A Decade Long, Multi-Scale Map Comparison of Fire Regime Parameters Derived from Three Publically Available Satellite-Based Fire Products: A Case Study in the Central African Republic

Patrick Freeborn,Martin Wooster,Mark Cochrane

doi:10.3390/rs6054061

Abstract

Although it is assumed that satellite-derived descriptions of fire activity will differ depending on the dataset selected for analysis, as of yet, the effects of failed and false detections at the pixel level and on an instantaneous basis have not been propagated through space and time to determine their cumulative impact on the characterization of individual fire regime parameters. Here we perform the first ever decade long, multi-scale map comparison of fire chronologies and fire seasonality derived from three publicly available satellite-based fire products: the MODIS active fire product (MCD14ML), the ATSR nighttime World Fire Atlas (WFA), and the MODIS burned area product (MCD45A1). Results indicate that: (i) the agreement between fire chronologies derived from two dissimilar satellite products improves as fire pixels are aggregated into coarser grid cells, but diminishes as the number of years included in the time series increases; and (ii) all three datasets provide distinctly different portraits of the onset, peak, and duration of the fire season regardless of the map resolution. Differences in regional, long-term fire regime parameters derived from the three datasets are attributed to the unique capability of each sensor and detection algorithm to recognize geographical gradients, seasonal oscillations, decadal trends, and interannual variability in active fire characteristics and burned area patterns. Since different satellite sensors and detection algorithm strategies are sensitive to different types of fires, we demonstrate that disagreements in fire regime maps derived from dissimilar satellite-based fire products can be used as an advantage to highlight spatial and temporal transitions in landscape fire activity. Given access to multiple, publically available datasets, we caution against describing fire regimes using a single satellite-based active fire or burned area product.

Highlights

Mapping fire regimes is useful for understanding disturbance-vegetation-climate interactions, for assessing ecological integrity and ecosystem change, for identifying fire hazard and fire risk, for informing fire, fuels and resource management decisions, and for identifying gaps in knowledge about the spatiotemporal patterns of fire [1,2,3]
Binary maps of annual fire occurrence in the Central African Republic (CAR) derived from the MODIS (MCD14ML) and (A)Along Track Scanning Radiometer (ATSR) (WFA) active fire datasets showed poor agreement in 2002 & 2003 at the finest spatial resolution
Less than 1% of the 0.05° grid cells in the CAR contained at least one (A)ATSR active fire pixel detected during the year but no MODIS AF

Summary

Introduction

Mapping fire regimes is useful for understanding disturbance-vegetation-climate interactions, for assessing ecological integrity and ecosystem change, for identifying fire hazard and fire risk, for informing fire, fuels and resource management decisions, and for identifying gaps in knowledge about the spatiotemporal patterns of fire [1,2,3]. Given the time, cost, and limited coverage of field surveys, and the geostatistical issues associated with extrapolating spatial data [1,13], satellite images of active fires and burned areas are increasingly being used to monitor fire histories as they unfold [14]. Active fire detection strategies rely on increased infrared brightness temperatures to identify sub-pixel hotspots burning at the time of image acquisition [15,16], and burned area detection strategies identify changes in the pre- and post-fire surface reflectance that accompanies fuel consumption, the deposition of char and ash, and the alteration of vegetative cover [17]. Information about the timing and location of active fire (AF) and burned area (BA) pixels is stored in data files often referred to as “fire products.”. The accumulation of multiple AF and BA pixels represents multiple observations of the same fire through time and across the landscape

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Discussion

Conclusion