Applied Mathematics Seminar | Fredric Laliberte, A moist atmospheric heat engine perspective on the thermodynamics of climate change

Incoming and outgoing solar radiation couple with heat exchange at Earth’s surface to drive weather patterns that redistribute heat and moisture around the globe, creating an atmospheric heat engine. In this presentation, I will present a numerical procedure to project atmospheric motions onto purely thermodynamic coordinates. The procedure, inspired by finite volume methods, ensures that in a steady simulation the thermodynamic representation of atmospheric motions describes a non-divergent flow. As a consequence of this property, two-dimensional thermodynamic diagrams of the atmospheric circulation depict mostly closed cycles that can be used to understand energetic properties of the atmospheric heat engine.

To illustrate how this depiction can help gain insights into the atmospheric circulation, I will use reanalyzed observations and a climate model simulation with anthropogenic forcing to discuss how the atmospheric heat engine’s work output is likely to change in a warming climate. My analysis will be based on the principle that the work output is always less than that of an equivalent Carnot cycle and that it is constrained by the power necessary to maintain the hydrological cycle. I will present results showing that in the climate simulation the hydrological cycle increases more rapidly than the equivalent Carnot cycle, leading me to conclude that the intensification of the hydrological cycle in warmer climates might limit the heat engine’s ability to generate work. Finally, I will do an overview of other projects that I am involved in that use a similar procedure to describe the oceanic circulation.