UNDERSTANDING CLIMATE SENSITIVITY TO TROPICAL DEFORESTATION IN A MECHANISTIC MODEL

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 mad e possible by the fact that feedback to local thermodynamics from larg e-scale dynamics is negligible, so the determining processes take plac e in situ. The analytical method accurately reproduces the intermediat e-level numerical model results for an albedo change scenario and furt her provides insight into the mechanisms, A three-way balance among la rge-scale adiabatic cooling, moist convective heating, and radiative h eating allows two positive feedback mechanisms, moisture convergence f eedback and evaporation feedback, that give rise to the high sensitivi ty. The analysis also highlights a deficiency in column energy balance commonly used in tropical simple models, which results in a sensitivi ty that is likely too high. In light of these findings, some immediate needs for further advancing understanding of the problem are discusse d.