Local wave activity budgets of the wintertime Northern Hemisphere: Implication for the Pacific and Atlantic storm tracks

A recently developed finite-amplitude local wave activity (LWA) diagnostic framework quantifies eddy-mean flow interaction on regional scales. Here we examine the column budgets of LWA for the winter Northern Hemisphere with the European Centre for Medium-Range Weather Forecasts ERA-Interim product, with an eye toward quantifying the maintenance and variability of the Pacific and Atlantic storm tracks. The budget is governed by (i) low-level meridional eddy heat flux, (ii) horizontal convergence of the LWA flux, and (iii) nonconservative (diabatic) sources-sinks. In both regions, the low-level meridional heat flux fuels LWA on seasonal timescales but the zonal LWA flux convergence and diabatic effects dominate the synoptic variability. Cospectral analysis shows that the interplay between barotropic zonal wind and column-averaged LWA through the meridional eddy momentum flux convergence is significant over the Pacific but not the Atlantic. A first attempt at partitioning LWA into stationary and transient eddy contributions is also discussed.