Approximation of the High-Temperature Fire Zone Based on Terra/MODIS Data in the Problem of Subpixel Analysis

In this work, an improved approach of the pixel-based analysis of the Terra/MODIS imagery is proposed. The approach allows us to improve the accuracy in estimating characteristics of the combustion zone when detecting thermal anomalies. The investigation is carried out based on the imagery of active vegetation fires in Siberian forests by the MODIS radiometer in the spectral ranges of 3930 to 3990 and 10 780 to 11 280 μm (bands 21 and 31, respectively). It is proposed to describe the approximation of the temperature profile of the fire front using an exponential function. Using the nonuniform approximation of the temperature distribution on the surface in the vicinity of the active combustion zone allows us to determine the portion of the active pixel of the Terra/MODIS image with the given temperature excess over the background temperature in it. This improves the accuracy in extracting active combustion zones and classifying the heat release rate at the subpixel level. This approach is applicable to monitoring fire development phases in the near real time mode.