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1
Yu, Lejiang, Shiyuan Zhong, and Bo Sun. "The Climatology and Trend of Surface Wind Speed over Antarctica and the Southern Ocean and the Implication to Wind Energy Application." Atmosphere 11, no. 1 (2020): 108. http://dx.doi.org/10.3390/atmos11010108.
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Surface wind trends and variability over Antarctica and the Southern Ocean and their implications to wind energy in the region are analyzed using the gridded ERA-Interim reanalysis data between 1979 and 2017 and the Self-Organizing Map (SOM) technique. In general, surface winds are stronger over the coastal regions of East Antarctica and the Transantarctic Mountains and weaker over the Ross and Ronne ice shelves and the Antarctic Peninsula; and stronger in winter and weaker in summer. Winds in the southern Indian and Pacific Oceans and along coastal regions exhibit a strong interannual variability that appears to be correlated to the Antarctic Oscillation (AAO) index. A significantly positive trend in surface wind speeds is found across most regions and about 20% and 17% of the austral autumn and summer wind trends, respectively, and less than 1% of the winter and spring wind trends may be explained by the trends in the AAO index. Except for the Antarctic Peninsula, Ronne and Ross ice shelves, and small areas in the interior East Antarctica, most of the continent is found to be suitable for the development of wind power.
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Kodama, Yuji, Gerd Wendler, and Joan Gosink. "The Effect of Blowing Snow on Katabatic Winds in Antarctica." Annals of Glaciology 6 (1985): 59–62. http://dx.doi.org/10.3189/1985aog6-1-59-62.
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An acceleration of the katabatic winds during periods of blowing snow was observed in Adelie Land, Antarctica. Data collected by Automatic Weather Stations' (AWS) showed a change in the relationship between the katabatic term of the surface geostrophic wind (katabatic force) and the wind speed for periods of blowing snow. When measurements of the katabatic force were plotted against the cube of the wind speed, the slope was steeper for wind speeds at less than a threshold speed for blowing snow. The difference between these two slopes was partly explained by the effect of blowing snow entrained into the atmospheric boundary layer.
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Kodama, Yuji, Gerd Wendler, and Joan Gosink. "The Effect of Blowing Snow on Katabatic Winds in Antarctica." Annals of Glaciology 6 (1985): 59–62. http://dx.doi.org/10.1017/s026030550000999x.
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An acceleration of the katabatic winds during periods of blowing snow was observed in Adelie Land, Antarctica. Data collected by Automatic Weather Stations' (AWS) showed a change in the relationship between the katabatic term of the surface geostrophic wind (katabatic force) and the wind speed for periods of blowing snow. When measurements of the katabatic force were plotted against the cube of the wind speed, the slope was steeper for wind speeds at less than a threshold speed for blowing snow. The difference between these two slopes was partly explained by the effect of blowing snow entrained into the atmospheric boundary layer.
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Davrinche, Cécile, Anaïs Orsi, Cécile Agosta, Charles Amory, and Christoph Kittel. "Understanding the drivers of near-surface winds in Adélie Land, East Antarctica." Cryosphere 18, no. 5 (2024): 2239–56. http://dx.doi.org/10.5194/tc-18-2239-2024.
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Abstract. Near-surface winds play a crucial role in the climate of Antarctica, but accurately quantifying and understanding their drivers is complex. They result from the contribution of two distinct families of drivers: the large-scale pressure gradient and surface-induced pressure gradients known as katabatic and thermal wind. The extrapolation of vertical potential temperature above the boundary layer down to the surface enables us to separate and quantify the contribution of these different pressure gradients in the momentum budget equations. Using this method applied to outputs of the regional atmospheric model MAR at a 3-hourly resolution, we find that the seasonal and spatial variability in near-surface winds in Adélie Land is dominated by surface processes. On the other hand, high-frequency temporal variability (3-hourly) is mainly controlled by large-scale variability everywhere in Antarctica, except on the coast. In coastal regions, although the katabatic acceleration surpasses all other accelerations in magnitude, none of the katabatic or large-scale accelerations can be identified as the single primary driver of near-surface wind variability. The angle between the large-scale acceleration and the surface slope is a key factor in explaining strong wind speed events: the highest-wind-speed events happen when the katabatic and large-scale forcing are aligned, although each acceleration, when acting alone, can also cause strong wind speed. This study underlines the complexity of the drivers of Antarctic surface winds and the value of the momentum budget decomposition to identify drivers at different spatial and temporal scales.
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Caton Harrison, Thomas, Stavroula Biri, Thomas J. Bracegirdle, et al. "Reanalysis representation of low-level winds in the Antarctic near-coastal region." Weather and Climate Dynamics 3, no. 4 (2022): 1415–37. http://dx.doi.org/10.5194/wcd-3-1415-2022.
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Abstract. Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, and the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here, we investigate the representation of the mean state and short-term variability of coastal easterlies in three recent reanalyses, ERA5, MERRA-2 and JRA-55. Reanalysed winds are compared with summertime marine near-surface wind observations from the Advanced Scatterometer (ASCAT) and surface and upper air measurements from coastal stations. Reanalysis coastal easterlies correlate highly with ASCAT (r= 0.91, 0.89 and 0.85 for ERA5, MERRA-2 and JRA-55, respectively) but notable wind speed biases are found close to the coastal margins, especially near complex orography and at high wind speeds. To characterise short-term variability, 12-hourly reanalysis and coastal station winds are composited using self-organising maps (SOMs), which cluster timesteps under similar synoptic and mesoscale influences. Reanalysis performance is sensitive to the flow configuration at stations near steep coastal slopes, where they fail to capture the magnitude of near-surface wind speed variability when synoptic forcing is weak and conditions favour katabatic forcing. ERA5 exhibits the best overall performance, has more realistic orography, and a more realistic jet structure and temperature profile. These results demonstrate the regime behaviour of Antarctica's coastal winds and indicate important features of the coastal winds which are not well characterised by reanalysis datasets.
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LAL, R. P., and SURESH RAM. "Climatology of blizzards over Schirmacher Oasis, east Antarctica." MAUSAM 60, no. 1 (2021): 39–50. http://dx.doi.org/10.54302/mausam.v60i1.960.
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Weather in Antarctica is subject to frequent and sudden changes. Strong winds and blizzards dominate Antarctic weather. A combination of blowing snow, gale force wind and very low visibility is normally defined as blizzard. Meteorological data recorded at Indian Antarctic Station Maitri, in respect of blizzards recorded during the period 1990-2005 has been studied to find out climatological features of blizzards affecting Schirmacher Oasis.
 
 At Maitri the blizzard is mostly associated with extra-tropical storms and is normally preceded by precipitation. On average during the year about 21 blizzards affects the station for 45 days during the year. During the month of April to August 3 to 4 blizzards affects the station. Maximum number of blizzards occurs in the month of August with about 7 blizzard days. Average wind speed recorded during the blizzard is about 52 kt but it exceeded 100 kt on several occasions. The duration may vary from hours to days with average of 25 hours. Longest duration of 168 hours was recorded in June 1997. There are about 12 such occasions when blizzard lasted more than 72 hours. No correlation has been found between maximum wind speed and temperature rise during blizzard and the speed is also not correlated with pressure departure during the period.
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Andersen, Dale T., Christopher P. McKay, and Victor Lagun. "Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica." Journal of Applied Meteorology and Climatology 54, no. 7 (2015): 1393–412. http://dx.doi.org/10.1175/jamc-d-14-0251.1.
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AbstractIn November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 ± 0.6 W m−2. The mean annual temperature at Lake Untersee was determined to be −10.6° ± 0.6°C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were −3.5°, −1.9°, −2.2°, −2.6°, and −2.5°C. The maximum (minimum) temperatures were +5.3°, +7.6°, +5.7°, +4.4°, and +9.0°C (−13.8°, −12.8°, −12.9°, −13.5°, and −12.1°C). The average of the wind speed recorded was 5.4 m s−1, the maximum was 35.7 m s−1, and the average daily maximum was 15 m s−1. The wind speed was higher in the winter, averaging 6.4 m s−1. Summer winds averaged 4.7 m s−1. The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.
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Seefeldt, Mark W., John J. Cassano, and Thomas R. Parish. "Dominant Regimes of the Ross Ice Shelf Surface Wind Field during Austral Autumn 2005." Journal of Applied Meteorology and Climatology 46, no. 11 (2007): 1933–55. http://dx.doi.org/10.1175/2007jamc1442.1.
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Abstract An analysis of the surface wind field across the Ross Ice Shelf, Antarctica, is conducted for austral autumn 2005. The airflow is divided into dominant wind regimes identifying similar wind patterns and the associated typical atmospheric forcing. The results of previous research and a seasonal analysis of the recently expanded network of automatic weather stations in the Ross Ice Shelf region are used to define the dominant wind regimes. Events composing each wind regime are identified by matching wind speed and wind direction observations at several automatic weather station sites for durations of at least 10 h. The four different dominant wind regimes are barrier wind, strong katabatic, weak katabatic, and light wind. Each wind regime is studied through the use of wind rose plots and sea level pressure fields from the Antarctic Mesoscale Prediction System. The sea level pressure fields are used to characterize the forcing of the surface wind field by synoptic pressure gradients. The four dominant wind regimes result in classifying less than 50% of the total hours for austral autumn 2005. The results indicate that previous studies of the Ross Ice Shelf surface wind field, focusing on katabatic winds and barrier winds, represent less than one-half of the observed winds. This study provides a better understanding of the composition of the surface wind field in Antarctica and more insight into the characteristics of the Ross Ice Shelf airstream.
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Wenta, Marta, and John J. Cassano. "The Atmospheric Boundary Layer and Surface Conditions during Katabatic Wind Events over the Terra Nova Bay Polynya." Remote Sensing 12, no. 24 (2020): 4160. http://dx.doi.org/10.3390/rs12244160.
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Off the coast of Victoria Land, Antarctica an area of open water—the Terra Nova Bay Polynya (TNBP)—persists throughout the austral winter. The development of this coastal polynya is driven by extreme katabatic winds blowing down the slopes of Transantarctic Mountains. The surface-atmosphere coupling and ABL transformation during the katabatic wind events between 18 and 25 September 2012 in Terra Nova Bay are studied, using observations from Aerosonde unmanned aircraft system (UAS), numerical modeling results and Antarctic Weather Station (AWS) measurements. First, we analyze how the persistence and strength of the katabatic winds relate to sea level pressure (SLP) changes in the region throughout the studied period. Secondly, the polynya extent variations are analysed in relation to wind speed changes. We conclude that the intensity of the flow, surface conditions in the bay and regional SLP fluctuations are all interconnected and contribute to polynya development. We also analyse the Antarctic Mesoscale Prediction System (AMPS) forecast for the studied period and find out that incorrect representation of vertical ABL properties over the TNBP might be caused by overestimated sea ice concentrations (SIC) used as model input. Altogether, this research provides a unique description of TNBP development and its interactions with the atmosphere and katabatic winds.
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Nigro, Melissa A., John J. Cassano, Matthew A. Lazzara, and Linda M. Keller. "Case Study of a Barrier Wind Corner Jet off the Coast of the Prince Olav Mountains, Antarctica." Monthly Weather Review 140, no. 7 (2012): 2044–63. http://dx.doi.org/10.1175/mwr-d-11-00261.1.
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Abstract The Ross Ice Shelf airstream (RAS) is a barrier parallel flow along the base of the Transantarctic Mountains. Previous research has hypothesized that a combination of katabatic flow, barrier winds, and mesoscale and synoptic-scale cyclones drive the RAS. Within the RAS, an area of maximum wind speed is located to the northwest of the protruding Prince Olav Mountains. In this region, the Sabrina automatic weather station (AWS) observed a September 2009 high wind event with wind speeds in excess of 20 m s−1 for nearly 35 h. The following case study uses in situ AWS observations and output from the Antarctic Mesoscale Prediction System to demonstrate that the strong wind speeds during this event were caused by a combination of various forcing mechanisms, including katabatic winds, barrier winds, a surface mesocyclone over the Ross Ice Shelf, an upper-level ridge over the southern tip of the Ross Ice Shelf, and topographic influences from the Prince Olav Mountains. These forcing mechanisms induced a barrier wind corner jet to the northwest of the Prince Olav Mountains, explaining the maximum wind speeds observed in this region. The RAS wind speeds were strong enough to induce two additional barrier wind corner jets to the northwest of the Prince Olav Mountains, resulting in a triple barrier wind corner jet along the base of the Transantarctic Mountains.
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Yang, Qike, Xiaoqing Wu, Xiaodan Hu, et al. "Antarctic atmospheric Richardson number from radiosonde measurements and AMPS." Atmospheric Chemistry and Physics 23, no. 11 (2023): 6339–55. http://dx.doi.org/10.5194/acp-23-6339-2023.
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Abstract. Monitoring a wide range of atmospheric turbulence over the Antarctic continent is still tricky, while the atmospheric Richardson number (Ri; a valuable parameter which determines the possibility that turbulence could be triggered) is easier to obtain. The Antarctic atmospheric Ri, calculated from the potential temperature and wind speed, was investigated using the daily results from the radiosoundings and forecasts of the Antarctic Mesoscale Prediction System (AMPS). Radiosoundings for a year at three sites (McMurdo – MM, South Pole – SP, and Dome C – DC) were used to quantify the reliability of the AMPS forecasts. The AMPS-forecasted Ri can identify the main spatiotemporal characteristics of atmospheric turbulence over the Antarctic region. The correlation coefficients (Rxy) of log 10(Ri) at McMurdo, the South Pole, and Dome C are 0.71, 0.59, and 0.53, respectively. The Ri was generally underestimated by the AMPS and the AMPS could better capture the trend of log 10(Ri) at relatively unstable atmospheric conditions. The seasonal median of log 10(Ri) along two vertical cross-sections of the AMPS forecasts are presented, and it shows some zones where atmospheric turbulence can be highly triggered in Antarctica. The Ri distributions appear to be reasonably correlated to some large-scale phenomena or local-scale dynamics (katabatic winds, polar vortices, convection, gravity wave, etc.) over the Antarctic plateau and surrounding ocean. Finally, the log 10(Ri) at the planetary boundary layer height (PBLH) were calculated and their median value is 0.316. This median value, in turn, was used to estimate the PBLH and agrees well with the AMPS-forecasted PBLH (Rxy>0.69). Overall, our results suggest that the Ri estimated by AMPS are reasonable and the turbulence conditions in Antarctica are well revealed.
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Liston, Glen E., Jan-Gunnar Winther, Oddbjørn Bruland, Hallgeir Elvehøy, Knut Sand, and Lars Karlöf. "Snow and blue-ice distribution patterns on the coastal Antarctic Ice Sheet." Antarctic Science 12, no. 1 (2000): 69–79. http://dx.doi.org/10.1017/s0954102000000109.
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Surface patterns of alternating snow and blue-ice bands are found in the Jutulgryta area of Dronning Maud Land, Antarctica. The snow-accumulation regions exist in the lee of blue-ice topographic ridges aligned perpendicular to winter winds. The snow bands are c. 500–2000 m wide and up to several kilometres long. In Jutulgryta, these features cover c. 5000 km2. These alternating snow and blue-ice bands are simulated using a snow transport and redistribution model, SnowTran-3D, that is driven with a winter cycle of observed daily screen-height air temperature, humidity, and wind speed and direction. The snow-transport model is coupled to a wind model that simulates wind flow over the relatively complex topography. Model results indicate that winter winds interact with the ice topographic features to produce alternating surface patterns of snow accumulation and erosion. In addition, model sensitivity simulations suggest that subtle topographic variations, on the order of 5m elevation change over a horizontal distance of 1 to 1.5 km, can lead to snow-accumulation variations that differ by a factor of six. This result is expected to have important consequences regarding the choice of sites for ice-coring efforts in Antarctica and elsewhere.
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Bageston, J. V., C. M. Wrasse, P. P. Batista, et al. "Observation of a mesospheric front in a thermal-doppler duct over King George Island, Antarctica." Atmospheric Chemistry and Physics 11, no. 23 (2011): 12137–47. http://dx.doi.org/10.5194/acp-11-12137-2011.
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Abstract. A mesospheric front was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W), located on King George island on the Antarctic Peninsula. The observed wave propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68° S, 68° W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the wave event. A wavelet technique was applied to the wind in the plane of wave propagation at the OH emission height spanning three days centered on the front event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling mesospheric front propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the wave front event was supported by a duct including contributions from both winds and temperature.
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Franeker, Jan A. Van, Jeroen C. S. Creuwels, Willem Van Der Veer, Sam Cleland, and Graham Robertson. "Unexpected effects of climate change on the predation of Antarctic petrels." Antarctic Science 13, no. 4 (2001): 430–39. http://dx.doi.org/10.1017/s0954102001000591.
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Antarctic petrels Thalassoica antarctica on Ardery Island, Antarctica (66°S, 110°E), experienced major reductions in breeding success and breeder survival over four seasons between 1984/85 and 1996/97. In 1996 the reason was revealed. A large snowdrift covered part of the study colony on the cliffs. Southern giant petrels Macronectes giganteus, normally lacking access to this area, exploited the snow for soft ‘crash landings”. After landing they waited for the disturbed birds to resettle on their nests and then used surprise to seize and kill a victim. Predation continued into the egg period, and only stopped after the snowdrift had melted. Giant petrels showed no interest in the eggs but, during the panic caused by their activities, South Polar skuas Catharacta maccormicki took the deserted eggs. Antarctic petrel mortality due to predation within the 1996/97 season amounted to 15.4% of experienced breeders, and breeding success was reduced to virtually zero. Weather data from the nearby Casey station over the 1980–96 period showed that a significant increase in precipitation has occurred, in combination with shifts in speed and direction of winds. We conclude that the decreases in breeding success and survival in earlier seasons were also related to increased snowfall and predation. Although similar predation behaviour by giant petrels has not been reported before, we think that it is long established and explains why nesting of the smaller fulmarine petrels is limited to steeper cliffs or sheltered sites. The complexity of the response seems unlikely to be predicted by our present understanding of how climate change affects ecosystems.
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Allison, Ian. "Surface climate of the interior of the Lambert Glacier basin, Antarctica, from automatic weather station data." Annals of Glaciology 27 (1998): 515–20. http://dx.doi.org/10.3189/1998aog27-1-515-520.
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Data from six automatic weather stations deployed around the interior of the Lambert Glacier basin, Antarctica, at surface elevations of 1830-2741 m are used to compile a surface climatology of this part of interior Antarctica for the period 1994-96. The stations measure air pressure, near-surface wind speed and air temperature at several levels, wind direction and firn temperatures. The topography of the basin, which extends more than 800 km inland, controls the katabatic wind regime and strongly influences the surface climate of the region. Windiest sites are on the steep coastal slopes, and within the depression of the Lambert and Mellor Ice Streams where the flow is topographically channelled. Surface winds here show greater seasonal variation in speed but less variation in direction than elsewhere. The annual mean temperatures on the relatively steep slopes on the eastern side of the basin are 4-5°C warmer than at equivalent altitude on the western side. During winter, near-synchronous synoptic temperature and pressure increases occur throughout the basin to at least 1000 km from the coast. There is a consistent pattern of diurnal wind variation in the summer at all stations, with maximum wind speed at about 0900 LST (local solar time), and the most easterly direction at 1300 LST.
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Van Den Broeke, Michiel, and Richard Bintanja. "The interaction of katabatic winds and the formation of blue-ice areas in East Antarctica." Journal of Glaciology 41, no. 138 (1995): 395–407. http://dx.doi.org/10.1017/s0022143000016269.
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AbstractBlue-ice areas (BIAs) are an extreme example of a local mass-balance gradient and are furthermore reasonably stable in time and space owing to local feed-back mechanisms. A meteorological experiment, performed in and around a blue-ice area in Dronning Maud Land. East Antarctica, showed that during drifting-snow conditions surface wind speed over the blue ice behind the mountain barrier is equal to that away from the mountains, when corrected for surface roughness and stability. This implies that use of diagnostic katabatic wind models to estimate divergence of drifting snow can be extended to the situation where nunataks are involved in preventing the drifting snow from passing, which is the case for most BIAs. A diagnostic model is tested for a two-dimensional profile in Terre Adélie. after which it is applied to entire East Antarctica. The present order-of-magnitude estimate shows that areas sensitive to blue-ice formation appear where precipitation is low and mean annual wind speed is high, i.e. in Dronning Maud Land and the drainage basin of Lambert Glacier. The results appeared to be especially sensitive to a change in inversion strength: a decrease in inversion strength weakens the katabatic flow, and thus the amount of snowdrift transport, reducing the area where BIAs can develop.
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Van Den Broeke, Michiel, and Richard Bintanja. "The interaction of katabatic winds and the formation of blue-ice areas in East Antarctica." Journal of Glaciology 41, no. 138 (1995): 395–407. http://dx.doi.org/10.3189/s0022143000016269.
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AbstractBlue-ice areas (BIAs) are an extreme example of a local mass-balance gradient and are furthermore reasonably stable in time and space owing to local feed-back mechanisms. A meteorological experiment, performed in and around a blue-ice area in Dronning Maud Land. East Antarctica, showed that during drifting-snow conditions surface wind speed over the blue ice behind the mountain barrier is equal to that away from the mountains, when corrected for surface roughness and stability. This implies that use of diagnostic katabatic wind models to estimate divergence of drifting snow can be extended to the situation where nunataks are involved in preventing the drifting snow from passing, which is the case for most BIAs. A diagnostic model is tested for a two-dimensional profile in Terre Adélie. after which it is applied to entire East Antarctica. The present order-of-magnitude estimate shows that areas sensitive to blue-ice formation appear where precipitation is low and mean annual wind speed is high, i.e. in Dronning Maud Land and the drainage basin of Lambert Glacier. The results appeared to be especially sensitive to a change in inversion strength: a decrease in inversion strength weakens the katabatic flow, and thus the amount of snowdrift transport, reducing the area where BIAs can develop.
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Dice, Mckenzie J., John J. Cassano, and Gina C. Jozef. "Forcing for varying boundary layer stability across Antarctica." Weather and Climate Dynamics 5, no. 1 (2024): 369–94. http://dx.doi.org/10.5194/wcd-5-369-2024.
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Abstract. The relative importance of changes in radiative forcing (downwelling longwave radiation) and mechanical mixing (20 m wind speed) in controlling boundary layer stability annually and seasonally at five study sites across the Antarctica continent is presented. From near neutral to extremely strong near-surface stability, radiative forcing decreases with increasing stability, as expected, and is shown to be a major driving force behind variations in near-surface stability at all five sites. Mechanical mixing usually decreases with increasing near-surface stability for regimes with weak to extremely strong stability. For the cases where near neutral, very shallow mixed, and weak stability occur, the wind speed in the very shallow mixed case is usually weaker compared to the near neutral and weak stability cases, while radiative forcing is largest for the near neutral cases. This finding is an important distinguishing factor for the unique case where a very shallow mixed layer is present, indicating that weaker mechanical mixing in this case is likely responsible for the shallower boundary layer that defines the very shallow mixed stability regime. For cases with enhanced stability above a layer of weaker near-surface stability, lower downwelling longwave radiation promotes the persistence of the stronger stability aloft, while stronger near-surface winds act to maintain weaker stability immediately near the surface, resulting in this two-layer boundary layer stability regime.
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Champollion, N., G. Picard, L. Arnaud, E. Lefebvre, and M. Fily. "Hoar crystal development and disappearance at Dome C, Antarctica: observation by near-infrared photography and passive microwave satellite." Cryosphere Discussions 7, no. 1 (2013): 175–217. http://dx.doi.org/10.5194/tcd-7-175-2013.
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Abstract. Hoar crystals episodically cover the snow surface in Antarctica and affect the roughness and reflective properties of the air-snow interface. However, little is known about their evolution and the processes responsible for their development and disappearance despite a probable influence on the surface mass balance and energy budget. To investigate hoar evolution, we use continuous observations of the surface by in-situ near-infrared photography and by passive microwave remote sensing at Dome C in Antarctica. From the photography data, we retrieved a daily indicator of the presence/absence of hoar crystals using a texture analysis algorithm. The analysis of this 2-yr long time series shows that Dome C surface is covered almost half of the time by hoar. The development of hoar crystals takes a few days and seems to occur whatever the meteorological conditions. In contrast, the disappearance of hoar is rapid (a few hours) and coincident with either strong winds or with moderate winds associated with a change in wind direction from Southwest (the prevailing direction) to Southeast. From the microwave satellite data, we computed the polarisation ratio (i.e. horizontal over vertical polarised brightness temperatures), an indicator known to be sensitive to hoar in Greenland. Photography data and microwave polarisation ratio are correlated, i.e. high values of polarisation ratio which theoretically correspond to low snow density values near the surface are associated with the presence of hoar crystals in the photography data. Satellite data over nearly ten years (2002–2011) confirm that a strong decrease of the polarisation ratio (i.e. signature of hoar disappearance) is associated with an increase of wind speed or a change in wind direction from the prevailing direction. The photography data provides, in addition, evidence of interactions between hoar and snowfall. Further adding the combined influence of wind speed and wind direction results in a complex picture of the snow-atmosphere interactions in Antarctica which deserves further quantification and modelling.
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Champollion, N., G. Picard, L. Arnaud, E. Lefebvre, and M. Fily. "Hoar crystal development and disappearance at Dome C, Antarctica: observation by near-infrared photography and passive microwave satellite." Cryosphere 7, no. 4 (2013): 1247–62. http://dx.doi.org/10.5194/tc-7-1247-2013.
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Abstract. Hoar crystals episodically cover the snow surface in Antarctica and affect the roughness and reflective properties of the air–snow interface. However, little is known about their evolution and the processes responsible for their development and disappearance despite a probable influence on the surface mass balance and energy budget. To investigate hoar evolution, we use continuous observations of the surface by in situ near-infrared photography and by passive microwave remote sensing at Dome C in Antarctica. From the photography data, we retrieved a daily indicator of the presence/absence of hoar crystals using a texture analysis algorithm. The analysis of this 2 yr long time series shows that Dome C surface is covered almost half of the time by hoar. The development of hoar crystals takes a few days and seems to occur whatever the meteorological conditions. In contrast, the disappearance of hoar is rapid (a few hours) and coincident with either strong winds or with moderate winds associated with a change in wind direction from southwest (the prevailing direction) to southeast. From the microwave satellite data, we computed the polarisation ratio (i.e. horizontal over vertical polarised brightness temperatures), an indicator known to be sensitive to hoar in Greenland. Photography data and microwave polarisation ratio are correlated, i.e. high values of polarisation ratio which theoretically correspond to low snow density values near the surface are associated with the presence of hoar crystals in the photography data. Satellite data over nearly ten years (2002–2011) confirm that a strong decrease of the polarisation ratio (i.e. signature of hoar disappearance) is associated with an increase of wind speed or a change in wind direction from the prevailing direction. The photography data provides, in addition, evidence of interactions between hoar and snowfall. Further adding the combined influence of wind speed and wind direction results in a complex picture of the snow–atmosphere interactions in Antarctica which deserves further quantification and modelling.
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Steinhoff, Daniel F., David H. Bromwich, Michelle Lambertson, Shelley L. Knuth, and Matthew A. Lazzara. "A Dynamical Investigation of the May 2004 McMurdo Antarctica Severe Wind Event Using AMPS*." Monthly Weather Review 136, no. 1 (2008): 7–26. http://dx.doi.org/10.1175/2007mwr1999.1.
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Abstract On 15–16 May 2004 a severe windstorm struck McMurdo, Antarctica. The Antarctic Mesoscale Prediction System (AMPS) is used, along with available observations, to analyze the storm. A synoptic-scale cyclone weakens as it propagates across the Ross Ice Shelf toward McMurdo. Flow associated with the cyclone initiates a barrier jet along the Transantarctic Mountains. Forcing terms from the horizontal equations of motion are computed in the barrier wind to show that the local time tendency and momentum advection terms are key components of the force balance. The barrier jet interacts with a preexisting near-surface radiation inversion over the Ross Ice Shelf to set up conditions favorable for the development of large-amplitude mountain waves, leading to a downslope windstorm in the Ross Island area. Hydraulic theory can explain the structure of the downslope windstorms, with amplification of the mountain waves possibly caused by wave-breaking events. The underestimation of AMPS wind speed at McMurdo is caused by the misplacement of a hydraulic jump downstream of the downslope windstorms. The dynamics associated with the cyclone, barrier jet, and downslope windstorms are analyzed to determine the role of each in development of the severe winds.
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Bageston, J. V., C. M. Wrasse, P. P. Batista, et al. "Observation of a mesospheric front in a dual duct over King George Island, Antarctica." Atmospheric Chemistry and Physics Discussions 11, no. 5 (2011): 16185–206. http://dx.doi.org/10.5194/acpd-11-16185-2011.
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Abstract. A mesospheric bore was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W), located on King George island on the Antarctic Peninsula. The observed bore propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. There was no evidence of dissipation during its propagation within the field of view. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68° S, 68° W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the bore. A wavelet technique was applied to the wind in the plane of bore propagation at the OH emission height spanning three days centered on the bore event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling bore propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the bore was supported by a duct including contributions from both winds and temperature (or stability). A co-located airglow temperature imager operated simultaneously with the all-sky imager confirmed that the bore event was the dominant small-scale wave event during the analysis interval.
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Weber, Nicholas J., Matthew A. Lazzara, Linda M. Keller, and John J. Cassano. "The Extreme Wind Events in the Ross Island Region of Antarctica." Weather and Forecasting 31, no. 3 (2016): 985–1000. http://dx.doi.org/10.1175/waf-d-15-0125.1.
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Abstract Numerous incidents of structural damage at the U.S. Antarctic Program’s (USAP) McMurdo Station due to extreme wind events (EWEs) have been reported over the past decade. Utilizing nearly 20 yr (~1992–2013) of University of Wisconsin automatic weather station (AWS) data from three different stations in the Ross Island region (Pegasus North, Pegasus South, and Willie Field), statistical analysis shows no significant trends in EWE frequency, intensity, or duration. EWEs more frequently occur during the transition seasons. To assess the dynamical environment of these EWEs, Antarctic Mesoscale Prediction System (AMPS) forecast back trajectories are computed and analyzed in conjunction with several other AMPS fields for the strongest events at McMurdo Station. The synoptic analysis reveals that McMurdo Station EWEs are nearly always associated with strong southerly flow due to an approaching Ross Sea cyclone and an upper-level trough around Cape Adare. A Ross Ice Shelf air stream (RAS) environment is created with enhanced barrier winds along the Transantarctic Mountains, downslope winds in the lee of the glaciers and local topography, and a tip jet effect around Ross Island. The position and intensity of these Ross Sea cyclones are most influenced by the occurrence of a central Pacific ENSO event, which causes the upper-level trough to move westward. An approaching surface cyclone would then be in position to trigger an event, depending on how the wind direction and speed impinges on the complex topography around McMurdo Station.
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Genthon, Christophe, Dana Veron, Etienne Vignon, et al. "10 years of temperature and wind observation on a 45 m tower at Dome C, East Antarctic plateau." Earth System Science Data 13, no. 12 (2021): 5731–46. http://dx.doi.org/10.5194/essd-13-5731-2021.
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Abstract. Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the East Antarctic plateau. In the article, we present and analyze 10 years of data from six levels of meteorological instrumentation mounted on a 42 m tower located at Dome C, East Antarctica, near the Concordia research station, producing a unique climatology of the near-surface atmospheric environment (Genthon et al., 2021a, b). Monthly temperature and wind data demonstrate the large seasonal differences in the near-surface boundary layer dynamics, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer, leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual timescales. Analysis of observational uncertainty and comparison to reanalysis data from the latest generation of ECMWF (European Centre for Medium-Range Weather Forecasts) reanalyses (ERA5) indicate that wind speed is particularly difficult to measure at this location. Data are distributed on the PANGAEA data repository at https://doi.org/10.1594/PANGAEA.932512 (Genthon et al., 2021a) and https://doi.org/10.1594/PANGAEA.932513 (Genthon et al., 2021b).
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Ardon-Dryer, K., Z. Levin, and R. P. Lawson. "Characteristics of immersion freezing nuclei at the south pole station in Antarctica." Atmospheric Chemistry and Physics Discussions 11, no. 1 (2011): 91–120. http://dx.doi.org/10.5194/acpd-11-91-2011.
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Abstract. The effectiveness of aerosols as immersion freezing nuclei at the South Pole station was investigated during January and February 2009 using the FRIDGE-TAU. The analysis consisted of testing the freezing temperature of about 100–130 drops per sample containing aerosols collected at ground level and on a balloon lifted to different heights. All the drops froze between −18 °C and −27 °C. The temperature in which 50% of the drops froze occurred at −24 °C, while nuclei concentration of 1 L−1 at −22 °C was calculated. Meteorological conditions such as wind speed, ice precipitation as well as the trajectories of the air masses affected the ice nuclei concentrations. Higher concentrations were observed on days when the winds were stronger or when the air mass originated from the sea.
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Ardon-Dryer, K., Z. Levin, and R. P. Lawson. "Characteristics of immersion freezing nuclei at the South Pole station in Antarctica." Atmospheric Chemistry and Physics 11, no. 8 (2011): 4015–24. http://dx.doi.org/10.5194/acp-11-4015-2011.
Full textAbstract:
Abstract. The effectiveness of aerosols as immersion freezing nuclei at the South Pole station was investigated during January and February 2009 using the FRIDGE-TAU. The analysis consisted of testing the freezing temperature of about 100–130 drops per sample containing aerosols collected at ground level and on a balloon lifted to different heights. All the drops froze between −18 °C and −27 °C. The temperature in which 50 % of the drops froze occurred at −24 °C, while nuclei concentration of 1 L−1 at −23 °C was calculated. Meteorological conditions such as wind speed, ice precipitation as well as the trajectories of the air masses affected the ice nuclei concentrations. Higher concentrations were observed on days when the winds were stronger or when the air mass originated from the sea.
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Koffman, B. G., K. J. Kreutz, D. J. Breton, et al. "Centennial-scale variability of the Southern Hemisphere westerly wind belt in the eastern Pacific over the past two millennia." Climate of the Past 10, no. 3 (2014): 1125–44. http://dx.doi.org/10.5194/cp-10-1125-2014.
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Abstract. We present the first high-resolution (sub-annual) dust particle data set from West Antarctica, developed from the West Antarctic Ice Sheet (WAIS) Divide deep ice core (79.468° S, 112.086° W), and use it to reconstruct changes in atmospheric circulation over the past 2400 years. We find a background dust flux of ~4 mg m−2 year−1 and a mode particle size of 5–8 μm diameter. Through comparing the WAIS Divide record with other Antarctic ice core particle records, we observe that coastal and lower-elevation sites have higher dust fluxes and coarser particle size distributions (PSDs) than sites on the East Antarctic plateau, suggesting input from local dust sources at these lower-elevation sites. In order to explore the use of the WAIS Divide dust PSD as a proxy for past atmospheric circulation, we make quantitative comparisons between both mid-latitude zonal wind speed and West Antarctic meridional wind speed and the dust size record, finding significant positive interannual relationships. We find that the dust PSD is related to mid-latitude zonal wind speed via cyclonic activity in the Amundsen Sea region. Using our PSD record, and through comparison with spatially distributed climate reconstructions from the Southern Hemisphere (SH) middle and high latitudes, we infer that the SH westerlies occupied a more southerly position from circa 1050 to 1400 CE (Common Era), coinciding with the Medieval Climate Anomaly (MCA). Subsequently, at ca. 1430 CE, the wind belt shifted equatorward, where it remained until the mid-to-late twentieth century. We find covariability between reconstructions of El Niño–Southern Oscillation (ENSO) and the mid-latitude westerly winds in the eastern Pacific, suggesting that centennial-scale circulation changes in this region are strongly influenced by the tropical Pacific. Further, we observe increased coarse particle deposition over the past 50 years, consistent with observations that the SH westerlies have been shifting southward and intensifying in recent decades.
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Ma, Yongfeng, Lingen Bian, Cunde Xiao, Ian Allison, and Xiuji Zhou. "Near surface climate of the traverse route from Zhongshan Station to Dome A, East Antarctica." Antarctic Science 22, no. 4 (2010): 443–59. http://dx.doi.org/10.1017/s0954102010000209.
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AbstractSeasonal variation of temperature, pressure, snow accumulation, winds, and their harmonic analysis are presented by using the data from Zhongshan Station and three Automatic Weather Stations deployed between the East Antarctic coast and the summit of the ice sheet at Dome A for the period 2005–07. Results show that: 1) temperature, snow accumulation and specific humidity decrease with increasing elevation and distance from the coast, with snow accumulation decreasing from 199 mm water equivalent (w.e.) yr-1 at LGB69 (180 km from the coast) to 31 mm w.e. yr-1 at Dome A, 2) Dome A experiences an extremely low minimum temperature of -82.5°C with the monthly mean temperature below -50°C for eight months in contrast to Zhongshan Station which does not show any monthly mean temperatures below -20°C, 3) mean surface wind speed increases from the coast to the escarpment region, and then reduces rapidly towards the interior plateau with the strongest winds occurring at katabatic sites with the greatest surface slopes, 4) temperature and pressure all shows a distinct biannual oscillation with a main minimum in spring and a secondary minimum in autumn, differing slightly from station to station, and 5) winter temperature corelessness increases as a function of elevation and distance from the coast, from 0.260 at the coastal Zhongshan Station to 0.433 at Dome A.
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Wille, Jonathan D., David H. Bromwich, Melissa A. Nigro, et al. "Evaluation of the AMPS Boundary Layer Simulations on the Ross Ice Shelf with Tower Observations." Journal of Applied Meteorology and Climatology 55, no. 11 (2016): 2349–67. http://dx.doi.org/10.1175/jamc-d-16-0032.1.
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AbstractFlight operations in Antarctica rely on accurate weather forecasts aided by the numerical predictions primarily produced by the Antarctic Mesoscale Prediction System (AMPS) that employs the polar version of the Weather Research and Forecasting (Polar WRF) Model. To improve the performance of the model’s Mellor–Yamada–Janjić (MYJ) planetary boundary layer (PBL) scheme, this study examines 1.5 yr of meteorological data provided by the 30-m Alexander Tall Tower! (ATT) automatic weather station on the western Ross Ice Shelf from March 2011 to July 2012. Processed ATT observations at 10-min intervals from the multiple observational levels are compared with the 5-km-resolution AMPS forecasts run daily at 0000 and 1200 UTC. The ATT comparison shows that AMPS has fundamental issues with moisture and handling stability as a function of wind speed. AMPS has a 10-percentage-point (i.e., RH unit) relative humidity dry bias year-round that is highest when katabatic winds from the Byrd and Mulock Glaciers exceed 15 m s−1. This is likely due to nonlocal effects such as errors in the moisture content of the katabatic flow and AMPS not parameterizing the sublimation from blowing snow. AMPS consistently overestimates the wind speed at the ATT by 1–2 m s−1, in agreement with previous studies that attribute the high wind speed bias to the MYJ scheme. This leads to reduced stability in the simulated PBL, thus affecting the model’s ability to properly simulate the transfer of heat and momentum throughout the PBL.
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Jonsson, Stig. "Synoptic forcing of wind and temperature in a large cirque 300 km from the coast of East Antarctica." Antarctic Science 7, no. 4 (1995): 409–20. http://dx.doi.org/10.1017/s0954102095000575.
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Between 18 January 1988 and 3 June 1989, an automatic weather station recorded 13 different weather parameters every 3 h on a blue-ice area located in Scharffenbergbotnen, a large cirque in central Heimefrontfjella 300 km from the Weddell Sea coast. The first part of the paper reports on annual and monthly data regarding air temperature, air pressure, wind speed and wind direction, and a comparison is also made with corresponding data from the Neumayer and Halley stations. The second part deals mainly with winter (i.e. April–September) conditions in Scharffenbergbotnen. They seem, at least during 1988–89, to have been characterized by a large-scale (30–40 days) and, superimposed on the large-scale, a small-scale (3–4 days) co-variation of air temperature, air pressure and wind speed. The large-scale variation was earlier found to be synoptically forced. This paper shows that synoptic forcing exists also on smaller time scales. Pools of cold, stagnant air are regularly formed in the cirque only to be blown away by katabatic winds triggered by small variations in the synoptic pressure field. When this happens the air temperature increases by more than 20°C and the wind direction swings from east towards south-east. When low pressures dominate in the eastern part of the Weddell Sea, the katabatic winds become very strong, but weaker wind pulses also take place when the synoptic pressure gradient is directed towards the north-east. It therefore seems as if these very regular katabatic events are forced both by synoptic-scale pressure gradients and gradients due to the sloped inversion.
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Thompson, Lisa, Madison Smith, Jim Thomson, Sharon Stammerjohn, Steve Ackley, and Brice Loose. "Frazil ice growth and production during katabatic wind events in the Ross Sea, Antarctica." Cryosphere 14, no. 10 (2020): 3329–47. http://dx.doi.org/10.5194/tc-14-3329-2020.
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Abstract. Katabatic winds in coastal polynyas expose the ocean to extreme heat loss, causing intense sea ice production and dense water formation around Antarctica throughout autumn and winter. The advancing sea ice pack, combined with high winds and low temperatures, has limited surface ocean observations of polynyas in winter, thereby impeding new insights into the evolution of these ice factories through the dark austral months. Here, we describe oceanic observations during multiple katabatic wind events during May 2017 in the Terra Nova Bay and Ross Sea polynyas. Wind speeds regularly exceeded 20 m s−1, air temperatures were below −25 ∘C, and the oceanic mixed layer extended to 600 m. During these events, conductivity–temperature–depth (CTD) profiles revealed bulges of warm, salty water directly beneath the ocean surface and extending downwards tens of meters. These profiles reflect latent heat and salt release during unconsolidated frazil ice production, driven by atmospheric heat loss, a process that has rarely if ever been observed outside the laboratory. A simple salt budget suggests these anomalies reflect in situ frazil ice concentration that ranges from 13 to 266×10-3 kg m−3. Contemporaneous estimates of vertical mixing reveal rapid convection in these unstable density profiles and mixing lifetimes from 7 to 12 min. The individual estimates of ice production from the salt budget reveal the intensity of short-term ice production, up to 110 cm d−1 during the windiest events, and a seasonal average of 29 cm d−1. We further found that frazil ice production rates covary with wind speed and with location along the upstream–downstream length of the polynya. These measurements reveal that it is possible to indirectly observe and estimate the process of unconsolidated ice production in polynyas by measuring upper-ocean water column profiles. These vigorous ice production rates suggest frazil ice may be an important component in total polynya ice production.
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Frankinet, Baptiste, Thomas Lecocq, and Thierry Camelbeeck. "Wind-induced seismic noise at the Princess Elisabeth Antarctica Station." Cryosphere 15, no. 10 (2021): 5007–16. http://dx.doi.org/10.5194/tc-15-5007-2021.
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Abstract. Icequakes are the result of processes occurring within the ice mass or between the ice and its environment. Studying icequakes provides a unique view on ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental or climate changes are reflected in icequakes. Counting and characterizing icequakes is thus essential to monitor them. Most of the icequakes recorded by the seismic station at the Belgian Princess Elisabeth Antarctica Station (PE) have small amplitudes corresponding to maximal displacements of a few nanometres. Their detection threshold is highly variable because of the rapid and strong changes in the local seismic noise level. Therefore, we evaluated the influence of katabatic winds on the noise measured by the well-protected PE surface seismometer. Our purpose is to identify whether the lack of icequake detection during some periods could be associated with variations in the processes generating them or simply with a stronger seismic noise linked to stronger wind conditions. We observed that the wind mainly influences seismic noise at frequencies greater than 1 Hz. The seismic noise power exhibits a bilinear correlation with the wind velocity, with two different slopes at a wind velocity lower and greater than 6 m s−1 and with, for example at a period of 0.26 s, a respective variation of 0.4 dB (m −1 s) and 1.4 dB (m −1 s). These results allowed a synthetic frequency and wind-speed-dependent noise model to be presented that explains the behaviour of the wind-induced seismic noise at PE, which shows that seismic noise amplitude increases exponentially with increasing wind speed. This model enables us to study the influence of the wind on the original seismic dataset, which improves the observation of cryoseismic activity near the PE station.
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Thiery, W., I. V. Gorodetskaya, R. Bintanja, et al. "Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica." Cryosphere Discussions 6, no. 2 (2012): 1491–530. http://dx.doi.org/10.5194/tcd-6-1491-2012.
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Abstract. In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance. Comparison to three other AWSs in Dronning Maud Land shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10–23 % of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (18 mm w.e. yr–1 compared to 42 mm w.e. yr–1 at Svea Cross and 52 mm w.e. yr–1 at Wasa/Aboa). This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and therefore on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. These wind speed classes turn out to contribute most to the total snowdrift sublimation mass flux, given their ability to lift a high number of particles while still allowing for considerable undersaturation.
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Keenan, Eric, Nander Wever, Jan T. M. Lenaerts, and Brooke Medley. "A wind-driven snow redistribution module for Alpine3D v3.3.0: adaptations designed for downscaling ice sheet surface mass balance." Geoscientific Model Development 16, no. 11 (2023): 3203–19. http://dx.doi.org/10.5194/gmd-16-3203-2023.
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Abstract. Ice sheet surface mass balance describes the net snow accumulation at the ice sheet surface. On the Antarctic ice sheet, winds redistribute snow, resulting in a surface mass balance that is variable in both space and time. Representing wind-driven snow redistribution processes in models is critical for local assessments of surface mass balance, repeat altimetry studies, and interpretation of ice core accumulation records. To this end, we have adapted Alpine3D, an existing distributed snow modeling framework, to downscale Antarctic surface mass balance to horizontal resolutions up to 1 km. In particular, we have introduced a new two-dimensional advection-based wind-driven snow redistribution module that is driven by an offline coupling between WindNinja, a wind downscaling model, and Alpine3D. We then show that large accumulation variability can be at least partially explained by terrain-induced wind speed variations which subsequently redistribute snow around rolling topography. By comparing Alpine3D to airborne-derived snow accumulation measurements within a testing domain over Pine Island Glacier in West Antarctica, we demonstrate that our Alpine3D downscaling approach improves surface mass balance estimates when compared to the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), a global atmospheric reanalysis which we use as atmospheric forcing. In particular, when compared to MERRA-2, Alpine3D reduces simulated surface mass balance root mean squared error by 23.4 mmw.e.yr-1 (13 %) and increases variance explained by 24 %. Despite these improvements, our results demonstrate that considerable uncertainty stems from the employed saltation model, confounding simulations of surface mass balance variability.
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van den Broeke, Michiel R., Jan-Gunnar Winther, Elisabeth Isaksson, et al. "Climate variables along a traverse line in Dronning Maud Land, East Antarctica." Journal of Glaciology 45, no. 150 (1999): 295–302. http://dx.doi.org/10.3189/s0022143000001799.
Full textAbstract:
AbstractTemperature, density and accumulation data were obtained from shallow firn cores, drilled during an overland traverse through a previously unknown part of Dronning Maud Land, East Antarctica. The traverse area is characterised by high mountains that obstruct the ice flow, resulting in a sudden transition from the polar plateau to the coastal region. The spatial variations of potential temperature, near-surface firn density and accumulation suggest that katabatic winds are active in this region. Proxy wind data derived from firn-density profiles confirm that annual mean wind speed is strongly related to the magnitude of the surface slope. The high elevation of the ice sheet south of the mountains makes for a dry, cold climate, in which mass loss owing to sublimation is small and erosion of snow by the wind has a potentially large impact on the surface mass balance. A simple katabatic-wind model is used to explain the variations of accumulation along the traverse line in terms of divergence/convergence of the local transport of drifting snow. The resulting wind- and snowdrift patterns are closely connected to the topography of the ice sheet: ridges are especially sensitive to erosion, while ice streams and other depressions act as collectors of drifting snow.
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van den Broeke, Michiel R., Jan-Gunnar Winther, Elisabeth Isaksson, et al. "Climate variables along a traverse line in Dronning Maud Land, East Antarctica." Journal of Glaciology 45, no. 150 (1999): 295–302. http://dx.doi.org/10.1017/s0022143000001799.
Full textAbstract:
AbstractTemperature, density and accumulation data were obtained from shallow firn cores, drilled during an overland traverse through a previously unknown part of Dronning Maud Land, East Antarctica. The traverse area is characterised by high mountains that obstruct the ice flow, resulting in a sudden transition from the polar plateau to the coastal region. The spatial variations of potential temperature, near-surface firn density and accumulation suggest that katabatic winds are active in this region. Proxy wind data derived from firn-density profiles confirm that annual mean wind speed is strongly related to the magnitude of the surface slope. The high elevation of the ice sheet south of the mountains makes for a dry, cold climate, in which mass loss owing to sublimation is small and erosion of snow by the wind has a potentially large impact on the surface mass balance. A simple katabatic-wind model is used to explain the variations of accumulation along the traverse line in terms of divergence/convergence of the local transport of drifting snow. The resulting wind- and snowdrift patterns are closely connected to the topography of the ice sheet: ridges are especially sensitive to erosion, while ice streams and other depressions act as collectors of drifting snow.
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Thiery, W., I. V. Gorodetskaya, R. Bintanja, et al. "Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica." Cryosphere 6, no. 4 (2012): 841–57. http://dx.doi.org/10.5194/tc-6-841-2012.
Full textAbstract:
Abstract. In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance during 2009 and 2010. Comparison to three other AWSs in Dronning Maud Land with 11 to 13 yr of observations shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10–23% of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (17 mm w.e. yr−1 compared to 42 mm w.e. yr−1 at Svea Cross and 52 mm w.e. yr−1 at Wasa/Aboa). This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and, therefore, on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. This wind speed class turns out to contribute most to the total snowdrift sublimation mass flux, given its ability to lift a high number of particles while still allowing for considerable undersaturation.
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Reijmer, Carleen, Wouter Greuell, and Johannes Oerlemans. "The annual cycle of meteorological variables and the surface energy balance on Berkner Island, Antarctica." Annals of Glaciology 29 (1999): 49–54. http://dx.doi.org/10.3189/172756499781821166.
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AbstractIn February 1995 an automatic weather station (AWS) was placed on Thyssen Hohe, the south dome of Berkner Island, Antarctica. A fairly complete 3 year meteorological dataset of hourly average data was obtained. The mean annual temperature is about –24°C. The annual mass balance is about +180 mm we. Summer temperatures stay below 0°C, which implies that no melt takes place. Because the AWS is located on a dome, katabatic winds are not active, the wind direction is variable (directional constancy 0.38) and the wind speed relatively low (4.5 ms−1). Annual average variables are compared with data from Recovery Glacier AWS and Halley station.The measurements are used to evaluate the surface energy fluxes for the 3 year period by using a surface energy-balance model. The annual average gain of energy from the sensible-heat flux ( + 10.8 W m–2) is balanced by a negative net radiative flux (–9.1 W m−2) and a small negative latent-heat flux (-1.7 W rrT2). The annual subsurface flux is small.
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Vignon, Étienne, Ghislain Picard, Claudio Durán-Alarcón, Simon P. Alexander, Hubert Gallée, and Alexis Berne. "Gravity Wave Excitation during the Coastal Transition of an Extreme Katabatic Flow in Antarctica." Journal of the Atmospheric Sciences 77, no. 4 (2020): 1295–312. http://dx.doi.org/10.1175/jas-d-19-0264.1.
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Abstract The offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of polynyas. In this study, we make use of a combination of ground-based remotely sensed and meteorological measurements at Dumont d’Urville (DDU) station, satellite images, and simulations with the Weather Research and Forecasting Model to analyze a major katabatic wind event in Adélie Land. Once well developed over the slope of the ice sheet, the katabatic flow experiences an abrupt transition near the coastal edge consisting of a sharp increase in the boundary layer depth, a sudden decrease in wind speed, and a decrease in Froude number from 3.5 to 0.3. This so-called katabatic jump manifests as a turbulent “wall” of blowing snow in which updrafts exceed 5 m s−1. The wall reaches heights of 1000 m and its horizontal extent along the coast is more than 400 km. By destabilizing the boundary layer downstream, the jump favors the trapping of a gravity wave train—with a horizontal wavelength of 10.5 km—that develops in a few hours. The trapped gravity waves exert a drag that considerably slows down the low-level outflow. Moreover, atmospheric rotors form below the first wave crests. The wind speed record measured at DDU in 2017 (58.5 m s−1) is due to the vertical advection of momentum by a rotor. A statistical analysis of observations at DDU reveals that katabatic jumps and low-level trapped gravity waves occur frequently over coastal Adélie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics.
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Chenoli, Sheeba Nettukandy, John Turner, and Azizan Abu Samah. "A Strong Wind Event on the Ross Ice Shelf, Antarctica: A Case Study of Scale Interactions." Monthly Weather Review 143, no. 10 (2015): 4163–80. http://dx.doi.org/10.1175/mwr-d-15-0002.1.
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Abstract In situ observations, satellite imagery, numerical weather prediction, and reanalysis fields are used to investigate the synoptic and mesoscale environment of a strong wind event (SWE) at McMurdo Station/Ross Island region on the Ross Ice Shelf, Antarctica, on 10 October 2003. The SWE occurred during the passage of a sequence of three mesoscale low pressure systems from the central Ross Ice Shelf to the southwest Ross Sea. A potential vorticity (PV) analysis showed that the lows drew air of continental origin down the glacial valleys of the Transantarctic Mountains and onto the ice shelf as a katabatic drainage flow. However, the analysis indicated that the air mass associated with the SWE was of recurved maritime origin drawn in by the second mesoscale low (L2). This air mass approached McMurdo Station from the south where interactions with the orography played a critical role. In the early stages of the event, when the wind speed was less than 10 m s−1, the air was deflected around the topographical features, such as Minna Bluff and Black and White Islands. As the pressure gradient increased, winds of more than 10 m s−1 crossed the orography and developed mountain waves along the lee slopes. When the Froude number became larger than 1, large-amplitude vertically propagating mountain waves developed over the McMurdo Station/Ross Island area, increasing the wind to 16 m s−1. The reanalysis fields did not resolve the mesoscale lows; however, the Antarctic Mesoscale Prediction System (AMPS) model was able to simulate important characteristics of the SWE such as the mesoscale low pressure system, flow around the topographical barrier, and the mountain wave.
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Zwinger, T., T. Malm, M. Schäfer, R. Stenberg, and J. C. Moore. "Numerical simulations and observations of the role of katabatic winds in the creation and maintenance of Scharffenbergbotnen blue ice area, Antarctica." Cryosphere 9, no. 4 (2015): 1415–26. http://dx.doi.org/10.5194/tc-9-1415-2015.
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Abstract. We model the role of katabatic winds in the formation and maintenance of a blue ice area in Scharffenbergbotnen valley, Antarctica, using the finite element code Elmer. The high-horizontal-resolution (50–200 m) numerical simulations of the local wind flow from katabatic wind fronts show high spatial variability in wind-impact patterns and good congruence between places with high near-surface wind speeds and the blue ice area. In addition we perform wind simulations on an altered glacier geometry that resembles the thicker ice cover at the Late Glacial Maximum (LGM). These simulations indicate that the pronounced spatial wind-impact patterns depend on present-day geometry and did not occur during the LGM. This leads to the conclusion that the formation of the inner blue ice area of the Scharffenbergbotnen valley started only after the lowering of the ice surface, i.e. after the LGM. Experiments with smoothed surface topography suggest that detailed positions of the high wind regions, and hence individual blue ice fields, may have varied as the ice sheet lowered. The simulation results obtained with the present-day geometry were fortuitously confirmed by the destruction of a field camp located in a high-wind-speed area and its subsequent redistribution to low-velocity areas. The experiments and the field observations are consistent with localized violent katabatic events rather than synoptic-scale storms, playing the dominant role in the formation and maintenance of this and perhaps many blue ice areas.
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Monaghan, Andrew J., David H. Bromwich, Jordan G. Powers, and Kevin W. Manning. "The Climate of the McMurdo, Antarctica, Region as Represented by One Year of Forecasts from the Antarctic Mesoscale Prediction System*." Journal of Climate 18, no. 8 (2005): 1174–89. http://dx.doi.org/10.1175/jcli3336.1.
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Abstract In response to the need for improved weather prediction capabilities in support of the U.S. Antarctic Program’s Antarctic field operations, the Antarctic Mesoscale Prediction System (AMPS) was implemented in October 2000. AMPS employs a limited-area model, the Polar fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), optimized for use over ice sheets. Twice-daily forecasts from the 3.3-km resolution domain of AMPS are joined together to study the climate of the McMurdo region from June 2002 to May 2003. Annual and seasonal distributions of wind direction and speed, 2-m temperature, mean sea level pressure, precipitation, and cloud fraction are presented. This is the first time a model adapted for polar use and with relatively high resolution is used to study the climate of the rugged McMurdo region, allowing several important climatological features to be investigated with unprecedented detail. Orographic effects exert an important influence on the near-surface winds. Time-mean vortices occur in the lee of Ross Island, perhaps a factor in the high incidence of mesoscale cyclogenesis noted in this area. The near-surface temperature gradient is oriented northwest to southeast with the warmest temperatures in the northwest near McMurdo and the gradient being steepest in winter. The first-ever detailed precipitation maps of the region are presented. Orographic precipitation maxima occur on the southerly slopes of Ross Island and in the mountains to the southwest. The source of the moisture is primarily from the large synoptic systems passing to the northeast and east of Ross Island. A precipitation-shadow effect appears to be an important influence on the low precipitation amounts observed in the McMurdo Dry Valleys. Total cloud fraction primarily depends on the amount of open water in the Ross Sea; the cloudiest region is to the northeast of Ross Island in the vicinity of the Ross Sea polynya.
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Van de Wiel, Bas J. H., Etienne Vignon, Peter Baas, et al. "Regime Transitions in Near-Surface Temperature Inversions: A Conceptual Model." Journal of the Atmospheric Sciences 74, no. 4 (2017): 1057–73. http://dx.doi.org/10.1175/jas-d-16-0180.1.
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Abstract A conceptual model is used in combination with observational analysis to understand regime transitions of near-surface temperature inversions at night as well as in Arctic conditions. The model combines a surface energy budget with a bulk parameterization for turbulent heat transport. Energy fluxes or feedbacks due to soil and radiative heat transfer are accounted for by a “lumped parameter closure,” which represents the “coupling strength” of the system. Observations from Cabauw, Netherlands, and Dome C, Antarctica, are analyzed. As expected, inversions are weak for strong winds, whereas large inversions are found under weak-wind conditions. However, a sharp transition is found between those regimes, as it occurs within a narrow wind range. This results in a typical S-shaped dependency. The conceptual model explains why this characteristic must be a robust feature. Differences between the Cabauw and Dome C cases are explained from differences in coupling strength (being weaker in the Antarctic). For comparison, a realistic column model is run. As findings are similar to the simple model and the observational analysis, it suggests generality of the results. Theoretical analysis reveals that, in the transition zone near the critical wind speed, the response time of the system to perturbations becomes large. As resilience to perturbations becomes weaker, it may explain why, within this wind regime, an increase of scatter is found. Finally, the so-called heat flux duality paradox is analyzed. It is explained why numerical simulations with prescribed surface fluxes show a dynamical response different from more realistic surface-coupled systems.
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Butterworth, Brian J., and Scott D. Miller. "Automated Underway Eddy Covariance System for Air–Sea Momentum, Heat, and CO2 Fluxes in the Southern Ocean." Journal of Atmospheric and Oceanic Technology 33, no. 4 (2016): 635–52. http://dx.doi.org/10.1175/jtech-d-15-0156.1.
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AbstractA ruggedized closed-path eddy covariance (EC) system was designed for unattended direct measurements of air–sea momentum, heat, and CO2 flux, and was deployed on the Research Vessel Icebreaker (RV/IB) Nathaniel B. Palmer (NBP), an Antarctic research and supply vessel. The system operated for nine cruises during 18 months from January 2013 to June 2014 in the Southern Ocean and coastal Antarctica, sampling a wide variety of wind, wave, biological productivity, and ice conditions. The methods are described and the results are shown for two cruises chosen for their latitudinal range, inclusion of both open water and sea ice cover, and relatively large air–water CO2 concentration differences (ΔpCO2). Ship flow distortion was addressed by comparing mean winds, fluxes, and cospectra from an array of 3D anemometers at the NBP bow, comparing measured fluxes with bulk formulas, and implementing and evaluating several recently published data processing techniques. Quality-controlled momentum, heat, and CO2 flux data were obtained for 25% of the periods when NBP was at sea, with most (86%) of the rejected periods due to wind directions relative to the ship >±30° from the bow. In contrast to previous studies, no bias was apparent in measured CO2 fluxes for low |ΔpCO2|. The relationship between momentum flux and wind speed showed a clear dependence on the degree of sea ice cover, a result facilitated by the geographical coverage possible with a ship-based approach. These results indicate that ship-based unattended EC in high latitudes is feasible, and recommendations for deployments of underway systems in such environments are provided.
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Tastula, Esa-Matti, and Timo Vihma. "WRF Model Experiments on the Antarctic Atmosphere in Winter." Monthly Weather Review 139, no. 4 (2011): 1279–91. http://dx.doi.org/10.1175/2010mwr3478.1.
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Abstract The standard and polar versions 3.1.1 of the Weather Research and Forecasting (WRF) model, both initialized by the 40-yr ECMWF Re-Analysis (ERA-40), were run in Antarctica for July 1998. Four different boundary layer–surface layer–radiation scheme combinations were used in the standard WRF. The model results were validated against observations of the 2-m temperature, surface pressure, and 10-m wind speed at 9 coastal and 2 inland stations. The best choice for boundary layer and radiation parameterizations of the standard WRF turned out to be the Yonsei University boundary layer scheme in conjunction with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) surface layer scheme and the Rapid Radiative Transfer Model for longwave radiation. The respective temperature bias was on the order of 3°C less than the biases obtained with the other combinations. Increasing the minimum value for eddy diffusivity did, however, improve the performance of the asymmetric convective scheme by 0.8°C. Averaged over the 11 stations, the error growths in 24-h forecasts were almost identical for the standard and Polar WRF, but in 9-day forecasts Polar WRF gave a smaller 2-m temperature bias. For the Vostok station, however, the standard WRF gave a less positively biased 24-h temperature forecast. On average, the polar version gave the least biased surface pressure simulation. The wind speed simulation was characterized by low correlation values, especially under weak winds and for stations surrounded by complex topography.
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Yoshimura, Kei, and Masao Kanamitsu. "Dynamical Global Downscaling of Global Reanalysis." Monthly Weather Review 136, no. 8 (2008): 2983–98. http://dx.doi.org/10.1175/2008mwr2281.1.
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Abstract With the aim of producing higher-resolution global reanalysis datasets from coarse-resolution reanalysis, a global version of the dynamical downscaling using a global spectral model is developed. A variant of spectral nudging, the modified form of scale-selective bias correction developed for regional models is adopted. The method includes 1) nudging of temperature in addition to the zonal and meridional components of winds, 2) nudging to the perturbation field rather than to the perturbation tendency, and 3) no nudging and correction of the humidity. The downscaling experiment was performed using a T248L28 (about 50-km resolution) global model, driven by the so-called R-2 reanalysis (T62L28 resolution, or about 200-km resolution) during 2001. Evaluation with high-resolution observations showed that the monthly averaged global surface temperature and daily variation of precipitation were much improved. Over North America, surface wind speed and temperature are much better, and over Japan, the diurnal pattern of surface temperature is much improved, as are wind speed and precipitation, but not humidity. Three well-known synoptic/subsynoptic-scale weather patterns over the United States, Europe, and Antarctica were shown to become more realistic. This study suggests that the global downscaling is a viable and economical method for obtaining high-resolution reanalysis without rerunning a very expensive high-resolution full data assimilation.
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Hawes, T. C., M. R. Worland, P. Convey, and J. S. Bale. "Aerial dispersal of springtails on the Antarctic Peninsula: implications for local distribution and demography." Antarctic Science 19, no. 1 (2007): 3–10. http://dx.doi.org/10.1017/s0954102007000028.
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Aerial dispersal has been frequently proposed as a potential mechanism by which polar terrestrial arthropods are transported to, and settle the ice free habitats of Antarctica, but to date there has been little substantive evidence in support of this hypothesis. Using water traps we investigated aerial deposition of arthropods on Lagoon Island, Ryder Bay, on the Antarctic Peninsula. Over a period of five weeks, trapping at three different altitudes, we captured a total of nine springtails, Cryptopygus antarcticus, all alive. This is the first study to demonstrate conclusively the survival of wind-borne native arthropods within Antarctica. By scaling the modest trapping area and success against island surface area, it is clear that hundreds, if not thousands, of springtails are regularly relocated by winds between the terrestrial habitats of Marguerite Bay. We use known desiccation rates of C. antarcticus and wind speeds to predict the likelihood of successful dispersal between the principal terrestrial habitats of the larger Marguerite Bay. Implications for local and long-range dispersal are discussed in relation to C. antarcticus and other polar arthropods.
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Eisen, Olaf, Wolfgang Rack, Uwe Nixdorf, and Frank Wilhelms. "Characteristics of accumulation around the EPICA deep-drilling site in Dronning Maud Land, Antarctica." Annals of Glaciology 41 (2005): 41–46. http://dx.doi.org/10.3189/172756405781813276.
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AbstractBased on ground-penetrating radar profiles, we analyze area-wide spatial and temporal characteristics of accumulation rate in the vicinity of the EPICA (European Project for Ice Coring in Antarctica) deep-drilling site in Dronning Maud Land, Antarctica (EDML). An area of 1600km2 is covered by 500km of radar profiles, organized in a star-like pattern with eight 20–25km legs and a 10km grid with 1–3km spacing, each pattern being centred on the EDML drilling location. Distributions of density, cumulative mass, age and the electromagnetic wave speed with depth are available from physical ice-core records. Nine internal reflection horizons are continuously tracked within the upper 110m of ice over the whole area, yielding a spatial picture of accumulation rate history over >1000 years. The mean accumulation rate over the last 153 years varies between 50 and 75 kgm–2 a–1 over 50 km perpendicular to the ice divide; the spatial average is ~61 kgm–2 a–1. This general pattern is overlain by small-scale variations of accumulation rate on the order of 10% of the mean. Maximum local gradients in accumulation rate are ~2–3 kgm–2 a–1 km–1, about five times the regional accumulation rate gradient. Comparison of topography and accumulation rate along a 20 km profile in the direction of the mean winds indicates that variations in accumulation rate over short distances are linked to surface undulations. Our results show that advected spatial variations of accumulation rate are on the same order and even exceed temporal changes over the investigated periods. Ice flow and upstream effects therefore might influence accumulation rates reconstructed from the EDML ice core.
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Bello, Ana Belén, Francisco Navarro, Javier Raposo, Mónica Miranda, Arturo Zazo, and Marina Álvarez. "Fixed-Wing UAV Flight Operation under Harsh Weather Conditions: A Case Study in Livingston Island Glaciers, Antarctica." Drones 6, no. 12 (2022): 384. http://dx.doi.org/10.3390/drones6120384.
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How do the weather conditions typical of the polar maritime glaciers in the western Antarctic Peninsula region affect flight operations of fixed-wing drones and how should these be adapted for a successful flight? We tried to answer this research question through a case study for Johnsons and Hurd glaciers, Livingston Island, using a fixed-wing RPAS, in particular, a Trimble UX5 UAV with electric pusher propeller by brushless 700 W motor, chosen for its ability to fly long distances and reach inaccessible areas. We also evaluated the accuracy of the point clouds and digital surface models (DSM) generated by aerial photogrammetry in our case study. The results were validated against ground control points taken by differential GNSS techniques, showing an accuracy of 0.16 ± 0.12 m in the vertical coordinate. Various hypotheses were proposed and flight-tested, based on variables affecting the flight operation and the data collection, namely, gusty winds, low temperatures, battery life, camera configuration, and snow reflectivity. We aim to provide some practical guidelines that can help other researchers using fixed-wing drones under climatic conditions similar to those of the South Shetland Islands. Performance of the drone under harsh weather conditions, the logistical considerations, and the amount of snow at the time of data collection are factors driving the necessary modifications from those of conventional flight operations. We make suggestions concerning wind speed and temperature limitations, and avoidance of sudden fog banks, aimed to improve the planning of flight operations. Finally, we make some suggestions for further research.
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Jonsson, Stig, and Per Holmlund. "Evaporation Of Snow and Ice In Scharffenbergbotnen, Dronning Maud Land, Antarctica." Annals of Glaciology 14 (1990): 342. http://dx.doi.org/10.3189/s0260305500009071.
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Scharffenbergbotnen is a 3 × 6 km large basin of interior ice drainage on the north-western side of Heimefrontfjella in Dronning Maud Land, Antarctica. The elevation at the bottom of the depression is 1142 m a.s.l., while bedrock immediately to the south-east of this point rises to more than 2750 m. Ice enters the basin mainly from a low ice divide (1250 m a.s.l.) in the west but also through a 400 m high icefall in the east. Two separate blue-ice areas constitute approximately half the surface of the basin, while the other half is snow-covered.As part of SWEDARP (Swedish Antarctic Research Programme) 1988 a research project to study the origin and mass balance of this basin has been initiated. A net of 28 stakes has been established for studies of ablation and ice movement (Fig. 1). The ice thickness was measured by radio-echo sounding (Fig. 2) and particular care was devoted to get the correct ice depths at the entrance to the basin. The ice thickness along a central section of the basin varied from 1000 m in the west to 400 m at the bottom of the depression.In order to explain the ablation two automatic weather stations (Aanderaa 2700) were operated during the field season (mid-January to mid-February 1988). One was placed in the bottom of the depression, the other 13 km to the west in an area where a small net accumulation took place during the field season. The latter station should record “normal” weather. Sensors registering wind speed, wind gust, wind direction, incoming solar radiation, air temperature and relative humidity were installed at both weather stations, while reflected solar radiation, net radiation and air pressure were measured only at Scharffenbergbotnen. All sensors except the air pressure sensor were placed 270 cm above the ground, and all were read every 10 minutes.Ablation measurements were carried out between 16 January and 18 February on 24 of the stakes. 12 of these stakes were standing in snow. All but one recorded ablation and, as no signs of melting could be seen, all ablation must be due to evaporation and perhaps for the snowy areas some wind erosion. The average ablation rate for the whole field season was 0.7 mm w.eq. per day with a standard deviation of 0.3. Stakes in blue ice showed slightly higher values than those in snow. For January, when air temperatures always were above −10°C, the average ablation rate was 1.2 mm w.eq. per day.A regional difference in ablation rate across the depression was also measurable. Maximum ablation took place immediately below the arête forming the north-eastern boundary of the basin and diminished towards south-west. Below the arête the ablation rate was above 1 mm w.eq. per day for the whole field season and more than 2 mm w.eq. per day during January.A comparison of weather data between the two stations showed the following main differences. In the depression the temperature showed no daily variation and relative humidity varied between 40 and 60%. The weather at the other station was characterised by colder nights and weaker winds as well as by a relative humidity between 60 and 80%. The reason for the regional variation in ablation can be explained by almost constant easterly winds during January and the drop in altitude (between 300 and 500 m) along the north-western arête.On 11 February 1988 the weather station at Scharffenbergbotnen was converted into a system for satellite (Argos) transmission of weather data to Europe. The transmission seems to have been successful but the data are not yet processed. At present (January 1989) one of us is remeasuring the stakes (ablation and ice movement) during SWEDARP 1989. Preliminary results sent by radio point towards a yearly net ablation rate of 120 mm w.eq. for the blue-ice area in the bottom of the depression. 25% of the ablation took place during the field season 1988, but 75% has evaporated between 18 February 1988 and mid-January 1989. Probably most of the evaporation took place during December 1988 and January 1989, which means a very high daily evaporation rate (2.5 mm w.eq. per day).