The Budget of Local Available Potential Energy of Low-Frequency Eddies in Northern Hemispheric Winter

Abstract Low-frequency (LF) transient eddies (intraseasonal with time scales longer than 10 days) are increasingly found to be important in large-scale atmospheric circulation, high-impact climate events, and subseasonal-to-seasonal forecasts. In this study, the features maintenance of available potential energy LF (LF EAPE), which denote temperature fluctuations, have been investigated. Our study shows that wintertime EAPE, greater amplitude extensively studied high-frequency (HF) eddies, exhibits distinct horizontal vertical structures. Different from HF whose action centers over midlatitude oceans, EAPE is most active continents midlatitudes, as well subpolar region shallower structure. By diagnosing derived budget we find that, strong background gradient mid- high-latitude (e.g., coast regions along Greenland, Barents, Kara Seas), baroclinic generation major source EAPE. The generated transported downstream southward via flow. also dissipated by damped diabatic effects, converted EKE motions. above budget, together barotropic dynamics revealed previous works, suggests multiple sources thus complicated variabilities.