Mesoscale features and atmospheric refraction conditions of the Arctic Marginal Ice Zone

Abstract

The Marginal Ice Zone Experiment (MIZEX-83) conducted in the Arctic during the summer of 1983 is summarized and the mesoscale features and atmospheric refraction conditions described. The three case studies examined are: warm air advection over dense pack ice causing strong elevated ducting and subrefraction, cold air advection over relatively open water causing shallow convection and normal refraction condi­tions, large scale subsidence in the western quadrants of an anticyclone leading to super-refraction and weak ducting. Developing synoptic scale cyclones adjacent to the MIZEX-83 area often determined the airflow over the region. The observed large horizontal SST gradients were the dominant forcing mechanisms on surface layer stability. Trapping layers associated with subsidence inversions can be located on satellite imagery by assuming that stratiform clouds form immediately below the inversion. Uniform cloud and refraction layers were not common during MIZEX-83 due to strong mesoscale variability. Factors affecting inversion height include subsidence and entrainment mixing. Bulk Richardson number values for locations over the open water and pack ice show significant variability in stability conditions across the MIZ.