Introduction

Biomass burning is a coupled exothermic/endothermic system that transfers carbon in several forms to the atmosphere, ultimately leaving mineral ash. The exothermic phases include flaming and smoldering, which produce the heat that drives the endothermic processes. The endothermic components include pre-heating and pyrolysis, which produce the fuel consumed by flaming and smoldering. These components can be broadly distinguished from each other based on temperature. For several years, we have researched the subpixel analysis of two temperature phases present in fire pixels detected in nighttime VIIRS data. Here, we present the flaming subtractive method, with which we have successfully derived temperatures and source areas for two infrared (IR) emitters and a cooler background. This is developed as an add-on to the existing VIIRS nightfire algorithm version 3 (VNF v.3) which uses Planck curve fitting to calculate temperatures and source areas for a single IR emitter and background. The flaming subtractive method works with data collected in four spectral ranges: near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR) and long-wave infrared (LWIR). With sunlight eliminated, the NIR and SWIR radiances can be fully attributed to the primary IR emitter. The analysis begins with Planck curve modeling for the primary emitter based on the NIR and SWIR radiances, yielding temperature, source area and primary emitter radiances in all spectral bands. The primary emitter radiances are subtracted from each spectral band and then the residual radiance is analyzed for a secondary IR emitter and the background. Spurious results are obtained in pixels lacking a discernable secondary emitter. These misfit pixels revert back to the single IR emitter analysis of VNF v.3. In tests run for two California megafires, we found that the primary emitters straddle the temperature ranges for flaming and smoldering, the exothermic portions of biomass burning, which are apparently commingled on the ground. The secondary emitter temperatures span 350–750 K, corresponding to pre-heating and slow pyrolysis. The natural gas flare test case had few numbers of successful secondary emitter retrievals and a wide range of secondary emitter temperatures. The flaming subtractive analysis is the key addition to VNF version 4, has commenced production the summer of 2023 and is now available for VNF licensees.

Improvements

• Introduces an atmospheric correction to account for atmospheric transmissivity differences.
• Instantaneous estimates of flared gas volume (introduced with VNF v3.5).
• Continues the dual curve Planck curve analysis (IR emitter and background) from VNF v.3 with atmospherically corrected radiances
• Adds a triple-phase analysis for pixels having SWIR and MWIR detection to derive primary and secondary emitters, plus background.
• VNF pixel labeling of multiyear IR emitter identification numbers.
• Improved the MWIR (M12-M13) detector to reduce false detections of combustion sources.
• Added an M14 long-wave infrared detector to provide further confirmation of secondary emitters.
• Utilizing M7 and M8 radiances in Planck curve fitting - even when detection is only in the SWIR.

Download

Readme (v40) is available HERE.  

VIIRS Nightfire algorithm had experience multiple upgrades. Currently we are archiving V2.1 derived from two sources, i.e. NOAA GRAVITE and NOAA CLASS. The operational one is V3.0.

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User with interim access can only download ezCSV. Only fully licensed users can access full CSV.

Credit

When using the data please credit the product generation to the Earth Observation Group, Payne Institute for Public Policy, with proper citations as below.

• Elvidge, Christopher D., Mikhail Zhizhin, Feng-Chi Hsu, Kimberly Baugh, M. Rokhis Khomarudin, Yenni Vetrita, Parwati Sofan, and Dadang Hilman. "Long-wave infrared identification of smoldering peat fires in Indonesia with nighttime Landsat data." Environmental Research Letters 10, no. 6 (2015): 065002.
• Elvidge, Christopher D., Mikhail Zhizhin, Feng-Chi Hsu, and Kimberly E. Baugh. “VIIRS nightfire: Satellite pyrometry at night.” Remote Sensing 5, no. 9 (2013): 4423-4449.
• Elvidge, Christopher D., Mikhail Zhizhin, Kimberly Baugh, and Feng-Chi Hsu. "Smoldering Peatland Fires in Indonesia via Triple-Phase Temperature Analysis of VIIRS Nighttime Data." Biomass Burning in South and Southeast Asia: Mapping and Monitoring, Volume One (2021): 25.
• Elvidge, Christopher D., Mikhail Zhizhin, Feng Chi Hsu, Tamara Sparks, and Tilottama Ghosh. "Subpixel Analysis of Primary and Secondary Infrared Emitters with Nighttime VIIRS Data." Fire 4, no. 4 (2021): 83.

Partners

OGCI: Oil and Gas Climate Initiative

NOAA: National Oceanic and Atmospheric Administration

SkyTruth

Satellite-Detected Natural Gas Flaring

The World Bank

Global Gas Flaring Reduction Partnership (GGFR)

Xprize Wildfire Competition