  We present low-resolution turbulence profiles of the atmosphere above Dome C,
Antarctica, measured with the MASS instrument during 25 nights in March-May
2004. Except for the lowest layer, Dome C has significantly less turbulence
than Cerro Tololo and Cerro Pachon. In particular, the integrated turbulence at
16 km is always less than the median values at the two Chilean sites. From
these profiles we evaluate the photometric noise produced by scintillation, and
the atmospheric contribution to the error budget in narrow-angle differential
astrometry. In comparison with the two mid-latitude sites in Chile, Dome C
offers a potential gain of about 3.6 in both photometric precision (for long
integrations) and narrow-angle astrometry precision. These gain estimates are
preliminary, being computed with average wind-speed profiles, but the validity
of our approach is confirmed by independent data. Although the data from Dome C
cover a fairly limited time frame, they lend strong support to expectations
that Dome C will offer significant advantages for photometric and astrometric
studies.
