Identifying synoptic-scale sources of short-term (3-10 day) zonal available potential energy generation

Available potential energy (APE) is an estimate of the amount of potential energy in the atmosphere available for conversion to kinetic energy, providing a good proxy for the overall strength of the general circulation. In previous studies, estimates of total hemispheric APE, APE generation, and conversion to kinetic energy have been used to explain the annual APE cycle as well as short term APE depletion events by mid-latitude cyclones. Here, we focus instead on how APE can be built up on short time scales (3-10 days). Using a standardized-anomaly based criteria, we identify a climatology of continuous build-up events of zonal APE in the Northern Hemisphere. These are divided into two subsets based on the final value of APE anomaly, either anomalously high or neutral. Several case studies are conducted to identify synoptic features in the Northern Hemisphere general circulation that help contribute to the generation of zonal APE. These include, but are not limited to, the filling of low-latitude low pressure systems, and collapses of high-latitude high pressure systems. Using a thermodynamic budget, we further explore sources of heating and cooling in the atmosphere in association with these changes to the mass fields. By exploring the changes to the thermodynamic structure of the troposphere, we will be able to assess the roles of static stability and horizontal temperature gradients, the two contributing terms in the zonal APE equation.