EPS Colloquium – Dani Or, University of Nevada Reno, ETH Zürich, & Desert Research Institute
Surface Evaporation and Rainfall Partitioning in Arid Lands – Local and global perspectives
The presentation will explore two interconnected vignettes related to surface evaporation. In the first part we will review basic aspects of surface evaporation and discuss how soil type modulates evaporation dynamics via surface resistance and internal drainage that shelter infiltrated rainwater from evaporation losses (but not from plant water uptake). These basic elements offer a simple pathway for estimation of surface evaporation losses locally and globally. In the second part, we will focus on arid regions where rainfall is partitioned into evaporation or transpiration to develop upper bounds for plant available soil water as determined by soil properties and rainfall characteristics. We will quantify the fraction of rainwater sheltered from surface evaporation to estimate arid region vegetation carrying capacity using the surface evaporation capacitor (SEC) model. Rainwater leakage into deeper soil layers supports vegetation and inter-annual storage. Evidence from arid regions shows strong links between evaporation protected rainwater and net primary productivity (NPP) in good agreement with observations and models. Evaporation protected soil water storage increases with increasing rainfall variability (and over coarser soils) and can potentially enhance vegetation carrying capacity of arid landscapes for similar mean annual precipitation. We will discuss implications of this mechanism for changes in future rainfall characteristics, observed global greening of arid lands and as a potential driver for woody vegetation encroachment.
To be added to the EPS colloquium mailing list, please contact Caroline Carr at carolinecarr@fas.harvard.edu.
Dani Or is a research professor with the Division of Hydrologic Sciences of the Desert Research Institute in Reno, NV, USA. He is an emeritus professor of Soil and Terrestrial Environmental Physics with the Swiss Federal Institute of Technology (ETH) Zurich, Switzerland. His recent research focuses on modeling effects of wildfires on soil properties and catchment hydrology and on quantifying soil structure in natural and managed systems. His research focuses on mass and energy transport in porous media; mechanics of landslides and avalanches; evaporation from porous surfaces, and on biophysical processes and biological activity in soil. Dr. Or has authored and coauthored over 340 ISI publications, co-authored a book, and over 500 proceeding papers and abstracts. Dr. Or is the former Editor in Chief of the Vadose Zone Journal, recipient of the Kirkham Soil Physics Award (2001), 2004 Fellow of the Soil Science Society of America, Chair of the 2008 Gordon Research Conference on Flow and Transport, and 2010 Fellow of the American Geophysical Union. He was selected 2013 Birdsall-Dreiss distinguished lecturer; recipient of Helmholtz International Fellow Award (2013); 2014 Fellow of Geological Society of America; the 2017 recipient of the European Geosciences Union Dalton Medal, the 2018 AGU Langbein lecturer, and recently elected to the National Academy of Engineering 2022.