Land surface models are used to represent terrestrial processes that shape global climate; examples of these processes include evaporation, plant water use, and photosynthesis. While much progress has been made to improve and refine these models, some hydrological processes are not well captured, which hinders our ability to understand land-atmosphere interactions and ultimately to predict impacts of climate change on water resources. The inadequate representation of evapotranspiration may partly explain why global climate models do not match observed precipitation patterns. Multiple factors contribute to this problem. In moist tropical regions, high humidity, leaf wetness, and cloud cover combine to suppress forest water use and possibly reduce forest growth in ways that are poorly understood. Even the percentage of precipitation that is re-evaporated from tropical canopies, as opposed to being transpired, is not well established.

This new project aims to improve the modeling of fluxes of water vapor and carbon dioxide to and from tropical forests though an integrated field measurement and modeling approach. We are currently operating and expanding a micrometeorology measurement suite at our transitional tropic forest site in the Texas A&M University Soltis Center for Research and Education. In addition to quantifying carbon and water fluxes, our field efforts also focus on examining the hourly-to-daily-scale transitions between wet and dry canopy states and the weekly-to-monthly-scale transitions between the wet and dry seasons. Such data will help to better represent and parameterize processes such as canopy interception and wet canopy evaporation in land surface models of tropical forests. This paper will focus on presenting the preliminary data we have collected to date, as well as our plans for model development at the point, stand, and regional (CLM-WRF) scales. Data sharing mechanisms and synthesis of data from other Neotropical sites will also be discussed.