Comparison of VIIRS and MODIS active fire products over South Sumatra

Abstract

This study aims to compare VIIRS and MODIS active fire data (hotspots) over a humid tropical region in Southeast Asia. Both VIIRS and MODIS employ similar algorithms for active fire detection but VIIRS hotspots have a nominal resolution of 375 m, in comparison to 1 km for MODIS. Thus, VIIRS is expected to have greater response for smaller fires as well as improved mapping of large fires. Daily VIIRS and MODIS active fire products from 2012 to 2017 were downloaded from NASA FIRMS web site. Only data from afternoon passes over South Sumatra, Indonesia were used in this study. Overall, for the whole 6 year period, 52.0ȥ of Aqua-MODIS hotspots were in agreement with VIIRS while only 22.7% of VIIRS hotspots agreed with Aqua-MODIS. However, on further analysis, the apparently low agreement was probably due to false alarms during off-fire seasons. The average false alarm rate during off-fire seasons was about 1 per day for MODIS. For 10 days in September 2015 when severe vegetation fires occurred, 73.2ȥ of Aqua-MODIS hotspots agreed with VIIRS while 47.1% of VIIRS hotspots agreed with Aqua-MODIS. For large fires visible in 500-m resolution VIIRS false color images, the detection rate by VIIRS was 97.4% and 83.3% by MODIS. VIIRS might also detect smaller and/or less intense fires that were not detectable by Aqua-MODIS.