Mesoscale Exchange of Vortex Ai

Investigation Description: The processes which control the transport of air into and out of the lowermost regions of the polar vortex during winter are still not fully understood. Mixing estimates contain substantial errors, perhaps because the ubiquitous occurrence of vertically-narrow layers in the tracer fields (laminae in one dimension; tracer sheets in two-dimensions) along the vortex boundary, which are too small to be adequately represented by atmospheric models, are playing a significant role in the exchange of vortex and extra-vortex air (Reid et al., 1998). Tracer laminae are present throughout the winter, their numbers maximizing between 14 and 17km at the vortex boundary during February. Aircraft, satellite and balloon-borne data will be employed to study the mesoscale exchange of air across the polar vortex boundary in the form of tracer laminae. The co-location of measurements from a number of different platforms will allow, for the rst time, simultaneous observations of these features in two dimensions. The tracer, pressure and temperature profiles from SAGE III, if available, will provide valuable supplementary information in the regions where the aircraft flies, as well as elsewhere along the vortex boundary. The meteorological conditions prevalent during these observations will be used to initialize the University Corporation for Atmospheric Research (UCAR) mesoscale model, version 5 (MM5), to help identify the nature of the exchange mechanism(s).