Estimation of Byram’s Fire Intensity and Rate of Spread from Spaceborne Remote Sensing Data in a Savanna Landscape

Gernot Ruecker,David Leimbach,Joachim Tiemann

doi:10.3390/fire4040065

Abstract

Fire behavior is well described by a fire’s direction, rate of spread, and its energy release rate. Fire intensity as defined by Byram (1959) is the most commonly used term describing fire behavior in the wildfire community. It is, however, difficult to observe from space. Here, we assess fire spread and fire radiative power using infrared sensors with different spatial, spectral and temporal resolutions. The sensors used offer either high spatial resolution (Sentinel-2) for fire detection, but a low temporal resolution, moderate spatial resolution and daily observations (VIIRS), and high temporal resolution with low spatial resolution and fire radiative power retrievals (Meteosat SEVIRI). We extracted fire fronts from Sentinel-2 (using the shortwave infrared bands) and use the available fire products for S-NPP VIIRS and Meteosat SEVIRI. Rate of spread was analyzed by measuring the displacement of fire fronts between the mid-morning Sentinel-2 overpasses and the early afternoon VIIRS overpasses. We retrieved FRP from 15-min Meteosat SEVIRI observations and estimated total fire radiative energy release over the observed fire fronts. This was then converted to total fuel consumption, and, by making use of Sentinel-2-derived burned area, to fuel consumption per unit area. Using rate of spread and fuel consumption per unit area, Byram’s fire intensity could be derived. We tested this approach on a small number of fires in a frequently burning West African savanna landscape. Comparison to field experiments in the area showed similar numbers between field observations and remote-sensing-derived estimates. To the authors’ knowledge, this is the first direct estimate of Byram’s fire intensity from spaceborne remote sensing data. Shortcomings of the presented approach, foundations of an error budget, and potential further development, also considering upcoming sensor systems, are discussed.

Highlights

Implementing the tests outlined in the methods section greatly reduced the number of fire front pairs available for analysis, and it was necessary to relax the criteria for exclusion of already-burned areas
For a first quantitative analysis of fire intensity and rate of spread, fire clusters were visually screened, and analysis limited to samples which were considered to be most likely associated to a common ignition and the associated connection between the fronts through spread vectors were considered likely to be correct
We have developed and tested a method to directly estimate rate of spread and Byram’s fire or fireline intensity from satellite remote sensing observations using high

Summary

Introduction

Often fire behavior is described by a fire’s rate of spread and its energy release rate. These are combined into fire intensity or fireline intensity as defined by Byram, which is the most commonly used single parameter describing fire behavior in the wildfire community [1,2,3]. Describing fire behavior is important to estimate a fire’s ecological impact as well as to decide upon an adequate management response and, in the case a fire is to be suppressed, to ensure the safety of fire-fighting operations (see, e.g., [4]). Fireline intensity is widely used in savanna fire ecology [1,5,6], and it has been hypothesized that shifting African fire regimes to early season burns—

Methods

Results

Conclusion