Event Date
The traditional motivation behind studying the dynamics of turbulent wind flow in vegetation canopies has been to understand the nature of mass, momentum, and energy exchange between the land surface and the atmosphere. The nature of this interaction determines the microclimate in a forest environment where plants exchange carbon and water and its understanding is relevant for a plethora of applications ranging from ecology, hydrology, agriculture, and the modeling of weather and climate. However, the fundamental nature of turbulence in a vegetation canopy is significantly different from the atmospheric surface layer lying above, which means that scaling laws and exchange coefficients from traditional wallbounded flows are not applicable. In a forest canopy, momentum absorption happens not only at the ground surface but throughout the depth of the canopy, resulting in a unique ‘roughness sub layer’. Instead of a log-layer, the mean velocity profile is inflected, second-order moments are variable with height and skewnesses are large. Large-scale coherent structures impart a significant impact on turbulence dynamics. Sweeping motions arising out of downdraft motions of counter-rotating vortices dominate eddy fluxes. A mixing layer model is found to be a better model for describing canopy flows. High-frequency measurements and computational fluid dynamics modeling, especially Large Eddy Simulations (LES) have been instrumental in revealing the nature of canopy turbulence in the last few decades. Now this knowledge is being used to advance our limited understanding of how wildland fires behave. The main controls on wildland fire behavior – fuel (canopy and grasslands), weather, and topography are strongly influenced by the fine-scale physics of canopy turbulence. We will demonstrate that further developments in the understanding of canopy turbulence can benefit wildfire modeling tools and develop actionable management strategies.
Speaker Bio
Dr. Tirtha Banerjee is an Associate Professor at the Department of Civil and Environmental Engineering, University of California, Irvine. He received his B.S. degree in Civil Engineering from Jadavpur University (Calcutta, India) in 2011 and his Ph.D. in Environmental Science from Duke University (Durham, NC, USA) in 2015. After conducting postdoctoral research at Karlsruhe Institute of Technology (KIT) in Germany and Los Alamos National Lab (NM, USA) as a Chick Keller Postdoctoral Fellow in climate science and subsequently, as a Director’s Fellow in atmospheric sciences, he joined UC Irvine in the fall of 2019, where he was an Assistant Professor till the fall of 2023. Research in the Boundary Layers and Turbulence (BLT) Lab led by Prof. Banerjee involves wildfires, environmental flows, and biosphere-atmosphere interaction using a range of theoretical, numerical, and experimental techniques. He leads the NSF-funded international consortium on wildfires, called iFireNet, and the UCOP-funded SPARx project aimed at transforming prescribed fire practices for California. He was recently awarded the NSF CAREER Award to conduct research on the role of turbulent fluid dynamics in wildland fire behavior. He currently serves as an Associate Editor for the journal Earth Systems and Environment (Springer) and as an editorial board member for the journals Agricultural and Forest Meteorology (Elsevier) and Scientific Reports (Nature). Prof. Banerjee also serves on the Science Advisory Panel of the Fire and Forest Resilience Task Force in the State of California.