资源环境科技发展态势分析平台

We identify areas near the East Antarctic ice divide where <-90 degrees C surface snow temperatures are observed in wintertime satellite thermal-band data under clear-sky conditions. The lowest temperatures are found in small (<200km(2)) topographic basins of similar to 2m depth above 3,800m elevation. Approximately 100 sites have observed minimum surface temperatures of similar to-98 degrees C during the winters of 2004-2016. Comparisons of surface snow temperatures with near-surface air temperatures at nearby weather stations indicate that similar to-98 degrees C surfaces imply similar to-944 degrees C 2-m air temperatures. Landsat 8 thermal band data and elevation data show gradients near the topographic depressions of similar to 6 degrees Ckm(-1) horizontally and similar to 4 degrees Cm-1 vertically. Ultralow temperature occurrences correlate with strong polar vortex circulation. We discuss a conceptual model of radiative surface cooling that produces an extreme inversion layer. Further cooling occurs as near-surface cold air pools in shallow high-elevation topographic basins, moderated by clear-air downwelling radiation and heat from subsurface snow.

Plain Language Summary The lowest measured air temperature on Earth is -89.2 degrees C (-129F) on 23 July 1983, observed at Vostok Station in Antarctica (Turner et al., 2009, ). However, satellite data collected during the Antarctic polar night during 2004-2016 reveal a broad region of the high East Antarctic Plateau above Vostok that regularly reaches snow surface temperatures of -90 degrees C and below. These occur in shallow topographic depressions near the highest part of the ice sheet, at 3,800 to 4,050-m elevation. Comparisons with nearby automated weather stations suggest that air temperatures during these events are near -944 degrees C or about -138F. Ultracold conditions (below -90 degrees C) occur more frequently when the Antarctic polar vortex is strong. This temperature appears to be about as low as it is possible to reach, even under clear skies and very dry conditions, because heat radiating from the cold clear air is nearly equal to the heat radiating from the bitterly cold snow surface.