On the Local View of Atmospheric Available Potential Energy

AbstractThe possibility of constructing Lorenz’s concept of available potential energy (APE) from a local principle has been known for some time, but it has received very little attention so far. Yet the local APE density framework offers the advantage of providing a positive-definite local form of potential energy, which, like kinetic energy, can be transported, converted, and created or dissipated locally. In contrast to Lorenz’s definition, which relies on the exact from of potential energy, the local APE density theory uses the particular form of potential energy appropriate to the approximations considered. In this paper, this idea is illustrated for the dry hydrostatic primitive equations, whose relevant form of potential energy is the specific enthalpy. The local APE density is nonquadratic in general but can nevertheless be partitioned exactly into mean and eddy components regardless of the Reynolds averaging operator used. This paper introduces a new form of the local APE density that is easily c...