Modelling and observations of the katabatic flow dynamics over
                        Greenland

Heinemann, Günther; Klein, Thomas

doi:10.3402/tellusa.v54i5.12167

Cited by 39 publications

(36 citation statements)

References 18 publications

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“…Also the Greenland surface wind velocities in summer are generally lower than in winter, which can be attributed to the strength in the katabatic forcing (Ettema et al, 2010), as in winter strong radiative cooling over the high-elevation ice dome results in a larger amount of cold dense air masses which are accelerated downslope. Overall, the local and large-scale circulation simulated in EEMpd are in good agreement with previous studies describing the present atmospheric flow over and around Greenland based on observations (Steffen and Box, 2001;Heinemann and Klein, 2002) or climate models (Ettema et al, 2010;Hakuba et al, 2012).…”

Section: Atmospheric Circulation In Eempdsupporting

confidence: 78%

“…In addition, the area of strongest surface winds follows the ice sheet margin (e.g., compare EEMpd and EEMr3 in Fig. 7) since the steep slopes have the largest katabatic potential (Heinemann and Klein, 2002). In contrast, the areas which become flat and ice-free (e.g., northern Greenland in EEMr2) experience a drastic reduction in surface wind speed.…”

Section: Atmospheric Circulation With Reduced Grismentioning

confidence: 99%

“…The mean surface winds, thus, result in a clear outflow of air from Greenland whereby the downslope winds are deflected to the right due to the Coriolis force. The surface winds during winter are particularly strong in northwestern Greenland where the pressure gradient resulting from the low-pressure system over Baffin Bay coincides with the katabatic force (Heinemann and Klein, 2002).…”

Section: Atmospheric Circulation In Eempdmentioning

confidence: 99%

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Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

et al. 2014

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Abstract. The influence of a reduced Greenland Ice Sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a set of simulations with different GrIS realizations performed with a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation, which influences SAT through the lapse rate effect. The resulting lapse-rate-corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the Northern Hemisphere (NH) flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHF). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHF. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHF, and anomalous low winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the Eemian ice found in the NEEM core, our model suggests that up to 3.1 • C of the annual mean Eemian warming can be attributed to these topographyrelated processes and hence is not necessarily linked to largescale climate variations.

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Section: Atmospheric Circulation In Eempdsupporting

confidence: 78%

Section: Atmospheric Circulation With Reduced Grismentioning

confidence: 99%

Section: Atmospheric Circulation In Eempdmentioning

confidence: 99%

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Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

et al. 2014

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“…As the third largest mountain range in the Northern Hemisphere, it has an important influence on the local air flow and plays a major role in gravity-wave generation (Petersen et al, 2005), cyclogenesis (Kristjánsson and McInnes, 1999) and the formation of katabatic flows (Heinemann and Klein, 2002). Furthermore, interactions between Greenland and the cyclones passing close by on the North Atlantic storm track give rise to a number of topographically forced weather systems such as barrier flows and tip jets (Moore and Renfrew, 2005;Renfrew et al, 2008;Renfrew et al, 2009a).…”

Section: Introductionmentioning

confidence: 99%

An easterly tip jet off Cape Farewell, Greenland. II: Simulations and dynamics

Outten

Renfrew

Petersen

2009

Quart J Royal Meteoro Soc

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An easterly tip jet that occurred on 21 February 2007 off Cape Farewell, Greenland, is examined. In Part I of this article aircraft observations were described. Now, in Part II, numerical simulations and an analysis of the dynamical forcing mechanisms are presented. The simulations make use of a limited-area 12 km resolution configuration of the Met Office's Unified Model. Sea-surface temperatures and sea-ice concentrations have been replaced using the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) product, addressing a boundary-layer temperature bias, while roughness lengths over sea ice have been updated, addressing a wind-speed bias. These modifications ensured a reasonably accurate simulation: generally within 1-2 K and 2-3 m s −1 when compared with dropsonde observations. A momentumbudget analysis along a curved locus through the core of the jet has been derived. Off southeast Greenland, the easterly tip jet was in cross-jet geostrophic balance, but was being accelerated downstream by an along-jet pressure gradient. Over the curved part of the locus, as the jet rounded Cape Farewell, a cross-jet residual suggests that the jet was unbalanced at the height of the jet core. This residual decreases with height so that an approximate gradient wind balance applies in the upper part of the jet. The anticyclonic curvature, characteristic of easterly tip jets, was caused by a dramatic decrease in the cross-jet pressure-gradient force at the end of the barrier, after which the jet aligned with the synoptic-scale isobars and returned to approximate geostrophic balance. The momentum budget is shown to be robust and applicable to other cases.

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“…Heinemann and Klein, 2002). Klein and Heinemann (2002) suggested that convergence of the outflowing air from the katabatic flow in the valleys of east Greenland might be responsible for the formation of mesocyclones over the Denmark Strait, and found support for this view from model simulations.…”

Section: Introductionmentioning

confidence: 72%

Orographic influence of east Greenland on a polar low over the Denmark Strait

Kristjánsson

Þorsteinsson

Kolstad

et al. 2011

Quart J Royal Meteoro Soc

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We present a numerical study of a polar low which hit western Iceland in January 2007, with heavy snowfall and mean wind speeds exceeding 20 m s −1 in several locations. The operational models at the time captured the polar low formation rather well, but there was a large spread in their predictions of the subsequent evolution and track of the polar low. The objective of this study is to investigate possible orographic forcing from Greenland as a trigger for the polar low development. In addition to an analysis of surface observations and satellite imagery, sensitivity studies using HIRLAM were carried out with various degradations of Greenland's orography, as well as with modifications to the sea-surface temperature (SST), surface roughness and the data assimilation scheme. Despite the presence of an upper-level trough and weak static stability in all the simulations, the polar low development was found to be very sensitive to the presence of the high mountains of eastern Greenland. Whereas the control run captured well the main features of the polar low, simulations with parts of east Greenland's orography removed gave a southward-displaced polar low which moved rapidly eastward, resulting in substantially underestimated nearsurface winds and snowfall amounts. Setting the orographic heights over all of Greenland to zero led to the complete disappearance of the polar low. On the other hand, artificially increasing the SST by 4 K in the Denmark Strait, reducing the orographic roughness or replacing the four-dimensional variational assimilation scheme (4D-Var) by 3D-Var had only a small effect on the polar low. We suggest that hitherto unreported interactions between the high mountains of east Greenland and polar low development over the Denmark Strait may be more important for polar low formation than katabatic flow from valleys in east Greenland that was highlighted in earlier studies.

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Modelling and observations of the katabatic flow dynamics over Greenland

Cited by 39 publications

References 18 publications

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

An easterly tip jet off Cape Farewell, Greenland. II: Simulations and dynamics

Orographic influence of east Greenland on a polar low over the Denmark Strait

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