Preprints
https://doi.org/10.5194/gmd-2021-334
https://doi.org/10.5194/gmd-2021-334

Submitted as: development and technical paper 03 Nov 2021

Submitted as: development and technical paper | 03 Nov 2021

Review status: this preprint is currently under review for the journal GMD.

Representing Low-Intensity Fire Sensible Heat Output in a Mesoscale Atmospheric Model with a Canopy Submodel: A Case Study with ARPS-CANOPY (version 5.2.12)

Michael T. Kiefer1, Warren E. Heilman2, Shiyuan Zhong1, Joseph J. Charney2, Xindi Bian2, Nicholas S. Skowronski3, Kenneth L. Clark4, Michael R. Gallagher4, John L. Hom2, and Matthew Patterson3 Michael T. Kiefer et al.
  • 1Department of Geography, Environment, and Spatial Sciences, Michigan State University, East Lansing, MI 48824, USA
  • 2USDA Forest Service, Northern Research Station, Lansing, MI 48910, USA
  • 3USDA Forest Service, Northern Research Station, Morgantown, WV 26505, USA
  • 4USDA Forest Service, Northern Research Station, New Lisbon, NJ 08064, USA

Abstract. Mesoscale models are a class of atmospheric numerical model designed to simulate atmospheric phenomena with horizontal scales of about 2–200 km, although they are also applied to microscale phenomena, with horizontal scales less than about 2 km. Mesoscale models are capable of simulating wildland fire impacts on atmospheric flows if combustion by-products (e.g., heat, smoke) are properly represented in the model. One of the primary challenges encountered in applying a mesoscale model to studies of fire-perturbed flows is the representation of the fire sensible heat source in the model. Two primary methods have been implemented previously: turbulent sensible heat flux, either in the form of an exponentially-decaying vertical heat flux profile or surface heat flux; and soil temperature perturbation. In this study, the ARPS-CANOPY model, a version of the Advanced Regional Prediction System (ARPS) model with a canopy submodel, is utilized to simulate the turbulent atmosphere during a low-intensity operational prescribed fire in the New Jersey Pine Barrens. The study takes place in two phases: model assessment and model sensitivity. In the model assessment phase, analysis is limited to a single control simulation in which the fire sensible heat source is represented as an exponentially-decaying vertical profile of turbulent sensible heat flux. In the model sensitivity phase, a series of simulations are conducted to explore the sensitivity of model-observation agreement to (i) the method used to represent the fire sensible heat source in the model and (ii) parameters controlling the magnitude and vertical distribution of the sensible heat source. In both phases, momentum and scalar fields are compared between the model simulations and data obtained from six flux towers located within and adjacent to the burn unit. The multi-dimensional model assessment confirms that the model reproduces the background and fire-perturbed atmosphere as depicted by the tower observations, although the model underestimates the turbulent kinetic energy at the top of the canopy at several towers. The model sensitivity tests reveal that the best agreement with observations occurs when the fire sensible heat source is represented as a turbulent sensible heat flux profile, with surface heat flux magnitude corresponding to the peak 1-min mean observed heat flux averaged across the flux towers, and an e-folding extinction depth corresponding to the average canopy height in the burn unit. The study findings provide useful guidance for improving the representation of the sensible heat released from low-intensity prescribed fires in mesoscale models.

Michael T. Kiefer et al.

Status: open (until 29 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-334', Anonymous Referee #1, 21 Nov 2021 reply

Michael T. Kiefer et al.

Data sets

Representing Low-Intensity Fire Sensible Heat Output in a Mesoscale Atmospheric Model with a Canopy Submodel: A Case Study with ARPS-CANOPY (version 5.2.12) [Data set] Kiefer, M. T., Heilman, W. E., Zhong, S., Charney, J. J., Bian, X., Skowronski, N. S., Clark, K. L., Gallagher, M. R., Hom, J. L., and Patterson, M. https://doi.org/10.7910/DVN/JJCPND

Michael T. Kiefer et al.

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Short summary
We examine methods used to represent wildland fire sensible heat release in atmospheric models. A set of simulations are evaluated using observations from a low-intensity prescribed fire in the New Jersey Pine Barrens. The comparison is motivated by the need for guidance regarding the representation of low-intensity fire sensible heating in atmospheric models. Such fires are prevalent during prescribed fire operations and can impact the health and safety of fire personnel and the public.