This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Land is an integral component of the climate system and changes in land cover can significantly influence terrestrial weather and climate. This project aims to investigate regional-scale vegetation-atmosphere feedbacks over seasonal timescales in the context of deforestation in Rondonia, a Brazilian state in southwestern Amazonia.
Deforestation along highways and secondary roads has created a unique "fishbone" pattern that forces organized mesoscale circulations similar to sea-breezes, often referred to as "vegetation breezes." These vegetation breezes affect local hydrometeorology, enhancing cumulus clouds and convective precipitation over the deforested patches. This project will test the hypothesis that deforestation in Rondonia exerts a negative feedback on itself via the atmospheric pathway. The hydrometeorological effects of fishbone deforestation are most prominent during the dry and transition seasons when excess rainfall can enhance plant growth over deforested regions. This constitutes a negative feedback because accelerated vegetation recovery over deforested patches partially compensates for the effects of deforestation. This project will also study the role of background hydrometeorology in the vegetation-atmosphere feedback process. In particular, it will investigate if the system exhibits threshold behavior, i.e., whether the response to deforestation can switch from a negative (self-healing) to a positive (runaway) feedback if the background temperature, precipitation and cloud cover exceed certain threshold values. Sensitivity studies will be conducted with a plant growth model to estimate the magnitudes of these thresholds, if present.
This will be among the first studies on vegetation-atmosphere mesoscale feedbacks in the coupled biosphere-atmosphere system over an intermediate scale - regional in space and seasonal in time, thereby filling the spectral gap between the turbulence and climate scales. The project will support and train a Ph.D student and also an undergraduate intern to develop the java-version of the dynamic vegetation model. This model will be used as a hands-on tool in a course for students to conduct simple numerical experiments and explore key processes driving biosphere-atmosphere interactions. It will contribute to the research and teaching curriculum of the new Undergraduate Major in Atmospheric Sciences starting in the fall of 2008 at the University of Illinois.
