Variability of Fire Radiative Power under the Conditions of Burning in Larch Forests of Siberia

The variability of heat emission from fires in Siberian larch stands (within the boundaries of 60°–65° N, 100°–130° E) was studied. We used the sample of the seven largest wildfires with a total area of 10 000 km² recorded in 2018, 2020, and 2021. For comparison, we analyzed a selection of wildfires recorded in 2015–2021 (29 fires, on a total area of up to 18 000 km²) with reference to other predominant variants of vegetation in Siberia: spars larch, stands of pine, spruce, Siberian pine (cedar), as well as tundra vegetation and Siberian dwarf pine (Pinus pumila). We operated with the data on radiation power from active combustion zones, calculated using the fire radiative power (FRP) method and standard MODIS products. It is pointed out that the relative burn area of larch stands (γ = 0.69%) exceeds by at least 2 times the same characteristic of other variants of vegetation in Siberia. It is shown that quasi-normal distribution of FRP values is typical for all large-scale fires (with area \( \gg \) 20 km²) of Siberia, including fires in larch forests. FRP from fires in larch forests can range from 12 000 to >260 000 MW. At the same time, the sporadic extremes of integral FRP (FRP_int) are an order of magnitude higher than the values corresponding to other variants of vegetation. The average FRP per a pixel of MODIS for fires in larch forests are 15% higher than the ones for pine stands and 25–35% higher than the typical values for fires in dark coniferous forests. The relation of FRP_int with the area of active combustion is approximated by a linear function with a confidence of at least 0.6 (p < 0.05). At the same time, the value of FRP_int aggregated over the entire period of fire development depends logarithmically on the final burned area. Based on the dependence, it is possible to estimate the characteristic realization time of the three phases of wildfire dynamics not only in terms of burned area, but also using energy characteristics in terms of heat emission.