Lighting the dark: Insights of nighttime fire emissions from space

Abstract:

The first detection of fires from space was made available in early 1970s by using visible light intensity measured at nightby Sensor Aerospace Vehicle Electronics Package (SAP) as part of the Defense Meteorological Satellite Program (DMSP). Unrelated to the DMSP, the TIROS-N satellite was launched in 1978 by NOAA, which carried a powerful instrument for its time: the Advanced Very High Resolution Radiometer (AVHRR). It was subsequently shown that the AVHRR’s mid-wave infrared (MWIR) channel is sensitive to hot sources such as steel mills in Ohio River Valley and gas flares in the Middle East. Since then, the fire detection algorithms have evolved from AVHRR into the realm of more sophisticated sensors and to geostationary satellites, but they are still based on that principle: the enhancement in radiance/brightness temperature (BT) between MWIR, thermal infrared (TIR), and to some degree near infrared (NIR) wavelengths from fires. While significant progresses have been made in using infrared channels for active fire detection in the past 4 decades, the launch of Suomi-NPP satellite in 2012 opened a new era to quantitively use visible images at night to characterize fires and renew the legacy of first fire detection from space made possible by DMSP early 1970s.

In this presentation, I will highlight the progress and insights we’ve made of using the Day-Night-Band (DNB) of Visible Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP to improve fire detection and characterize fire combustion efficiency at night. A hybrid usage of VIIRS DNB and infrared band to quantify the visible energy fraction (VEF) as an indicator of fire burning phase will be presented. VEF is calculated as the ratio of visible light power (VLP) and FRP for each fire pixel retrieved from VIIRS 750 m active fire product. A global distribution of VEF values, and thereby the fire phase, is quantitatively obtained, showing mostly smoldering wildfires such as peatland fires (with smaller VEF values) in Indonesia, flaming wildfires (with larger VEF values) over grasslands and savannahs in sub-Sahel region, and gas fares with largest VEF values in the Middle East. The advantages of using VEF will also be illustrated to describe the life cycle of Camp fire in 2018 – the most devasting fire in the history of California. Finally, a discussion of validating VEF and using VEF to improve fire emission estimated are provided.