Publication Date

Spring 2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Climate Science

Advisor

Adam Kochanski

Subject Areas

Meteorology

Abstract

In this study, the fire-induced circulations were analyzed during the FireFlux2 (FF2) experimental burn using WRF-SFIRE to directly quantify the effects of the fire on local conditions. We utilized observational data from the FF2 burn and numerical simulations to assess the impacts of fire on local micrometeorology under ∼12m/s winds. Two simulations were executed. One in a two-way coupled mode and one in a one-way coupled mode. The difference between the simulations was used to quantify the fire impacts on the circulation at the head and flanks of the fire. The fire-induced horizontal winds indicated the strongest fire-induced flow at the lowest measurement levels of the head fire (as high as 3.76 m/s) decreasing to 0.3 m/s at 20m above the ground. As a result, the most noticeable impacts of the fire-induced circulation on the fire rate of spread (ROS) were at the head fire. However, there were significant differences between the simulated and observed fire progression at the flanks. To examine to what degree, the observed discrepancies can be associated with the ROS algorithm used in the coupled fire-atmosphere model, two implementations of the Rothermel model as well as the Balbi model were examined. By running experiments in varying winds, fuel moisture and topography, we found the Balbi model is generally less sensitive to changes in the local conditions than the Rothermel model, providing a lower ROS. To investigate the features of the particular Rothermel model implementation in SFIRE, we compared it to the Behave model. We identified significant differences between the models which included different calculations within the model and different data which led to varying results between the two implementations of the same Rothermel model. The implementation of the Behave-based algorithm in WRF-SFIRE enabled using the 40 Scott and Burgan (S&B) fuel classifications not available before. Multiple simulations were run to analyze the behavior of the S&B fuels compared to the Albini fuels. Although many simulations produced similar burning characteristic, some S&B fuels burned differently than their equivalents in the Albini categories and resulted in a different atmospheric effects.

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