Title: Understanding the Role of Convection on Global Land-Atmosphere Coupling and Remote Control of Amazonian Hydroclimate by the Andes
Abstract: This dissertation aims to better understand the role of moist convection (clouds and turbulence) in the complex dynamic coupling that occurs between components (land and atmosphere) as well as between subregions (Andes and Amazon) of the Earth system, using modern numerical modeling approaches. First, climate model representation of land-atmosphere coupling is compared between standard techniques that use conventionally parameterized convection versus prototype next-generation simulations that can include explicit convection. That is, numerical experiments are designed to isolate the global hydrologic land-atmosphere coupling on weekly-to-subseasonal and seasonal timescales using both approaches to representing convection in climate simulation. Initial analysis focuses on hydrologic coupling dynamics, and then the effects of explicit convection on thermal land-atmosphere coupling are highlighted over the southwestern U.S. and the Arabian Peninsula. Implications on global land surface Bowen ratio and its climate sensitivity are also discovered and discussed. Finally, a separate topic is analyzed, related to clarifying ongoing issues in capturing realistic regional hydroclimate over the Amazon. In this case the coupling dynamics are not between atmosphere and land, but between convective heating over a mountain chain (the Andes) and associated modulations of the atmospheric thermodynamic environment over an upstream rainforest (the Amazon). These dynamics are elucidated using mechanism denial techniques within an ensemble hindcast experiment, which sheds light on a previously underappreciated Andean control on Amazonian rainfall.