Surface-Pressure Change through Loewe's Phenomena and Katabatic Flow Jumps: Study of Two Cases in Adélie Land, Antarctica

Pettré, Paul; André, Jean‐Claude

doi:10.1175/1520-0469(1991)048<0557:spctlp>2.0.co;2

Cited by 55 publications

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“…The abrupt cessation of katabatic flows has been observed before in surface pressure, temperature and horizontal wind data (e.g. Pettré and André 1991). Here it is clear that the cessation occurs throughout the boundary layer and there is a dramatic vertical velocity response that is coherent with height.…”

Section: Two Case-studies Of Katabatic Flowsupporting

confidence: 66%

“…Subsequently automatic weather stations (AWS) provided the means to obtain a high temporal-resolution year-round picture of the surface winds and, although numerous technical problems have been endured, these remain a mainstay of katabatic-flow studies (e.g. Parish 1988; Stearns and Wendler 1988;Bromwich 1989;Pettré and André 1991;King 1993;Renfrew and Anderson 2002) their main limitation being that the height of the AWS mast (typically 3 m) usually allows only one level of near-surface wind measurement.…”

Section: Introductionmentioning

confidence: 99%

“…Over western and eastern Greenland, Heinemann (1999Heinemann ( , 2002 used a research aircraft to obtain numerous soundings of early summer katabatic flows and, due to the comprehensive sampling carried out, was able to quantify the momentum budget of the flow and its turbulent structure. Over Adélie Land, in Antarctica, as part of the IAGO (Interaction Atmosphere-Glace-Ocean) campaign, Sorbjan et al (1986) and Pettré and André (1991) used tethersonde and radiosonde observations to describe the summertime atmospheric boundary layer. Near Siple Coast, Bromwich and Liu (1996) used sodar, a radio acoustic sounding system and radiosonde soundings to describe summertime katabatic flows; while over Dronning Maud Land, Bintanja (2000a,b) combined simultaneous tethersonde and radiosonde soundings to calculate an approximate momentum budget of summertime katabatic flow.…”

Section: Introductionmentioning

confidence: 99%

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Profiles of katabatic flow in summer and winter over Coats Land, Antarctica

Renfrew

Anderson

2006

Quart J Royal Meteoro Soc

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SUMMARYObservations from a novel autonomous Doppler sodar wind profiling system are described and analysed. These include the first continuous wintertime soundings of katabatic winds over Antarctica-a continent with which they are synonymous. During 2002 and 2003 over 2600 wind profiles were taken during 'case-studies' of high-resolution sounding lasting hours to days. These case-studies have been subjectively classified as: synoptically driven, katabatically influenced (28 days); primarily katabatically driven flows (a subset of 16 days); or other flow types. The Doppler sodar observations were augmented by automatic weather station observations at the field site and further up the slope, as well as synoptic and upper-air observations at Halley Research Station, some 50 km distant on the Brunt Ice Shelf.In primarily katabatic flows there is a systematic change in the shape and depth of the low-level katabatic jet with wind speed. Relatively strong katabatic flows (maximum winds of typically 8-10 m s −1 ) have a jet maximum between 20 and 60 m above the surface and are relatively deep (up to 200 m); while moderate katabatic flows (4-8 m s −1 ) typically have a jet maximum between 3 and 30 m and are shallower (∼100 m), although they can also be more diffuse in structure with a wind speed maximum at higher altitude. In all katabatic flows there is backing of wind direction with height, consistent with decreasing friction away from the surface. During summertime katabatic flows there is a clear diurnal signature at all heights, although this is less pronounced in the surface layer where there seems to be a persistent 2-4 m s −1 katabatic flow during all case-studies. Where the diurnal forcing results in an abrupt katabatic flow deceleration, i.e. what may be a katabatic 'jump', there is a concurrent vertical acceleration. Wind profiles from a recent numerical weather prediction study of idealized katabatic flows at this site compare favourably with selected mean profiles; the only significant difference is that the model's wind speed is too low over the lowest ∼10 m.

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Section: Two Case-studies Of Katabatic Flowsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Profiles of katabatic flow in summer and winter over Coats Land, Antarctica

Renfrew

Anderson

2006

Quart J Royal Meteoro Soc

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“…In a strictly two-layer fluid flow these transitions of flow type would be through flow discontinuities or hydraulic jumps; indeed, such jumps have been observed in katabatic flows (e.g. Lied 1964;Pettré and André 1991). In this case the Fr variations are relatively small and, as the model is multi-level, the flow remains continuous.…”

Section: An Analysis Of the Katabatic Flow Dynamicsmentioning

confidence: 95%

The dynamics of idealized katabatic flow over a moderate slope and ice shelf

Renfrew

2004

Quart J Royal Meteoro Soc

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SUMMARYA non-hydrostatic numerical weather prediction model has been employed to simulate idealized katabatic flows over a moderate slope and adjoining ice shelf. The topography of Coats Land and the adjoining Brunt Ice Shelf, Antarctica, has been used; this is typical of much of the Antarctic coastline. The Regional Atmospheric Modeling System Version 4.3 has been adapted for simulations over compacted snow, most notably through changes to the multi-layer soil model. The simulations are initialized using clear-sky conditions and at rest. On the slope, a shallow katabatic flow develops, the winds becoming approximately steady on the slope by ∼12 h. The peak downslope winds are about 7 m s −1 at 30 m above the snow surface. The katabatic flow depth ranges from 50 to 100 m down the slope. Over the ice shelf the katabatic flow peters out, while a pool of cold air develops, primarily through sensible-heat loss into the surface and partially balancing the net radiative-heat loss to space. Near-surface and sounding data from the model simulations compare well with archetypal and typical katabatic flow observations, especially after some tuning of the model's turbulence parametrization.An analysis of the downslope flow dynamics shows the buoyancy force is generally balanced by the inertial force, except towards the foot of the slope where it is balanced by upslope forces related to gradients in the potential-temperature deficit and katabatic-layer height, caused by the pool of cold air over the ice shelf. Over time, the cooling of the ice shelf boundary layer leads to an apparent retreat of the katabatic flow from the ice shelf and some way up the slope. The dynamical analysis explains the surface climatology observed, such that the persistent katabatic winds of Coats Land rarely reach the Brunt Ice Shelf. The simulated katabatic flow moves from 'shooting' to 'tranquil' towards the foot of the slope. This transition acts to trigger a train of internal gravity waves which propagate energy upwards away from the katabatic flow jump. Previous studies have also found shooting to tranquil katabatic flow transitions, so to generalize these findings would suggest that internal gravitywave generation is ubiquitous around much of coastal Antarctica and Greenland.

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“…Due to the high reflectivity of the snow and its radiative properties the Antarctic continent acts as a strong heat 0921-8181/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved E0059-8 sink, which results in an almost ever present surface-based inversion. A considerable number of observational studies have been carried out in Antarctica (Parish, 1981;Schwerdtfeger, 1984;Heinemann, 1988;Pettre and Andre, 1991). Lately satellites have also been used to study Antarctic katabatic winds (Bromwich 1989).…”

Section: Introductionmentioning

confidence: 99%

The observed katabatic flow at the edge of the Greenland ice sheet during GIMEX-91

Broeke

Duynkerke

Oerlemans

1994

Global and Planetary Change

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Observations performed in the melting zone of the Greenland ice sheet and over the adjacent tundra in the summer of 1991 are described. The experimental area is the region near St ndre Stromfjord (67°N, 54°W), which is relatively dry and sunny, resulting in the highest mean temperature in Greenland in July. The katabatic wind is dominantly present over the ice; it influences the energy balance near the surface through the sensible and latent heat flux. With the aid of a tethered balloon it was observed that the thickness of the katabatic layer is typically 100 to 200 m. An interesting aspect of the katabatic wind appears to be the acceleration of the flow in the late afternoon due to the large temperature gradient at the border between tundra and ice. Further on the ice, this effect is no longer important for the dynamics of the katabatic flow. The net radiation is the main driving force there. An attempt is made to estimate the importance of these thermal wind effects compared to the buoyancy forcing. It is concluded that near the edge of the ice surface winds are driven by the horizontal pressure gradient, imposed by the thermal contrast between tundra and ice. A comparison is made between the observed katabatic wind and those in the Antarctic.

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Surface-Pressure Change through Loewe's Phenomena and Katabatic Flow Jumps: Study of Two Cases in Adélie Land, Antarctica

Cited by 55 publications

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Profiles of katabatic flow in summer and winter over Coats Land, Antarctica

Profiles of katabatic flow in summer and winter over Coats Land, Antarctica

The dynamics of idealized katabatic flow over a moderate slope and ice shelf

The observed katabatic flow at the edge of the Greenland ice sheet during GIMEX-91

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