Characterizing Updraft and Plume Properties Spanning the FIREX-AQ and CalFiDE Field Campaigns

Natural disasters, including wildland fires, are becoming increasingly prevalent in densely populated areas and are responsible for population displacement, disruptions to the economy, and loss of property and life. A concerted effort to address how we respond to natural disasters as they unfold in real-time is currently underway, and is actively being pursued by multiple institutions spanning government and academia. The 2019 Fire Influence on Regional to Global Climates and Air Quality (FIREX-AQ) campaign is a testament to the synergistic interaction that has informed research-to-operations (R2O) through collective data gathering strategies over wildland and agricultural fires, which have been examined from the point of view of air quality and atmospheric dynamics in order to improve the representation of emissions, transport, and fire behavior across scales. More recently, the 2022 California Fire Dynamics Experiment (CalFiDE) targeted several rapidly evolving fires in California and Oregon to understand key modeling questions related to plume rise, wildfire spread and coupled dynamics, and in-plume chemistry evolution.

The intention of conducting these kinds of efforts, which feature "super observations", is to spatiotemporally map wildland fires to quantify processes not resolved in air quality models and to improve the understanding of coupled feedbacks when modeling wildfire spread. Unlike FIREX-AQ, which featured only remote sensing and in situ measurements aboard the NOAA Twin Otter, CalFiDE featured measurements of wildland fire behavior that included mobile ground-based remote sensing platforms using a Doppler wind lidar and two separate radars to probe the inflow structure and plume morphology, respectively. In addition, targeted sampling strategies to revisit the dynamics along the fire front were utilized in CalFiDE to study key impacts associated with the role of the background wind on rapid plume development and wildfire spread -- a component that had lacked during FIREX-AQ. The aim of this study is to therefore showcase key examples of wildland fire dynamics spanning the FIREX-AQ and CalFiDE campaigns and to demonstrate the synergy specifically between the airborne and ground-based mobile lidar systems in CalFiDE not present in FIREX-AQ.

For FIREX-AQ, a case study illustrating a tilted and advected plume will be presented with estimates of sensible heat fluxes from the source using a commonly used bentover plume rise formulation. Additionally, an examination of the plume structure across different different flight legs as well as the in-plume velocity characteristics will be shown. Following will be an analysis of the Rum Creek fire sampled during CalFIDE, which featured a rapidly evolving plume immersed in a background flow forced by a land-sea contrast in form of a marine boundary layer intrusion. An examination of the updraft characteristics from the Doppler wind lidar aboard the Twin Otter will be included alongside the mesoscale evolution of the marine intrusion as captured by the ground-based mobile Doppler lidar system. For the updraft characteristics, a technique developed to study updraft characteristics during FIREX-AQ will be used. Lastly, a preliminary analysis of the Mosquito fire will be given with a focus on rapid development during which the horizontal wind structure was augmented within the vicinity of the wildfire plume.

The results of this study represent the initial steps toward a more comprehensive analysis to address wildland fire dynamics and coupled feedbacks that sometimes plague the efficacy of models. It is the goal to not only address remaining issues pertinent to the modeling community and to determine what other measurements are needed to further improve our understanding of fireline and plume dynamics, but to also showcase the versatility of using a Doppler wind lidar to study wildland fire behavior.