Academic literature on the topic 'Wind forecasting Antarctica'

Abstract The interaction of synoptic and mesoscale circulations with the steep topography surrounding the Ross Ice Shelf, Antarctica, greatly influences the wind patterns in the region of the Ross Ice Shelf. The topography provides forcing for features such as katabatic winds, barrier winds, and barrier wind corner jets. The combination of topographic forcing and synoptic and mesoscale forcing from cyclones that traverse the Ross Ice Shelf sector create a region of strong but varying winds. This paper identifies the dominant surface wind patterns over the Ross Ice Shelf using output from the Weather Research and Forecasting Model run within the Antarctic Mesoscale Prediction System and the method of self-organizing maps (SOM). The dataset has 15-km grid spacing and is the first study to identify the dominant surface wind patterns using data at this resolution. The analysis shows that the Ross Ice Shelf airstream, a dominant stream of air flowing northward from the interior of the continent over the western and/or central Ross Ice Shelf to the Ross Sea, is present over the Ross Ice Shelf approximately 34% of the time, the Ross Ice Shelf airstream varies in both its strength and position over the Ross Ice Shelf, and barrier wind corner jets are present in the region to the northwest of the Prince Olav Mountains approximately 14% of the time and approximately 41% of the time when the Ross Ice Shelf airstream is present.

Abstract This study initiates the application of the maturing Weather Research and Forecasting (WRF) model to the polar regions in the context of the real-time Antarctic Mesoscale Prediction System (AMPS). The behavior of the Advanced Research WRF (ARW) in a high-latitude setting and its ability to capture a significant Antarctic weather event are investigated. Also, in a suite of sensitivity tests, the impacts of the assimilation of Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric motion vectors on ARW Antarctic forecasts are explored. The simulation results are analyzed and the statistical significance of error differences is assessed. It is found that with the proper consideration of MODIS data the ARW can accurately simulate a major Antarctic event, the May 2004 McMurdo windstorm. The ARW simulations illuminate an episode of high-momentum flow responding to the complex orography of the vital Ross Island region. While the model captures the synoptic setting and basic trajectory of the cyclone driving the event, there are differences on the mesoscale in the evolution of the low pressure system that significantly affect the forecast results. In general, both the ARW and AMPS’s fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) tend to underforecast the wind magnitudes, reflecting their stalling and filling of the system near Ross Island. It is seen, however, that both targeted data assimilation and grid resolution enhancement can yield improvement in the forecast of the key parameter of wind speed. It is found that the assimilation of MODIS observations can significantly improve the forecast for a high-impact Antarctic weather event. However, the application to the retrievals of a filter accounting for instrument channel, observation height, and surface type is necessary. The results indicate benefits to initial conditions and high-resolution, polar, mesoscale forecasts from the careful assimilation of nontraditional satellite observations over Antarctica and the Southern Ocean.

AbstractThe topographical effect on a strong wind event that occurred on 7 January 2013 at King Sejong Station (KSJ), Antarctica, was investigated using the Polar Weather Research and Forecasting (WRF) model. Numerical experiments applying three different terrain heights of the Antarctic Peninsula (AP) were performed to quantitatively estimate the topographical effect on the selected strong wind event. The experiment employing original AP topography successfully represented the observed features in the strong wind event, both in terms of peak wind speed (by ~94%; ~19.7 m/s) and abrupt transitions of wind speed. In contrast, the experiment with a flattened terrain height significantly underestimated the peak wind speeds (by ~51%; ~10.4 m/s) of the observations. An absence of AP topography failed to simulate both a strong discontinuity of sea-level pressure fields around the east coast of the AP and a strong south-easterly wind over the AP. As a result, the observed downslope windstorm, driven by a flow overriding a barrier, was not formed at the western side of the AP, resulting in no further enhancement of the wind at KSJ. This result demonstrates that the topography of the AP played a critical role in driving the strong wind event at KSJ on 7 January 2013, accounting for ~50% of the total wind speed.

Abstract Casey Station in East Antarctica is not often subject to strong southerly flow off the Antarctic continent but when such events occur, operations at the station are often adversely impacted. Not only are the dynamics of such events poorly understood, but the forecasting of such occurrences is difficult. The following study uses model output from a 12-month experiment using the Antarctic Limited-Area Prediction System (ALAPS) to advance the understanding of the dynamics of such events and postulates that what are often described as katabatic wind events are more likely to be synoptic in scale, with mid- and upper-level tropospheric dynamics forcing the surface layer flow. Strong surface layer flows that have a katabatic signature commonly develop on the steep Antarctic escarpment but rarely extend out over the coast in the Casey area, most probably as a result of cold air damming. However, the development of a strong south-southwesterly jet over Casey provides a mechanism whereby the katabatic can move out off the coast.

AbstractAn experiment applying controlled meteorological (CMET) balloons near the coast of Dronning Maud Land, Antarctica, in January 2013 is described. Two balloons were airborne for 60 and 106 hours with trajectory lengths of 885.8 km and 2367.4 km, respectively. The balloons carried out multiple controlled soundings on the atmospheric pressure, temperature and humidity up to 3.3 km. Wind speed and direction were derived from the balloon drift. Observations were compared with radiosonde sounding profiles from the Halley Research Station, and applied in evaluating simulations carried out with the weather research and forecasting (WRF) mesoscale atmospheric model. The most interesting feature detected by the CMET balloons was a mesoscale anticyclone over the Weddell Sea and the coastal zone, which was reproduced by the WRF model with reduced intensity. The modelled wind speed was up to 10 m s-1 slower and the relative humidity was 20–40% higher than the observed values. However, over the study period the WRF results generally agreed with the observations. The results suggest that CMET balloons could be an interesting supplement to Antarctic atmospheric observations, particularly in the free troposphere.

The tangent linear and adjoint of an adiabatic version of the Weather Research and Forecasting (WRF) Model with its Advanced Research WRF (ARW) dynamic core have been developed. The source-to-source automatic differentiation tool [i.e., the Transformation of Algorithm (TAF) in FORTRAN] was used in the development. Tangent linear and adjoint checks of the developed adiabatic WRF adjoint modeling system (WAMS) were conducted, and all necessary correctness verification procedures were passed. As the first application, the adiabatic WAMS was used to study the adjoint sensitivity of a severe windstorm in Antarctica. Linearity tests indicated that an adjoint-based sensitivity study with the Antarctic Mesoscale Prediction System (AMPS) 90-km domain configuration for the windstorm is valid up to 24 h. The adjoint-based sensitivity calculation with adiabatic WAMS identified sensitive regions for the improvement of the 24-h forecast of the windstorm. It is indicated that the windstorm forecast largely relies on the model initial conditions in the area from the south part of the Trans-Antarctic Mountains to West Antarctica and between the Ross Ice Shelf and the South Pole. Based on the sensitivity analysis, the southerly or southeasterly wind at lower levels in the sensitivity region should be larger, the cyclone should be stronger, and the atmospheric stratification should be more stable over the north slope of the Trans-Antarctic Mountain to the Ross Ice Shelf, than the AMPS analyses. By constructing pseudo-observations in the sensitivity region using the gradient information of forecast windstorm intensity around McMurdo, the model initial conditions are revised with the WRF three-dimensional variational data assimilation, which leads to significant improvement in the prediction of the windstorm. An adjoint sensitivity study is an efficient way to identify sensitivity regions in order to collect more observations in the region for better forecasts in a specific aspect of interest.

India along with South America, Africa, Antarctica, and Australia was part of the supercontinent Gondwana some 140 million years ago. When the supercontinent split up, the Indian plat moved north-eastward while the Australian and African plates moved comparatively less distance and at much lower speeds. The Antarctica remained almost stationary. The 37th Indian Scientific Expedition to Antarctica was the fourth wintering of India Meteorological Department (IMD) members at Bharati station, Larsemann Hills, Antarctica. During the expedition recording of meteorological surface & upper air observations, vertical ozone measurement, continuous weather monitoring and forecasting were performed. All these meteorological parameters were thoroughly analyzed and studied. Temperature analysis showed that the coldest month was September and warmest was January. Strong and persistent north-easterly near-surface winds were observed throughout the year with May being the windiest month. During the period, 9 numbers of blizzards spanning a period of 15 days were observed with a maximum wind gust of 80 knots during a blizzard on 5th August 2018. During the expedition, a total of 32 balloon-borne GPS based ozone sonde ascents were taken and their analysis showed that the minimum thickness of ozone concentration is found between 15th September and 10th October. Also, the space weather, special meteorological phenomena and fauna found near Bharati station was observed and documented in this study.

Abstract. Winds measured by lidar from the Aeolus satellite are compared with winds measured by two ground-based radars – MARA in Antarctica (70.77∘ S, 11.73∘ E) and ESRAD (67.88∘ N, 21.10∘ E) in Arctic Sweden – for the period 1 July–31 December 2019. Aeolus is a demonstrator mission to test whether winds measured by Doppler lidar from space can have sufficient accuracy to contribute to improved weather forecasting. A comprehensive programme of calibration and validation has been undertaken following the satellite launch in 2018, but, so far, direct comparison with independent measurements from the Arctic or Antarctic regions have not been made. The comparison covers heights from the low troposphere to just above the tropopause. Results for each radar site are presented separately for Rayleigh (clear) winds, Mie (cloudy) winds, sunlit (“summer”) and non-sunlit (“winter”) seasons, and ascending and descending satellite tracks. Horizontally projected line-of-sight (HLOS) winds from Aeolus, reprocessed using baseline 2B10, for passes within 100 km of the radar sites, are compared with HLOS winds calculated from 1 h averaged radar horizontal wind components. The agreement in most data subsets is very good, with no evidence of significant biases (<1 m s−1). Possible biases are identified for two subsets (about −2 m s−1 for the Rayleigh winds for the descending passes at MARA and about 2 m s−1 for the Mie winds for the ascending passes at ESRAD, both in winter), but these are only marginally significant. A robust significant bias of about 7 m s−1 is found for the Mie winds for the ascending tracks at MARA in summer. There is also some evidence for increased random error (by about 1 m s−1) for the Aeolus Mie winds at MARA in summer compared to winter. This might be related to the presence of sunlight scatter over the whole of Antarctica as Aeolus transits across it during summer.

Abstract. Tropopause folds are one of the mechanisms of stratosphere–troposphere exchange, which can bring ozone rich stratospheric air to low altitudes in the extra-tropical regions. They have been widely studied at northern mid- or high latitudes, but so far almost no studies have been made at mid- or high southern latitudes. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has operated at the Swedish summer station Wasa, Antarctica (73° S, 13.5° W) during austral summer seasons from 2007 to 2011 and has observed on several occasions signatures similar to those caused by tropopause folds at comparable Arctic latitudes. Here a case study is presented of one of these events when an ozonesonde successfully sampled the fold. Analysis from European Center for Medium Range Weather Forecasting (ECMWF) is used to study the circumstances surrounding the event, and as boundary conditions for a mesoscale simulation using the Weather Research and Forecasting (WRF) model. The fold is well resolved by the WRF simulation, and occurs on the poleward side of the polar jet stream. However, MARA resolves fine-scale layering associated with the fold better than the WRF simulation.

Abstract Accurate representation of the stability of the surface layer in numerical weather prediction models is important because of the impact it has on forecasts of surface energy, moisture, and momentum fluxes. It also impacts boundary layer processes such as the generation of turbulence, the creation of near-surface flows, and fog formation. This paper uses observations from a 30-m automatic weather station on the Ross Ice Shelf, Antarctica, to evaluate the near-surface layer in the Antarctic Mesoscale Prediction System (AMPS), a numerical weather prediction system used for forecasting in Antarctica. The method of self-organizing maps (SOM) is used to identify characteristic potential temperature anomaly profiles observed at the 30-m tower. The SOM-identified profiles are then used to evaluate the performance of AMPS as a function of atmospheric stability. The results indicate AMPS underpredicts the frequency of near-neutral profiles and instead overpredicts the frequency of weakly unstable and weak to moderately stable profiles. AMPS does not forecast the strongest statically stable patterns observed by Tall Tower, but in the median, the AMPS forecasts are more statically stable across all wind speeds, indicating a possible mechanical mixing error or a negative radiation bias. The SOM analysis identifies a negative radiation bias under near-neutral to weakly stable conditions, causing an overrepresentation of the static stability in AMPS. AMPS has a positive wind speed bias in moderate to strongly stable conditions, which generates too much mechanical mixing and an underrepresentation of the static stability. Model errors increase with increasing atmospheric stability.

Antarctic Wind Engineering deals with the effects of wind on the built environment. The assessment of wind induced forces, wind resource and wind driven snowdrifts are the main tasks for a wind engineer when participating on the design of an Antarctic building. While conventional Wind Engineering techniques are generally applicable to the Antarctic environment, there are some aspects that require further analysis due to the special characteristics of the Antarctic wind climate and its boundary layer meteorology.

The first issue in remote places like Antarctica is the lack of site wind measurements and meteorological information in general. In order to complement this shortage of information various meteorological databases have been surveyed. Global Reanalyses, produced by the European Met Office ECMWF, and RACMO/ANT mesoscale model simulations, produced by the Institute for Marine and Atmospheric Research of Utrecht University (IMAU), have been validated versus independent observations from a network of 115 automatic weather stations. The resolution of these models, of some tens of kilometers, is sufficient to characterize the wind climate in areas of smooth topography like the interior plateaus or the coastal ice shelves. In contrast, in escarpment and coastal areas, where the terrain gets rugged and katabatic winds are further intensified in confluence zones, the models lack resolution and underestimate the wind velocity.

The Antarctic atmospheric boundary layer (ABL) is characterized by the presence of strong katabatic winds that are generated by the presence of surface temperature inversions in sloping terrain. This inversion is persistent in Antarctica due to an almost continuous cooling by longwave radiation, especially during the winter night. As a result, the ABL is stably stratified most of the time and, only when the wind speed is high it becomes near neutrally stratified. This thesis also aims at making a critical review of the hypothesis underlying wind engineering models when extreme boundary layer situations are faced. It will be shown that the classical approach of assuming a neutral log-law in the surface layer can hold for studies of wind loading under strong winds but can be of limited use when detailed assessments are pursued.

The Antarctic landscape, mostly composed of very long fetches of ice covered terrain, makes it an optimum natural laboratory for the development of homogeneous boundary layers, which are a basic need for the formulation of ABL theories. Flux-profile measurements, made at Halley Research Station in the Brunt Ice Shelf by the British Antarctic Survery (BAS), have been used to analyze boundary layer similarity in view of formulating a one-dimensional ABL model. A 1D model of the neutral and stable boundary layer with a transport model for blowing snow has been implemented and verified versus test cases of the literature. A validation of quasi-stationary homogeneous profiles at different levels of stability confirms that such 1D models can be used to classify wind profiles to be used as boundary conditions for detailed 3D computational wind engineering studies.

A summary of the wind engineering activities carried out during the design of the Antarctic Research Station is provided as contextual reference and point of departure of this thesis. An elevated building on top of sloping terrain and connected to an under-snow garage constitutes a challenging environment for building design. Building aerodynamics and snowdrift management were tested in the von Karman Institute L1B wind tunnel for different building geometries and ridge integrations. Not only for safety and cost reduction but also for the integration of renewable energies, important benefits in the design of a building can be achieved if wind engineering is considered since the conceptual phase of the integrated building design process.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

Thesis (M.S.)--University of Wisconsin--Madison, 1994.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 111-113).