scholarly journals Reexamination of the Near-Surface Airflow over the Antarctic Continent and Implications on Atmospheric Circulations at High Southern Latitudes*

2007 ◽  
Vol 135 (5) ◽  
pp. 1961-1973 ◽  
Author(s):  
Thomas R. Parish ◽  
David H. Bromwich
Keyword(s):  
Mesoscale Model ◽  
Numerical Models ◽  
Weather Prediction ◽  
Ice Sheets ◽  
Lower Atmosphere ◽  
Diagnostic Model ◽  
Near Surface ◽  
Antarctic Continent ◽  
The Mean ◽  
The Antarctic

Abstract Previous work has shown that winds in the lower atmosphere over the Antarctic continent are among the most persistent on earth with directions coupled to the underlying ice topography. In 1987, Parish and Bromwich used a diagnostic model to depict details of the Antarctic near-surface airflow. A radially outward drainage pattern off the highest elevations of the ice sheets was displayed with wind speeds that generally increase from the high interior to the coast. These winds are often referred to as “katabatic,” with the implication that they are driven by radiational cooling of near-surface air over the sloping ice terrain. It has been shown that the Antarctic orography constrains the low-level wind regime through other forcing mechanisms as well. Dynamics of the lower atmosphere have been investigated increasingly by the use of numerical models since the observational network over the Antarctic remains quite sparse. Real-time numerical weather prediction for the U.S. Antarctic Program has been ongoing since the 2000–01 austral summer season via the Antarctic Mesoscale Prediction System (AMPS). AMPS output, which is based on a polar optimized version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model, is used for a 1-yr period from June 2003 to May 2004 to investigate the mean annual and seasonal airflow patterns over the Antarctic continent to compare with previous streamline depictions. Divergent outflow from atop the continental interior implies that subsidence must exist over the continent and a direct thermal circulation over the high southern latitudes results. Estimates of the north–south mass fluxes are obtained from the mean airflow patterns to infer the influence of the elevated ice sheets on the mean meridional circulation over Antarctica.

scholarly journals The Climate of the McMurdo, Antarctica, Region as Represented by One Year of Forecasts from the Antarctic Mesoscale Prediction System*

2005 ◽  
Vol 18 (8) ◽  
pp. 1174-1189 ◽  
Author(s):  
Andrew J. Monaghan ◽  
David H. Bromwich ◽  
Jordan G. Powers ◽  
Kevin W. Manning
Keyword(s):  
Ross Sea ◽  
Mesoscale Model ◽  
Weather Prediction ◽  
Cloud Fraction ◽  
Important Influence ◽  
Limited Area ◽  
Dry Valleys ◽  
Prediction System ◽  
Near Surface ◽  
The Antarctic

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.

Real-Time Forecasting for the Antarctic: An Evaluation of the Antarctic Mesoscale Prediction System (AMPS)*

2005 ◽  
Vol 133 (3) ◽  
pp. 579-603 ◽  
Author(s):  
David H. Bromwich ◽  
Andrew J. Monaghan ◽  
Kevin W. Manning ◽  
Jordan G. Powers
Keyword(s):  
Surface Pressure ◽  
Mesoscale Model ◽  
Weather Prediction ◽  
Surface Wind ◽  
Windward Side ◽  
Prediction System ◽  
Free Atmosphere ◽  
Near Surface ◽  
The Antarctic ◽  
The Impact

Abstract In response to the need for improved weather prediction capabilities in support of the U.S. Antarctic Program’s field operations, the Antarctic Mesoscale Prediction System (AMPS) was implemented in October 2000. AMPS employs the Polar MM5, a version of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model optimized for use over ice sheets. The modeling system consists of several domains ranging in horizontal resolution from 90 km covering a large part of the Southern Hemisphere to 3.3 km over the complex terrain surrounding McMurdo, the hub of U.S. operations. The performance of the 30-km AMPS domain versus observations from manned and automatic weather stations is statistically evaluated for a 2-yr period from September 2001 through August 2003. The simulated 12–36-h surface pressure and near-surface temperature at most sites have correlations of r > 0.95 and r > 0.75, respectively, and small biases. Surface wind speeds reflect the complex topography and generally have correlations between 0.5 and 0.6, and positive biases of 1–2 m s−1. In the free atmosphere, r > 0.95 (geopotential height), r > 0.9 (temperature), and r > 0.8 (wind speed) at most sites. Over the annual cycle, there is little interseasonal variation in skill. Over the length of the forecast, a gradual decrease in skill is observed from hours 0–72. One exception is the surface pressure, which improves slightly in the first few hours, due in part to the model adjusting from surface pressure biases that are caused by the initialization technique over the high, cold terrain. The impact of the higher-resolution model domains over the McMurdo region is also evaluated. It is shown that the 3.3-km domain is more sensitive to spatial and temporal changes in the winds than the 10-km domain, which represents an overall improvement in forecast skill, especially on the windward side of the island where the Williams Field and Pegasus runways are situated, and in the lee of Ross Island, an important area of mesoscale cyclogenesis (although the correlation coefficients in these regions are still relatively low).

Intercomparison of Mesoscale Model Simulations of the Daytime Valley Wind System

2011 ◽  
Vol 139 (5) ◽  
pp. 1389-1409 ◽  
Author(s):  
Juerg Schmidli ◽  
Brian Billings ◽  
Fotini K. Chow ◽  
Stephan F. J. de Wekker ◽  
James Doyle ◽  
...  
Keyword(s):  
Land Surface ◽  
Mesoscale Model ◽  
Numerical Models ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Surface Wind Speed ◽  
Time Shift ◽  
Wind System ◽  
Valley Wind ◽  
The Mean

Three-dimensional simulations of the daytime thermally induced valley wind system for an idealized valley–plain configuration, obtained from nine nonhydrostatic mesoscale models, are compared with special emphasis on the evolution of the along-valley wind. The models use the same initial and lateral boundary conditions, and standard parameterizations for turbulence, radiation, and land surface processes. The evolution of the mean along-valley wind (averaged over the valley cross section) is similar for all models, except for a time shift between individual models of up to 2 h and slight differences in the speed of the evolution. The analysis suggests that these differences are primarily due to differences in the simulated surface energy balance such as the dependence of the sensible heat flux on surface wind speed. Additional sensitivity experiments indicate that the evolution of the mean along-valley flow is largely independent of the choice of the dynamical core and of the turbulence parameterization scheme. The latter does, however, have a significant influence on the vertical structure of the boundary layer and of the along-valley wind. Thus, this ideal case may be useful for testing and evaluation of mesoscale numerical models with respect to land surface–atmosphere interactions and turbulence parameterizations.

scholarly journals Snow density along the route traversed by the Japanese-Swedish Antarctic Expedition 2007/08

2012 ◽  
Vol 58 (209) ◽  
pp. 529-539 ◽  
Author(s):  
Shin Sugiyama ◽  
Hiroyuki Enomoto ◽  
Shuji Fujita ◽  
Kotaro Fukui ◽  
Fumio Nakazawa ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Coastal Region ◽  
Snow Density ◽  
Syowa Station ◽  
Near Surface ◽  
A Value ◽  
Surface Snow ◽  
The Mean ◽  
The Antarctic

AbstractDuring the Japanese-Swedish Antarctic traverse expedition of 2007/08, we measured the surface snow density at 46 locations along the 2800 km long route from Syowa station to Wasa station in East Antarctica. The mean snow density for the upper 1 (or 0.5) m layer varied from 333 to 439 kg m-3 over a region spanning an elevation range of 365-3800 ma.s.l. The density variations were associated with the elevation of the sampling sites; the density decreased as the elevation increased, moving from the coastal region inland. However, the density was relatively insensitive to the change in elevation along the ridge on the Antarctic plateau between Dome F and Kohnen stations. Because surface wind is weak in this region, irrespective of elevation, the wind speed was suggested to play a key role in the near-surface densification. The results of multiple regression performed on the density using meteorological variables were significantly improved by the inclusion of wind speed as a predictor. The regression analysis yielded a linear dependence between the density and the wind speed, with a coefficient of 13.5 kg m-3 (m s-1)-1. This relationship is nearly three times stronger than a value previously computed from a dataset available in Antarctica. Our data indicate that the wind speed is more important to estimates of the surface snow density in Antarctica than has been previously assumed.

Planetary aerosol electrification: Lessons learned from a terrestrial analogy for Venus

2021 ◽  
Author(s):  
Amethyst Johnson ◽  
Karen Aplin
Keyword(s):  
Atmospheric Stability ◽  
Ionic Mobility ◽  
Mean Free Path ◽  
Lessons Learned ◽  
Lower Atmosphere ◽  
Aerosol Layer ◽  
Electrical Measurements ◽  
Near Surface ◽  
Charged Aerosol ◽  
The Mean

<p>Planetary atmospheric electrification has the potential to damage spacecraft, yet for planets with thick, deep atmospheres such as Venus, the level of electrification remains open to interpretation. Partly due to the difficulty of access and potential hostility to spacecraft, there are limited in-situ observations of deep atmospheres, making terrestrial analogies attractive. One proposed explanation of the observations of near-surface electrification on Venus from sensors on Venera 13 & 14 is a haze of charged aerosol. As the Sahara is an environment with lofted dust that is potentially similar to Venus in terms of atmospheric stability, a simple model was developed estimating a mean aerosol charge based on typical Saharan haze aerosol distributions. Spacecraft surface area and descent speeds were used to estimate the accumulated charge and discharge current measured by the Venera missions, but this model underestimated Venera's electrical measurements by three orders of magnitude. This suggests that an aerosol layer alone cannot explain the charge apparently present in the lower atmosphere of Venus. The simple terrestrial analogy employed may not have been suitable due to the modified pressure and temperature profile affecting the mean free path, ionic mobility and consequently the mean charge. Discrepancies in atmospheric stability and wind patterns must also be evaluated, as the effect of terrestrial wind on aerosol distributions may not be directly applicable to other planets. More detailed calculations of ion-aerosol attachment and re-evaluation of the terrestrial analogy may be able to resolve some these issues, but it looks likely that additional significant sources of charge are required to explain the Venera observations. Triboelectric charging of lofted surface material could exceed charging observed in terrestrial situations, or some unknown atmospheric or non-atmospheric source of charge could have contributed to the Venera electrical measurements. </p>

scholarly journals Accumulation in Antarctica and Greenland derived from passive-microwave data: a comparison with contoured compilations

1995 ◽  
Vol 21 ◽  
pp. 123-130 ◽  
Author(s):  
H. Jay Zwally ◽  
MARIO B. Giovinetto
Keyword(s):  
Field Data ◽  
Grid Point ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Hyperbolic Function ◽  
West Antarctica ◽  
The Mean ◽  
The Antarctic ◽  
Mass Accumulation

The annual rate of net mass accumulation at the surface in the Antarctic and Greenland ice sheets is determined from firn emissivity based on Nimbus-5 ESMR and Nimbus-7 THIR data. In this study the determinations are limited to the areas of dry-snow facies and are based on a hyperbolic function of emissivity. Two coefficients of the function are selected for particular regions of each ice sheet after a comparison with field data selected for their reliability (82 stations in East Antarctica, 69 stations in West Antarctica and 89 stations in Greenland). Derived accumulation values are produced for grid-point locations 100 km apart which cover 56–94% of the dry-snow areas and 32–58% of the accumulation areas of each ice sheet. These values are compared with interpolated values obtained from the latest contoured compilations of field data. The means of derived values for East and West Antarctica are 12% and 39% larger, respectively, than the mean obtained from interpolated values, suggesting that the isopleth patterns as drawn in the compilation of field data lead to underestimates. The mean of derived values for Greenland is 5% smaller than the mean obtained from interpolated values, suggesting that the compilation of field data may lead to small overestimates that are within the error of determination and the variability of accumulation. Improving facies zonation and the determination of coefficients for the areas of upper percolation facies should improve these preliminary assessments.

scholarly journals A Practical Approach to Sequential Estimation of Systematic Error on Near-Surface Mesoscale Grids

2007 ◽  
Vol 22 (6) ◽  
pp. 1257-1273 ◽  
Author(s):  
Joshua P. Hacker ◽  
Daran L. Rife
Keyword(s):  
Statistical Analysis ◽  
Systematic Error ◽  
Mesoscale Model ◽  
Weather Prediction ◽  
Time Of Day ◽  
Isotropic Case ◽  
Observation Error ◽  
Localization Operators ◽  
Near Surface ◽  
Covariance Functions

Abstract Statistical analysis arguments are used to construct an estimation algorithm for systematic error of near-surface temperatures on a mesoscale grid. The systematic error is defined as the observed running-mean error, and an averaging length of 7 days is shown to be acceptable. Those errors are spread over a numerical weather prediction model grid via the statistical analysis equation. Two covariance models are examined: 1) a stationary, isotropic function tuned with the observed running-mean errors and 2) dynamic estimates derived from a recent history of running-mean forecasts. Prediction of error is possible with a diurnal persistence model, where the error at one time of day can be estimated from data with lags of 24-h multiples. The approach is tested on 6 months of 6-h forecasts with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) over New Mexico. Results show that for a quantity such as 2-m temperature, the systematic component of error can be effectively predicted on the grid. The gridded estimates fit the observed running-mean errors well. Cross validation shows that predictions of systematic error result in a substantial error reduction where observations are not available. The error estimates show a diurnal evolution, and are not strictly functions of terrain elevation. Observation error covariances, localization operators, and covariance functions in the isotropic case must be tuned for a specific forecast system and observing network, but the process is straightforward. Taken together, the results suggest an effective method for systematic error estimation on near-surface mesoscale grids in the absence of a useful ensemble. Correction for those errors may provide benefits to forecast users.

scholarly journals Drifting snow statistics from multiple-year autonomous measurements in Adelie Land, eastern Antarctica

2019 ◽  
Author(s):  
Charles Amory
Keyword(s):  
Temporal Frequency ◽  
Field Measurements ◽  
Near Surface ◽  
Continental Scale ◽  
Drifting Snow ◽  
Single Location ◽  
Antarctic Continent ◽  
Short Time ◽  
The Antarctic ◽  
Snow Transport

Abstract. Drifting snow is a widespread feature over the Antarctic ice sheet whose climatological and hydrological significances at the continental scale have been consequently investigated through modelling and satellite approaches. While field measurements are needed to evaluate and interpret model and punctual satellite products, most drifting snow observation campaigns in Antarctica involved data collected at a single location and over short time periods. With the aim of acquiring new data relevant to the observations and modelling of drifting snow in Antarctic conditions, two remote locations in coastal Adelie Land (East Antarctica) 100 km apart were instrumented in January 2010 with meteorological and second-generation IAV Engineering acoustic FlowCaptTM sensors. The data provided nearly continuously so far constitutes the longest dataset of autonomous near-surface (i.e., below 2 m) measurements of drifting snow currently available over the Antarctic continent. This paper presents an assessment of drifting snow occurrences and snow mass transport from up to 9 years (2010–2018) of half-hourly observational records collected in one of the Antarctic regions most prone to snow transport by wind. The dataset is freely available to the scientific community and can be used to complement satellite products and evaluate snow-transport models close to the surface and at high temporal frequency.

Aspects of modern Antarctic meteorology and climatology

2005 ◽  
Vol 32 (2) ◽  
pp. 334-345
Author(s):  
John Turner
Keyword(s):  
Southern Ocean ◽  
Southern Oscillation ◽  
Coastal Region ◽  
First Century ◽  
Near Surface ◽  
Weather Forecasts ◽  
Air Temperatures ◽  
Oceanic Climate ◽  
Antarctic Continent ◽  
The Antarctic

Great advances have been made in recent years in our understanding of the weather of the Antarctic and how the climate of the continent varies on a range of time-scales. The observations from the stations are still the most accurate meteorological measurements that we have, but satellites have been important in providing data for remote parts of the continent and the Southern Ocean. With the large amount of data that is available today weather forecasts are much more accurate than just a few years ago and can provide valuable guidance up to several days ahead over the Southern Ocean and Antarctic coastal region. However, predicting the weather for the interior of the Antarctic is still very difficult. Recent research has shown that the climate of the Antarctic is affected by tropical atmospheric and oceanic climate cycles, such as the El Niño-Southern Oscillation, but the links are complex. The picture of climate change across the Antarctic during the last 50 years is complex, with only the Antarctic Peninsula showing a significant warming. By the end of the twenty-first century near-surface air temperatures across much of the Antarctic continent are expected to increase by several degrees. A small increase in precipitation is also expected.

MAPPING THE ANTARCTIC ICE SHEET BY SATELLITE ALTIMETRY

1966 ◽  
Vol 3 (6) ◽  
pp. 893-901 ◽  
Author(s):  
G. de Q. Robin
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Ice Sheets ◽  
Systematic Errors ◽  
Contour Map ◽  
Antarctic Ice Sheet ◽  
Antarctic Continent ◽  
The Difference ◽  
Peripheral Areas ◽  
The Antarctic

It is proposed that a radio altimeter be installed in a satellite to measure its height above the surface. It should work at a frequency of the order of 104 Mc/s and measure heights to an accuracy as close as practicable to ± 5 m. Heights above the ocean would be extrapolated to calculate satellite heights above sea level while over the Antarctic continent, and the difference between this calculated height and the measured height would give the surface elevation. Geometrical sounding errors and systematic errors may cause errors up to 50 m on relatively flat ice sheets, but incremental errors over 10 km should be of the order of 10 m. The systematic coverage of the Antarctic continent by a few weeks' observations from a satellite should make a detailed contour map practicable. The system would not be satisfactory for the peripheral areas where many slopes exceed 1:200 and are less regular than elsewhere, but these areas are being surveyed by conventional methods.

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