Discussion

The analysis of the AWS data set and the PWV measurements shows the following main results:

• DC and SP average temperatures are comparable, ranging between typical values of -65 C in winter and -26 C in summer. The median value for both sites is -53 C, while the correlation of monthly average temperatures between DC and SP is 96%.
• The pressure is always lower at DC than at the SP. Median values are 644 hPa and 682 hPa respectively. Monthly averaged pressure data show a correlation of 92 % between the two sites.
• The wind speed is very low at both sites, with a maximum speed of 15.9 m/s at DC and 18.9 m/s at SP.
• A Kolmogorov-Smirnov test shows that wind speed distributions for the two sites are different. Correlation between monthly averaged wind speed data is less than 30 %. 50th percentile values for wind speed, evaluated for the whole data set, are 1 m/s at DC and 2 m/s at SP.
• Wind azimuth distributions are different: the prevalent direction is approximately azimuth 180 at DC and between azimuth 0 and 90 at SP.
• PWV values measured at DC in January 1997 are comparable with SP values in the same season and lower than those measured at other sites.

In Table 1 and Table 2 our results for Antarctica (over eight years) are compared with a well-established observing site, Mauna Kea (Hawaii Islands) and a future important site in the Atacama desert (Northern Chile). Data for these latter sites are reported from Holdaway (1996).

Table 2: Comparison between AWS data for Antarctic sites and data for Mauna Kea (Hawaii Islands) and Atacama desert (Chile) from Holdaway 1996

Some conclusions can be derived from these results:

• Lower wind regimes at the Antarctic sites result in lower turbulence implying a smaller contamination on observations. It is worth considering that most of the sky-noise at Infra-Red and millimetric wavelengths is induced by convective motion and wind driven turbulence in the lowest layers of the atmosphere, where the bulk of water vapor is found (Smoot et al. 1987; Ade et al. 1984; Andreani et al 1990). While the former needs further investigation (Argentini 1998, Burton 1995), the latter is minimal on the Antarctic Plateau.
• Lower average wind speed reduces pointing errors for large antennas (see Holdaway, 1996).
• In terms of wind speed, DC shows better conditions with respect to SP.
• The high Antarctic Plateau is the driest observing site on Earth.
• DC and SP pressure and temperature conditions are strongly correlated, indicating that they share similar meteorological conditions. It is possible to infer that PWV values at DC during wintertime are similar to SP ones in the same season.
• 225 GHz and 492 GHz opacities for DC, calculated using a model valid for SP, show results similar to this site and better than Mauna Kea, when comparable water vapor amounts are considered.

© Copyright Astronomical Society of Australia 1997