Understanding Climate Sensitivity to Tropical Deforestation in a Mechanistic Model

Ning Zeng

An analysis is provided to explain the sensitivity of regional climate to tropical deforestation based on an intermediate-level mechanistic model for land-atmosphere interaction. The analytical framework is made possible by the fact that feedback to local thermodynamics from large scale dynamics is negligible, so the determin ing processes take place in situ. The analytical method accurately reproduces the intermediate-level numerical model results for an albedo change scenario, and further provides insight into the mechanisms. A three-way balance among large scale adiabatic cooling, moist convective heating and radiative heating allows two positive feedback mechanisms: moisture convergence feedback and evaporation feedback that give rise to the high sensitivity. The analysis also highlights a deficiency in column energy balance commonly used in tropical simple models, which results in a sensitivity likely too high. In light of these findings, some immediate needs for further advancing our understanding to the problem are discussed.