Global Analysis of Burned Area Persistence Time with MODIS Data

Andrea Melchiorre,Luigi Boschetti

doi:10.3390/rs10050750

Abstract

Biomass burning causes a non-permanent land cover change (burned area) through the removal of vegetation, the deposition of charcoal and ashes, and the exposure of soil; the temporal persistence of these changes is highly variable, ranging from a few weeks in savannas to years in forests. Algorithms for the generation of moderate-resolution (10–30 m) continental and global burned area maps have been prototyped in an effort to meet the needs of diverse users of fire information. Nevertheless, moderate-resolution sensors have reduced the temporal resolution (e.g., to 16 days for Landsat), which could potentially lead to omission errors, especially in ecosystems where the spectral signal associated with burning disappears quickly and cloud cover limits the number of valid observations. This study presents a global analysis of the burned area persistence time, defined as the duration of the spectral separability of the burned/unburned areas mapped by the MODIS MCD64 Global Burned Area Product. The separability was computed by analyzing time series of normalized burn ratio (NBR) from nadir BRDF-adjusted MODIS reflectances (MCD43 product). Results showed that, globally, the median burned area persistence time was estimated at 29 days, and 86.6% of the global area, as detected by MODIS, can only be detected accurately for up to 48 days. Thus, results indicate that burned area persistence time can be a limiting factor for global burned area mapping from moderate-resolution satellite sensors, which have a low temporal resolution (e.g., Landsat 16 days, Sentinel-2A/B 5 days).

Highlights

Fire is a natural component of any ecosystem, and it has effects on vegetation, soil, water and atmospheric composition [1,2,3]
From 2003 to 2016, the MODIS MCD64A1 product detected, on average, 4.0 × 106 km2 of burned area per year: 0.19 × 106 km2 in Forest, 0.31 × 106 km2 in Shrubland, 3.1 × 106 km2 in Grassland & Savanna, and the remaining 0.40 × 106 km2 occurring in croplands and other land covers not considered in this study
Out of the 867 ecoregions defined by the TEOW map, 511 ecoregions had more than 250 km2 of burned area detected in at least one land cover class over the study period, and were considered in the analysis (Section 3.2.1); 300 ecoregions were considered for the Forest land cover class, 135 for Shrubland and 392 for Grassland & Savanna (Figure 7, right column)

Summary

Introduction

Fire is a natural component of any ecosystem, and it has effects on vegetation, soil, water and atmospheric composition [1,2,3]. The application of satellite data to studying vegetation fires has greatly enhanced the possibility of introducing the effect of fire disturbances in global models of climate and atmospheric composition and dynamics estimation [12]. Several studies have used post-fire albedo observations to investigate fire-induced vegetation change impacts on radiative forcing and local effects on climate [9,13,14]. Due to their significant effects on terrestrial ecosystems and atmospheric processes, fire disturbances are included in the list of the required Essential Climate Variables (ECV) in support of the work of the United Nation Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) [15]

Methods

Results

Discussion

Conclusion