Liviu Ivanescu, ESO (firstname.lastname@example.org)
about the quality of the poles for astronomical observations are very recent
and only at the South Pole. There, the quality of the seeing at only 100-200
meters elevations was found to be much better than anywhere else. More, there
are new infrared windows to the sky. In
The quality of a particular site for astronomical purpose may be affected by access facility or by different interests to economically develop some remote areas. However, it focuses mostly on the environment quality: meteorological and earthquakes parameters. The last ones are not a big issue as long they are in normal range. The most important are the atmosphere characteristics which affect the quality of astronomical images by the transparency of the sky (less transparency, more noisy images) and by the turbulence (more turbulence, less angular resolution). Some of the most important meteorological parameters laying in the first category are: cloud amounts; cloud opacity; clouds altitude (to know what happens at different elevations); absolute humidity; visibility; aerosols (haze); precipitations; precipitable water vapor (this changes the observational parameter known “air mass”); aurora. For the second category one may note: wind speed; gust speed; wind speed variations; wind direction variations; wind, pressure and temperature altitude profiles; temperature variations. One should note that all this parameters are most significant close to the ground level. The easiest way to get out of them is to put astronomical observatories on the top of the mountains. For this reason one starts with some topographic considerations and then a meteorological analysis.
atmosphere is thicker at the equator and thinner at the poles. One may expect
that the ground problematic layers of the atmosphere are even closer to the
ground too. In this way, even relatively low elevations near the poles become
interesting. The Figure 1 shows a map of the surrounding topography of the
North Pole. One may see that the northern
Figure 1 North Pole topography
Figure 2 Relief of
Figure 5 View from
Figure 6 View from
Figure 8 Second highest peak
(1898 m) in
Figure 9 Accessibility
Figure 10 Camps and Supply stations
significant feature of the northern polar night, which is important for
astronomy, is a massive radiation inversion. This is a stable and deep feature
which calms down most the meteorological activity. At the
The sites of interest here are close to the magnetic North Pole, in the center of the auroral oval (Figure 11). The brightness of the aurora is therefore a minor observational issue.
the winter the ice in the
The arctic haze, which is an important amount of aerosols coming from Eurasian industrial areas, is clearly seen in this clean environment. It has an optical depth of 0.1 at most (referenced to vertical, at 500 nm) and it’s observed especially in late winter, early spring months. The wavelength dependence is about 1 over lambda. The haze is primarily below 1 km altitude, though one finds occasionally bands up to 5 km. Moreover, this is present mostly along the costal borders. The Barbeau peak should not experience any such contamination.
In general poor visibility occurs more often in summer because of the more frequent occurrences of the fog at low elevations. Poor visibility commonly occurs at higher elevations just prior to the beginning of the melt. This is due to the blowing of the uncompacted snow available in that period. To avoid such thing it may be possible to remove the small quantity of multi-secular snow over the peak.
Near the North Pole one finds too a diminished ozone concentration, by 10 to 40% in some areas. This may eventually allow ultra-violet astronomical observations.
The atmospheric water vapor makes important absorptions of the light, mostly in infrared. As this parameter is not very significant in the Artic winter, new infrared windows are opened for astronomy. Extremely, this water vapor allows clouds formation too, associated obviously with a very important opacity effect. A first indirect indication of this basic parameter and its effects is getting from the precipitations statistics.
The Astronomical Polar Night is a period of the arctic
winter north of 84°33'N, when horizon during astronomical twilight. The Nautical Polar Night
is a period of the arctic winter north of 78°33'N, when the most light is a
faint glow in the southern sky, but it is impossible for an observer to make
out any horizon. Alert and
known that good astronomical sites are at high elevations, slightly inside the
land (as the Chilean border) or inside islands (
Form a large
scale statistical point of view, the northern Canadian islands, including the
Figure 11 Auroral oval
Figure 12 Mean arctic precipitations in February (from Arctic Meteorology and Climate Atlas)
Satellite data analysis
The raw data was recorded with AVHRR (Advanced Very High Resolution Radiometer) satellite sensor carried on NOAA polar-orbiting satellites, at and Local Time (LT), from 1982 to 1999. There are three different data sets, at 1.25, 5 and 25 Km resolutions. The atmospheric parameters where then retrieved by post-processing (CASPR program) and they are available as monthly means with 25 Km resolution at:
http://stratus.ssec.wisc.edu/products/appx/. The algorithms used to obtain the results are explained there as well.
On a 25 Km grid, the atmospheric parameters for sharp high peaks are averaged out. On a future step, I will compute clear sky chart at 1.25 Km resolution as well. For the present study I considered only the data at LT, for January (winter) and July (summer).
The “clear sky” means percentage of time with no clouds of any kind, including cirrus. This is what we call a “photometric sky”. The “mm precipitable water” is a vertical column of precipitable water vapor present in the atmosphere, expressed in millimeters. The spatial resolution here is lower. The “surface temperature C” is expressed in degrees Celsius (C).
As a comparison, in Paranal there are actually 76% photometric nights (averaged all over the year), while the precipitable water vapor is 1.5 mm in the winter (in the summer is more).
Figure 13 Winter atmospheric conditions in the Arctic
Figure 14 Summer atmospheric conditions in the Arctic