The inhomogeneity of the atmosphere causes curvature (refraction) of the beam path of ultra-short radio waves. Under normal conditions, this trajectory curves towards the surface of the Earth, and its curvature is about one quarter of the curvature of the earth's surface. Under critical conditions, the appearance of the phenomenon of "superrefraction" is possible. A feature of ultra-short radio waves is the fact that meteorological conditions influence their propagation. Measurements of meteorological parameters at h1 = 2 and h2 = 10 meters were carried out using an atmospheric-soil measuring complex installed in the southwestern part of the Vitim Plateau. It has been established that in this layer the spread of refractivity gradient values is from –0.820 to +0.307 N-units. It was found that meteorological conditions favorable for the appearance of superrefraction are observed in the given area in the summer.
The dynamics of the atmosphere has a significant impact on the propagation of ultrashort radio waves. The atmospheric refraction index is the main radio meteorological characteristic of ultrashort waves. Calculations and construction of contours of the refractive index N in the atmosphere of the Republic of Buryatia and the Irkutsk region were carried out. The contours of average N for the study area for January and July 2020 are presented.
Vegetation maps play a key role in an estimation of forest fire danger. To estimate forest fire danger, a vegetation type map of Gilbirinsky forestry situated in the Lake Baikal basin was created on basis of both the remote sensing data and field study. A Sentinel-2A satellite image was classified by the maximum likelihood method. Zones with different levels of forest fire danger have been identified: coniferous forests–extremely dangerous level, mixed forests – high level, and deciduous forests–moderate level of forest fire danger. Normalized Difference Water Index has been calculated and moisture content in vegetation has been evaluated.
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