The hydrologic observation, model, and theory congruence on evapotranspiration variance: Diagnosis of multiple observations and land surface models

Department of Hydrology and Atmospheric Sciences
Weekly Colloquium

Thursday, March 19, 2020
4 pm via Zoom, No In-Person Meeting
Zoom Socializing Before Talk ~ 3:30 to 4:00 pm & After Talk ~ 5:00 to 6:00 pm
Ruijie Zeng
Assistant Professor, School of Sustainable Engineering and the Built Environment
Arizona State University


Our observation and modelling capabilities for understanding large scale terrestrial evapotranspiration (ET) have advanced in last decades. However, there are still discrepancies between remotely sensed products and land surface models (LSMs), and both cannot be directly validated. We propose to reconcile the observations and simulations of ET through a diagnostic framework composed of an observation‐model‐theory triplet. The Evapotranspiration Temporal VARiance Decomposition (EVARD), a theoretical tool, is used as a benchmark to estimate and diagnose ET variance across the contiguous United States (CONUS) with datasets including hydroclimatic observations, GRACE-based terrestrial water storage, four ET observation products, and four LSMs. Five experiments are systematically designed to evaluate and diagnose possible errors and uncertainties in ET temporal variance estimated by the four observation‐based ET products and the four LSM simulations. We quantify the sources of ET variance from climate and watershed storage components, evaluate the bias and uncertainties by intercomparing multi-source, multi-variable observation products, and diagnose the possible missing processes in LSMs. This study urges advancing hydrologic knowledge by finding congruence among models, data, and theories.


Ruijie Zeng joined the School of Sustainable Engineering and the Built Environment at Arizona State Uninversity in January 2020 as an Assistant Professor. His primary area of interest is hydrologic modeling and water resources analysis. He obtained his bachelor’s degree in hydraulic engineering from Tsinghua University, China, and master’s and doctoral degrees in civil engineering from The University of Illinois at Urbana-Champaign. He works on enhancing mechanistic understanding, predictable capability, and sustainable management of watersheds.