Abstract: GPS radiosondes were launched to detect the vertical structure of the atmosphere over the southeast Indian Ocean fronts region during the 25th Chinese Antarctic Expedition. Characteristic regarding the vertical profiles of the atmospheric variable along the cruise are studied. The in-situ observations reveal that the vertical distributions of the low level wind field and the air temperature on both sides of the subantarctic front are quite different. Stronger (weaker) vertical gradient appears on the cold (warm) side, which demonstrates that the mid-latitude ocean-atmosphere interaction is also active in the southeast Indian Ocean fronts region. A low-level jet is observed over the subantarctic front with the speed up to 14m/s. For the Antarctic polar front, the low level wind speed near sea surface is larger than the aloft one, which is distinct to the situation of the subantarctic front. Compared to the widely used reanalysis and satellite remote sensing datasets, it is found that ERA Interim dataset is more consistent with the in-situ observation than NCEP/NCAR Reanalysis 1, and AIRS datasets has the quite good consistence with the observation over the southeast Indian Ocean region.

Key words: Subantarctic Front, Antarctic polar front, wind speed, air temperature