Snow Wetness Reftrieved from L-Band Radiometry

The present study demonstrates the successful use of L-band brightness temperatures T
_B
^p
to retrieve snow liquid water W
_s
from multi-angular measurements T
_B
^p
(θ
_k
). The emission model employed was developed from parts of the “microwave emission model of layered snowpacks” (MEMLS) coupled with components adopted from the “L-band microwave emission of the biosphere” (L-MEB) model. Two types of snow liquid water retrievals were performed based on T
_B
^p
(θ
_k
) measured over i) areas with a metal reflector placed on the ground (“reflector area”-T
^p
_B,R
), and ii) natural snow-covered ground (“natural area”-T
^p
_B,N
). The reliable representation of temporal variations of snow liquid water is demonstrated for both types of retrievals. This is verified by the fact that both types of W
_s
-retrievals indicate a dry snowpack throughout the “cold winter period” with frozen ground and air temperatures well below freezing, and synchronously respond to snowpack moisture variations during the “early spring period”. Snow liquid water retrievals based on T
^p
_B,N
are achieved in a two-step retrieval procedure using exclusively L-band brightness temperatures, without the need for in-situ measurements such as ground permittivity CG and snow mass-density ρs. The latter two are estimated in the first retrieval-step employing the well-established two-parameter (ρs, ε
_G
) retrieval scheme. The proposed and investigated two-step retrieval approach opens up the possibility of using airborne or spaceborne L-band radiometry to estimate (ρ
_s
, ε
_G
, W
_s
).