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— Plot of all station barometric pressure data versus temperature, during day (top) and night (bottom); day refers to the sun at or above the horizon, and night to below. Solid red curves are the average sping and summer (day) and winter and fall (night) temperature profiles at Eureka; dashed curves are the averages of day and night; dotted curves, quartiles.
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Ellesmere Island, at the most northerly tip of Canada, possesses the highest mountain peaks within 10 degrees of the pole. The highest is 2616 m, with many summits over 1000 m, high enough to place them above a stable low-elevation thermal inversion that persists through winter darkness. Our group has studied four mountains along the northwestern c...
Contexts in source publication
Context 1
... 6.— Same as Figure 5, except for surface wind speed. Dashed black lines connect the median pressures and wind speeds for Eureka, PEARL, Site 11A, and 14A; solid lines are means; dotted lines are those plus one standard deviation.
...
Context 2
... second and third from top panels of Figure 4 are air temperature and pressure, respectively, for all stations. Dashed lines indicate the average measured pressues; the top dotted black line is mean air pressure at 2616 m for a standard atmospheric model (at 0 Celsius). Here day refers to all samples taken while the sun was above the horizon, and night while below. The strong near-sinusoidal variation of temperature and pressure with sun elevation is evident, and the onset of fall and winter conditions is strongly correlated with sun elevation falling below the horizon. A useful division between seasons then is to refer to all samples taken when the sun is above the horizon as “day” and all while below the horizon “night.” In climatology studies this would also be close to a clean division between fall-winter (sun down) and spring-summer (sun up). As the sun goes down, the winter low-altitude atmospheric thermal inversion quickly develops over much of the High Arctic. It is a remarkably stable phenomenon, intact throughout winter darkness. For Eureka, based on 50 years of balloon soundings, the base of the inversion is almost always at the surface from September through March, with a monthly median depth of about 800 m (Kahl, Serreze & Schnell 1992). At the peak of the inversion profile the temperature is typically 8 to 14 degrees warmer than the surface, which effectively excludes air below the inversion from rising and mixing with the free air above. Interestingly, the lower quartile height during the winter at Eureka is always below 600 m, that is, between 25% and 50% of the time it lies below the elevation of PEARL. The upper monthly quartile in winter for Eureka is below 1200 m. The situation is almost identical at Alert, with inversion depths shifted perhaps 100 m lower. Similar results are obtained for comparable Russian locations (Serreze, Kahl & Schnell 1992), and MODIS satellite results (Liu & Key 2003). The sharp contrast in air temperature profile relative to day and night is evident in Figure 5, where all station temperature data are plotted relative to barometric pressure. Because barometer data are missing for Ward Hunt Island, the mean temperature for day and night are given at the mean barometric pressure for the same time periods at Alert, which is the nearest with overlapping temporal coverage. Average sping/summer and winter/fall temperature profiles are shown for twice-daily Eureka aerosondes (Lesins, Duck & Drummond 2009). Assuming a consistent temperature profile along the coast, the data are consistent with Site 11A being above the inversion 75% of the time or more at night, and Site 14A always being above the inversion ...
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Citations
... A potential field campaign would ideally include, apart from standard meteorological sensors, instruments to measure cloud cover, turbulence and seeing. The experiences described in Steinbring et al (2010) in the Canadian Arctic provide an interesting example as to how such a field campaign could be carried out. Given that there exist doubts as to the viability of the sites, the most prudent course of action may be to collaborate with other groups also interested in obtaining meteorological observations in the area (glaciologists, geodesists and climatologists being obvious candidates). ...
The quality of ground based astronomical observations are significantly affected by telluric conditions, and the search for best sites has led to the construction of observatories at remote locations, including recent initiatives on the high plateaus of E Antarctica where the calm, dry and cloud free conditions during winter are recognized as amongst the best. Site selection is an important phase of any observatory development project, and candidate sites must be tested with specialized equipment, a process both time consuming and costly. A potential screening of site locations before embarking on field testing is through the use of climate models. Here, we describe the application of the Polar version of the Weather Research and Forecast (WRF) model to the preliminary site suitability assessment of an unstudied region in W Antarctica. Numerical simulations with WRF were carried out for the winter of 2011 at 3 km and 1 km spatial resolution over a region centered on the Ellsworth mountain range. Comparison with observations of surface wind speed and direction, temperature and specific humidity at nine automatic weather stations indicate that the model succeed in capturing the mean and time variability of these variables. Credible features shown by the model include zones of high winds over the southernmost part of the Ellsworth Mntns, a deep thermal inversion over the Ronne-Fincher Ice Shelf and strong west to east moisture gradient across the entire study area. Comparison of simulated cloud fraction with a spacebourne Lidar climatology indicates that the model may underestimate cloud occurrence, a problem that has been noted in previous studies. A simple scoring system was applied to reveal the most promising locations. The results of this study indicate that the WRF model is capable of providing useful guidance during the initial site selection stage of project development.
... 11 Assessments of the Arctic as being also appropriate for astronomy came only after 2002 1213 , 14 based on satellite or radiosonde data. Site testing in the High Canadian Arctic, based on ground observations, confirmed its excellent potential 15 at high elevations. 16 Optical stellar observations at ice-level in Antarctica, or at sea-level in the Arctic, are especially difficult. ...
We describe our seven year experience and the specific technical and environmental challenges we had to overcome while operating a telescope in the High Arctic, at the Eureka Weather Station, during the polar winter. The facility and the solutions implemented for remote control and maintenance are presented. We also summarize the observational challenges encountered in making precise and reliable star-photometric observations at sea-level.
... Climate data for Eureka can be found at Environment Canada (2013). Average temperatures range from −38.4˚C (1971( -2000 in winter, with a record low of −55.3˚C on 15 February 1979, to +5.7˚C (1971 -2000 July average) in summer, with a record high of +20.9˚C on 14 astronomical telescope, and several studies on optical properties of the atmosphere at night are in progress (Steinbring et al., 2010). ...
... In the winter of 2010 -11, astronomers at the Herzberg Institute for Astrophysics installed instrumentation at the PRL to evaluate the suitability of the site for a polar astronomical telescope. The results (Steinbring et al., 2010(Steinbring et al., , 2012 have been extremely encouraging, with the "seeing" over the PRL shown to be comparable to some of the best international telescope sites. Other examples of co-operative research are support of seismographic instrumentation, ionosondes through the Canadian High Arctic Ionospheric Network (CHAIN; Jayachandran et al., 2009), and logistical support for activities in support of the UN Convention on the Law of the Sea (UNCLOS). ...
... The geographic zones of interest for astronomy are those that are both dry and offer a large number of cloud-free nights. 3 With the exemption of the polar regions, where the dryness of the atmosphere results from the extremely low temperatures [4][5][6] and the Clausius-Clapeyron relationship; several other regions, dominated by high pressure centers with the subduction of relatively dry air, have been found to meet the conditions for the deployment of astronomical facilities (see Ref. 3 and 7). In these geographic areas water vapor typically decreases with altitude, and consequently the higher the location the drier the air (see Figure 8 in Ref. 8), but also the colder due to adiabatic expansion of the troposphere that gives rise to a temperature lapse rate of about-6.5 K/km. ...
The Thirty Meter Telescope (TMT) and the European Extremely Large Telescope
(E-ELT) site testing teams have recently finalized their site testing studies.
Since atmospheric water vapor is the dominant source of absorption and
increased thermal background in the infrared, both projects included
precipitable water vapor (PWV) measurements in their corresponding site testing
campaigns. TMT planned to monitor PWV at the sites of interest by means of
using infrared radiometers. Technical failures and calibration issues prevented
them from having a sufficiently long PWV time-series to characterize the sites
using this method. Therefore, for the sites in Chile TMT used surface water
vapor density measurements, which taken together with an assumed water vapor
scale height, allowed for the estimation of PWV. On the other hand, the E-ELT
team conducted dedicated PWV measurement campaigns at two of their observatory
sites using radiosonde soundings to validate historical time-series of PWV
reconstructed by way of a spectroscopic analysis of astronomical standard
sources observed at the La Silla and the Paranal sites. The E-ELT also
estimated the median PWV for the Armazones site from extrapolation of their
Paranal statistics accounting for the difference in elevation between the two
places; and also from archival analysis of radiosonde data available from the
city of Antofagasta by integration of the humidity profile starting from 3000 m
altitude. In the case of the Armazones site, the published median of PWV by
both groups differ by about 1 mm with the E-ELT values being drier than those
estimated by the TMT group. This work looks at some of the reasons that could
explain this difference, among them the water vapor scale height, the
horizontal variability of the water vapor field, and an unaccounted correction
due to a dry bias known to affect the radiosondes relative humidity sensors.
Organophosphate esters (OPEs) have been used as flame retardants, plasticizers, and anti-foaming agents over the past several decades. Of particular interest is the long range transport potential of OPEs given their ubiquitous detection in Arctic marine air. Here we report 19 OPE congeners in ice cores drilled on remote icefields and ice caps in the Canadian high Arctic. A multi-decadal temporal profile was constructed in the sectioned ice cores representing a time scale spanning the 1970s to 2014-16. In the Devon Ice Cap record, the annual total OPE (∑OPEs) depositional flux for all of 2014 was 81 μg m-2, with the profile dominated by triphenylphosphate (TPP, 9.4 μg m-2) and tris(2-chloroisopropyl) phosphate (TCPP, 42 μg m-2). Here, many OPEs displayed an exponentially increasing depositional flux including TCPP which had a doubling time of 4.1 ± 0.44 years. At the more northern site on Mt. Oxford icefield, the OPE fluxes were lower. Here, the annual ∑OPEs flux in 2016 was 5.3 μg m-2, dominated by TCPP (1.5 μg m-2) but also tris(2-butoxyethyl) phosphate (1.5 μg m-2 TBOEP). The temporal trend for halogenated OPEs in the Mt. Oxford icefield is bell-shaped, peaking in the mid-2000s. The observation of OPEs in remote Arctic ice cores demonstrates the cryosphere as a repository for these substances, and supports the potential for long-range transport of OPEs, likely associated with aerosol transport.
Nighttime zenith sky spectral brightness in the 3.3 to 20 micron wavelength region is reported for an observatory site nearby Eureka, on Ellesmere Island in the Canadian High Arctic. Measurements derive from an automated Fourier-transform spectrograph which operated continuously there over three consecutive winters. During that time the median through the most transparent portion of the Q window was 460 Jy/square-arcsec, falling below 32 Jy/square-arcsec in N band, and to sub-Jansky levels by M and shortwards; reaching only 36 mJy/square-arcsec within L. Nearly six decades of twice-daily balloonsonde launches from Eureka, together with contemporaneous meteorological data plus a simple model allows characterization of background stability and extrapolation into K band. This suggests the study location has dark skies across the whole thermal infrared spectrum, typically sub-200 micro-Jy/square-arcsec at 2.4 microns. That background is comparable to South Pole, and more than an order of magnitude less than estimates for the best temperate astronomical sites, all at much higher elevation. Considerations relevant to future facilities, including for polar transient surveys, are discussed.
The Earth's polar regions offer unique advantages for ground-based astronomical observations with its cold and dry climate, long periods of darkness, and the potential for exquisite image quality. We present preliminary results from a site-testing campaign during nighttime from October to November 2012 at the Polar Environment Atmospheric Research Laboratory (PEARL), on a 610-m high ridge near the Eureka weatherstation on Ellesmere Island, Canada. A Shack-Hartmann wavefront sensor was employed, using the Slope Detection and Ranging (SloDAR) method. This instrument (Mieda et al, this conference) was designed to measure the altitude, strength and variability of atmospheric turbulence, in particular for operation under Arctic conditions. First SloDAR optical turbulence profiles above PEARL show roughly half of the optical turbulence confined to the boundary layer, below about 1 km, with the majority of the remainder in one or two thin layers between 2 km and 5 km, or above. The median seeing during this campaign was measured to be 0.65 arcsec.
We report the first measurements of 225 GHz atmospheric opacity at Summit Camp (Latitude 72°.57 N; Longitude
38°.46 W; Altitude 3250 m) in Greenland and the Polar Environment Atmospheric Research Laboratory
(PEARL: Latitude 80°.05 N; Longitude 86°.42 W; Altitude 600 m) in Northern Canada with a tipping radiometer.
Summit Camp and PEARL are research stations mostly interested in meteorology and geophysics, and
they are potentially excellent sites for astronomical observations at sub-millimeter wavelength. We purchased
a tipping radiometer from Radiometer Physics GmbH. After a test run at the summit of Mauna Kea, Hawaii,
the radiometer was deployed to PEARL in February 2011, and relocated to Summit Camp in August 2011. The
atmospheric opacity has been monitored from February 14th to May 10th, 2011 at PEARL and since August
2011 at Summit Camp. The median values of the measured opacity at PEARL ranged from 0.11 in February to 0.19 in May; Summit Camp varied in the range from 0.04 to 0.18 between August 2011 and May 2012. Summit
Camp in Greenland is expected to be an excellent site for sub-millimeter and Terahertz astronomy, and we plan
to set up there a 12-m telescope for VLBI and single-dish observations.
The Chinese Small Telescope ARray (CSTAR) is a group of four identical, fully
automated, static 14.5 cm telescopes. CSTAR is located at Dome A, Antarctica
and covers 20 square degree of sky around the South Celestial Pole. The
installation is designed to provide high-cadence photometry for the purpose of
monitoring the quality of the astronomical observing conditions at Dome A and
detecting transiting exoplanets. CSTAR has been operational since 2008, and has
taken a rich and high-precision photometric data set of 10,690 stars. In the
first observing season, we obtained 291,911 qualified science frames with
20-second integrations in the i-band. Photometric precision reaches about 4
mmag at 20-second cadence at i=7.5, and is about 20 mmag at i=12. Using robust
detection methods, ten promising exoplanet candidates were found. Four of these
were found to be giants using spectroscopic follow-up. All of these transit
candidates are presented here along with the discussion of their detailed
properties as well as the follow-up observations.
SCAR, the Scientific Committee on Antarctic Research, is, like the IAU,
a committee of ICSU, the International Council for Science. For over 30
years, SCAR has provided scientific advice to the Antarctic Treaty
System and made numerous recommendations on a variety of matters. In
2010, Astronomy and Astrophysics from Antarctica was recognized as one
of SCAR's five Scientific Research Programs. Broadly stated, the
objectives of Astronomy & Astrophysics from Antarctica are to
coordinate astronomical activities in Antarctica in a way that ensures
the best possible outcomes from international investment in Antarctic
astronomy, and maximizes the opportunities for productive interaction
with other disciplines. There are four Working Groups, dealing with site
testing, Arctic astronomy, science goals, and major new facilities.
Membership of the Working Groups is open to any professional working in
astronomy or a related field.
