Balanced Dynamics and Cyclone-Anticyclone Asymmetry

University Of Washington, Seattle WA

Investigators

Abstract

This project will investigate the dynamics associated with the cyclone-anticyclone asymmetry, namely, why cyclones tend to have larger amplitude and isolated cores in comparison to weaker and broader anticyclones. The research will be based on an idealized theoretical framework that is valid an order beyond the quasigeostrophic (QG) model in the Rossby number expansion, i.e., the QG+1 system. The PI will extend his prior study on the QG+1 system that has the tropopause as a boundary to include, in addition, a rigid-surface as another boundary to have two boundaries in the system (thus named a 2sQG+1 system). The PI will test the hypothesis that the control parameter of the 2sQG+1 system is the distance between the two boundaries in that it would regulate the relative importance of baroclinic and barotropic dynamics. The second hypothesis to be tested is that the 2sQG+1 system will show that cyclones have a weaker energy transfer to larger scales and thus will maintain robust structures confined to the boundaries, whereas anticyclones, which have a strong upscale energy transfer, will span the troposphere. These hypotheses serve to provide explanations of the cyclone-anticyclone asymmetry in nature. The idealized theoretical modeling work will then be tested with the National Center for Environmental Prediction (NCEP) analysis data using the statistics of polar lows. The results have the potential of improving our understanding of scale interactions between baroclinic and barotropic dynamics, and nature of cyclone-anticyclone asymmetry. The planned research will provide good educational opportunities for graduate studies.