Title: Improvements to and applications of remotely sensed evapotranspiration
Abstract: Evapotranspiration (ET) is a key climate variable that links the water, carbon, and energy cycles. Remote sensing ET models facilitate studying land-atmosphere feedbacks, benchmarking earth system models, and quantifying the human impact on the terrestrial water cycle. In this dissertation defense, I will discuss advancements to and applications of satellite-driven ET models through the lenses of the surface energy budget, the water cycle, and the carbon cycle. First, I analyze the role of ground heat flux in remote-sensing ET models. I identify the best ground heat flux model, discuss the mechanisms that control this flux, and quantify the impact of ground heat flux uncertainty on modeled ET. Second, I improve the Priestley-Taylor Jet Propulsion Laboratory ET model by integrating soil moisture observations from the Soil Moisture Active Passive (SMAP) mission. This is the first global remote sensing ET dataset to incorporate water availability limitations from SMAP. The new modeled ET estimates reveal the most improvement in water-limited regions. Finally, I link the carbon and water cycles from space with observations of solar induced fluorescence (SIF) from the Orbiting Carbon Observatory 2 (OCO-2) and the SMAP-based ET dataset. I apply these datasets to characterize vegetation stress across four regions in response to increases in temperature and decreases in water availability.