Vol. 11, no.1, 2019
РусскийEnglish
RADIOLOCATION
MICROWAVE SCATTERING IN DRY LAYERED SNOW
Valery A. Golunov
Kotelnikov Institute of Radioengineering and Electronics of RAS, Fryazino branch, http://fire.relarn.ru
Fryazino 141190, Moscow region, Russian Federation
Received 19.04.2019, accepted 24.04.2019
Abstract. The problem of the applicability of the two-stream Kubelka-Munk theory to the description of the radiative characteristics of snow cover is discussed. It is shown that since the microwave thermal radiation of snow is received by radiometers with a spatially coherent input, this is equivalent to the irradiation of scattering media by a spatially coherent and, as a rule, narrowly directed source, and the scattered radiation is received by an infinitely long areal receiver. The problem of the applicability of the known formulas for calculating the reflection and transmission coefficients of multilayer snow cover is considered, since the conditions for the applicability of these formulas and the Kubelka-Munk theory coincide. Moreover, the considered formulas do not take into account the reflection of flows at the boundaries between the layers. In the snow cover, the reflecting boundaries are caused by a jump in the refractive index due to the difference in the values of the bulk density of snow in adjacent layers. Measured at frequencies of 22.2, 31, 37.5 and 94 GHz, the values of the reflection and transmission coefficients of single-layer and multi-layer snow were compared with their calculated values. It is shown that, firstly, the measured dependences of the reflection and transmission coefficients on the thickness of single-layer snow are satisfactorily approximated by the corresponding formulas of the Kubelka-Munk theory. Secondly, the discrepancies between the calculated and measured values of the above factors for two-, three- and four-layer snow practically do not go beyond the limits of coarse measurement error. The experimentally observed negligibly small effect of the boundaries is interpreted by the fact that the calculations use the values of the reflection and transmission coefficients measured for each of the folded layers. These values already contain contributions from the reflections of scattered fluxes on the interlayer boundaries, of which the outer boundaries of the first and last layer are most important in the snow stack. The feasibility of creating a database of microwave radiation characteristics of a uniform (single-layer) dry snow cover with a wide set of parameters of its structure based on experimental data and a two-stream Kubelka-Munk model is shown. In this case, it becomes possible to simply and accurately predict the brightness characteristics of the layered snow cover.
Keywords: microwave emission, volume scattering, two-stream model, layered snow cover, experiment
UDC 535.36; 621.396.11
RENSIT, 2019, 11(1):39-48 DOI: 10.17725/rensit.2019.11.039
Full-text electronic version of this article - web site http://en.rensit.ru/vypuski/article/270/11(1)39-48e.pdf