Gabriel G. Katul
The 2018 John Dalton Medal is awarded to Gabriel G. Katul for his fundamental contributions to the theory and measurement of evapotranspiration, canopy turbulence and ecosystem fluxes.
Gabriel Katul has made major contributions in two important aspects of the hydrologic cycle, flux of water to the atmosphere through evapotranspiration and storage of water on the land surface as soil moisture. Katul has advanced the understanding of the dynamics of evapotranspiration by quantifying how evapotranspiration is driven by turbulence that occurs near the vegetation canopy.
Katul’s work has shown that the complexity of the land surface interacts with small scale meteorological conditions to generate these turbulent phenomena. In turn, these turbulent phenomena control the fluxes of water and energy between the atmosphere and the land surface, as well as influencing the cycling of carbon and nitrogen in ecosystems. Katul’s accomplishments in the area of evapotranspiration have been achieved not only through development of new theory and models, but also through definitive experimental studies. Furthermore, he and his colleagues and students have taken the important step of reducing the order of these models to allow for application of the simpler models in the interpretation of precipitation patterns and ecosystem processes.
In terms of controls on soil moisture, he and his colleagues and students have clarified the hydraulic processes occurring in plants and in soils that determine how water is stored in soil under different atmospheric conditions. His team has developed predictive equations describing gas exchange at the level of individual leaves that are being used in the further development of climate models. This work has provided new insights into the feedbacks between climate and the cycling of carbon as modulated by ecosystem primary production and respiration.
Katul has been a leader in connecting theoretical studies to field campaigns. For example, he has been active since 1996 in the Ameriflux network of tall towers that explored spatial variability in the patterns of turbulence above a forest canopy. Further, he is a leader in the experiment to determine the response of forests to enrichment of atmospheric carbon dioxide, e.g. the Free Air CO2 Experiment.
Katul has been a pioneer in developing a quantitative understanding of the interactions between soils, vegetation and climate that are driven by turbulent processes at the surface of the landscape. This fundamental work in hydrology has important applications for understanding controls on water availability around the world. Katul has also been a valued mentor for many young hydrologists and has contributed to the advancement of hydrology through his leadership.