Vertical structure of low-level atmosphere over the southeast Indian Ocean fronts

Abstract

During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmospheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristics along the cruise are studiedbased on in-situ observation. The observations reveal that vertical distributions of the low-level wind field and air temperature fieldon both sides of the Subantarctic Front are very different. A stronger (weaker) vertical gradient is on the cold (warm) side, whichdemonstrates that the mid-latitude ocean-atmosphere interaction is active in the southeast Indian Ocean frontal region. A low-leveljet is observed over the Subantarctic Front, with speed up to 14 m·s -1 . For the Antarctic polar front, low-level wind speed near thesea surface is greater than that aloft, in contrast with the situation of the Subantarctic Front. Comparing satellite remote sensingdata and widely-used reanalysis datasets with our in-situ observations, differences of varying magnitudes are found. Air temperature from Atmospheric Infrared Sounder (AIRS) data has a limited difference. The European Center for Medium Range WeatherForecasts Interim Re-Analysis (ERA Interim) dataset is much more consistent with the observations than the National Centers forEnvironmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1 in the southeast Indian Oceanfrontal region.