Airborne L-Band Radiometer Mapping of the Dome-C Area in Antarctica

A 350 km × 350 km area near the Concordia station on the high plateau of Dome-C in Antarctica has been mapped by an airborne L-band radiometer system. The area was expected to display a rather uniform brightness temperature (TB) close to the yearly mean temperature-well suited for calibration checks for spaceborne instruments like SMOS, Aquarius, and SMAP. The measured TBs show unexpected variations like 8-K variation over 240 km on an east-west profile through Concordia, and in certain local cases, a slope of about 0.7 K/km. Comparing the measured TB map with bottom topography reveals a convincing correlation. Simulations show that variations in bedrock topography can indeed modulate the TB appropriately to explain the observed variations. It is concluded that use of the Dome-C area for calibration check of spaceborne radiometers is indeed viable, but with caution-especially when comparing instruments with different spatial resolutions.