Simulating VIIRS Observed Gas Flare

Abstract:

VIIRS Nightfire (VNF) had been proved being able to effectively detect gas flares at night, and characterize their temperature and source size. [1] However, limited access to generally confidential gas flare operation measurements made it difficult to verify the output. Although flared gas volume is occasionally available, it is not common to log the temperature and flames size which directly links to VNF output.
To understand the mechanism of gas flare and how VIIRS perceives the event, a platform is proposed to simulate the gas flare being observed by VIIRS. The methodology can be described in three steps. (1) Use CFD simulation software ISIS-3D to simulate a simple gas flare. [2] Scalar fields of temperature and species concentration related to combustion are extracted from the simulation. The instantaneous scalar can be determined from time-averaging or guess by stochastic time and space series (TASS) from single-point statistics [3]. (2) Model spectral radiance intensity of simulated gas flare using RADCAL. [4] RADCAL developed by NIST can accurately model the spectral radiance emitted on the direction of lineof-sight given the spatial profile of temperature and concentration of species. (3) Use radiative transfer modeling to calculate the energy propagated to VIIRS. The modeled radiation will then be weighted by the MODTRAN [5] modeled transmissivity over predefined atmosphere to the satellite, with geometrical effects considered.
Such platform can help understanding how exactly VNF is measuring gas flares, and thus lead to more precise characterization of combustion events.

[1] C. D. Elvidge et al, Remote Sensing, 2013
[2] IRSN ISIS-3D
[3] M. E. Kounalakis et al, ASME J. Heat Transfer, 1991
[4] W. L. Grosshandler, NIST Technical Note 1402, 1993
[5] A. Berk et al, MODTRAN 5.2.0.0 User’s Manual