell, 1980;Dierer et al, 2005), we estimated the maximum Eady growth rate in the 1000 hPa to 750 hPa layer with σ E ≈ 0.31 f N | u750−u1000 z750−z1000 |, where f is the Coriolis frequency, u is the wind speed, z the height, N the Brunt-Väisälä frequency and the subscripts refer to the associated pressure levels.…”

Section: Datamentioning

confidence: 99%

North Atlantic freshwater events influence European weather in subsequent summers

Oltmanns

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et al. 2021

Preprint

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Abstract. Amplified Arctic ice loss in recent decades has been linked to increased occurrence of extreme mid-latitude weather. The underlying dynamical mechanisms remain elusive, however. Here, we demonstrate a novel mechanism linking freshwater releases into the North Atlantic with summer weather in Europe. Combining remote sensing, atmospheric reanalyses and model simulations, we show that freshwater events in summer trigger progressively sharper sea surface temperature gradients in subsequent winters, destabilising the overlying atmosphere and inducing a northward shift in the North Atlantic Current. In turn, the jet stream over the North Atlantic is deflected northward in the following summers, leading to warmer and drier weather over Europe. Our results suggest that growing Arctic freshwater fluxes will increase the risk of heat waves and droughts over the coming decades, and could yield enhanced predictability of European summer weather, months to years in advance.

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In fluence parameters for a polar mesocyclone development

Cited by 12 publications

References 0 publications

Air‐Sea Interactions and Water Mass Transformation During a Katabatic Storm in the Irminger Sea

Air‐Sea Interactions and Water Mass Transformation During a Katabatic Storm in the Irminger Sea

Modeling convection over arctic leads with LES and a non‐eddy‐resolving microscale model

North Atlantic freshwater events influence European weather in subsequent summers

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