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Understanding Land-atmosphere Interactions and Their Response to Global Change by Physical Limits
Source: LASG    Viewed:  time(s)    Time: 2016-9-2
 Dr. Axel Kleidon
Max-Planck-Institute for Biogeochemistry, Germany
14:30 pm,2 September,2016
No.303,Keyan Building


The land surface-atmosphere system is highly complex, with interactions and feedbacks playing key roles in shaping the climatological state and its response to change. But what sets the limits to the magnitudes of the fluxes and the resulting interactions between the surface and the atmosphere? In this talk, I use the laws of thermodynamics as a fundamental basis to derive the limit on how much work can be derived from the planetary radiative forcing to drive the dynamics of surface-atmosphere exchange. Applied to a simple box model of the surface-atmosphere system, this limit yields the magnitude of convective heat fluxes in the system, and thereby provides a constraint to the surface energy balance as well as the intensity of convective mass exchange and hydrologic cycling. Despite the simplicity of the model, this approach predicts a range of climatic characteristics across a range of scales surprisingly well, from the local energy partitioning measured at eddy covariance sites to the sensitivity of the global hydrologic cycle to surface warming. These results imply that Earth system processes appear to operate close to their thermodynamic limit, so that their magnitudes as well as their sensitivities can be robustly predicted. I close with a brief discussion of the implications of this approach.

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