Spatial Distribution of Generation of Lorenz’s Available Potential Energy in a Global Climate Model

Abstract

Previous studies have estimated global available potential energy (APE) and global APE generation, but no study has focused on the geographic distribution of contributions to global APE and APE generation. To obtain the information needed for this analysis, simulations were performed using the NCAR CESM1.0.4 climate model. Based on these simulation results, maps of the spatial and seasonal distribution of APE contributions and APE generation in the atmosphere were obtained from the analysis. APE is generated by processes that cool relatively cool areas or warm relatively warm areas. It was found that there are two regions of the mid- to upper troposphere that contribute primarily to APE generation: 1) the tropics, especially the western tropical Pacific, owing largely to latent heat released in the intertropical convergence zone, and 2) the polar regions, especially in the relatively cold polar night, where longwave cooling is not offset by shortwave warming. It was also found that these qualitative results are largely insensitive to the assumptions examined regarding the treatment of topography in the atmosphere. Further, the analysis was extended to calculate how APE and APE generation is changed in a 4 × CO2 climate relative to a 1 × CO2 climate. It was found that in the high-CO2 climate, APE decreased by 7.0% and APE generation decreased by 10.1%. This is consistent with expectations based on decreased equator-to-pole temperature gradients in warmer climates. The methods, results, and analysis presented here should prove useful in helping to build a better understanding of controls on atmospheric kinetic energy.

Geophysical potential for wind energy over the open oceans

“…Near-surface KE is generated because of either near-surface pressure gradients or the downgradient transport of KE along wind speed gradients from the upper levels of the atmosphere. Both of these sources are ultimately driven by gradients in diabatic heating ( 8 ). In this manner, the energy cycle within the atmosphere imposes a limit on electricity generation by wind turbines, which acts at the scale of kinetic energy extraction (KEE) rates required to meet the primary power generation demands of the 21 st century.…”

Reduced emissions through climate damage to the economy

“…Basic theory suggests that decreased equator-topole temperature differences should decrease wind speeds overall. Indeed, one idealized study (14) concluded that the generation and dissipation of atmospheric kinetic energy would decrease by ∼10% in a world with quadrupled atmospheric carbon dioxide. However, how this plays out in the utility of wind power production is yet to be determined.…”

On the Local View of Atmospheric Available Potential Energy

“…2 (e.g., Li et al 2007) or Eq. 1 (e.g., Ahbe and Caldeira 2017). Although these approaches appear to yield plausible results, it goes without saying that it would be far more satisfactory to base such analyses directly from a truly local definition of APE.…”