Romanski and Rossow 2013
, and , 2013: Contributions of individual atmospheric diabatic heating processes to the generation of available potential energy. J. Climate, 26, 4244-4263, doi:10.1175/JCLI-D-12-00457.1.
The generation of zonal and eddy available potential energy (Gz and Ge) as formulated by Lorenz (1955) are computed on a global, daily, synoptic-scale basis to consider the contribution of each diabatic heating component separately and in combination. Using global, mostly satellite-derived datasets for the diabatic heating components and the temperature enables us to obtain Gz and especially Ge from observations for the first time and at higher temporal and spatial resolution than previously possible. The role of clouds in maintaining G is investigated.
The global, annual mean Gz is 1.52 W/m2. Values reach a minimum of 0.63 W/m2 in the NH during spring, and a maximum of 2.27 W/m2 in the SH during winter. The largest contributors to Gz are latent heating in the tropical upper troposphere, associated with the ITCZ in the summer hemisphere, and surface sensible heat fluxes in the winter pole. Diabatic cooling by radiative fluxes (mostly longwave) generally destroys Gz.
Ge is negative and about an order of magnitude smaller than Gz, with a global, annual mean of -0.29 W/m2. However, the small value of Ge results from the cancellation of the contributions from the individual diabatic heating terms, which are actually roughly similar in magnitude to their Gz contributions.
The results presented herein suggest that the large scale dynamics of the atmosphere organizes the spatial and temporal distribution of clouds and precipitation in such a way as to increase the energy available to drive the circulation, a kind of positive feedback.