Davos-Laret Remote Sensing Field Laboratory: 2016/2017 Winter Season L-Band Measurements Data-Processing and Analysis

Abstract

Abstract:The L-band radiometry data and in-situ ground and snow measurements performed during the 2016/2017 winter campaign at the Davos-Laret remote sensing field laboratory are presented and discussed. An improved version of the procedure for the computation of L-band brightness temperatures from ELBARA radiometer raw data is introduced. This procedure includes a thorough explanation of the calibration and filtering including a refined radio frequency interference (RFI) mitigation approach. This new mitigation approach not only performs better than conventional "normality" tests (kurtosis and skewness) but also allows for the quantification of measurement uncertainty introduced by non-thermal noise contributions. The brightness temperatures of natural snow covered areas and areas with a reflector beneath the snow are simulated for varying amounts of snow liquid water content distributed across the snow profile. Both measured and simulated brightness temperatures emanating from natural snow covered areas and areas with a reflector beneath the snow reveal noticeable sensitivity with respect to snow liquid water. This indicates the possibility of estimating snow liquid water using L-band radiometry. It is also shown that distinct daily increases in brightness temperatures measured over the areas with the reflector placed on the ground indicate the onset of the snow melting season, also known as "early-spring snow".

Snow Density and Ground Permittivity Retrieved from L-Band Radiometry: Melting Effects

“…While the present text provides extensive explanations regarding "LS-MEMLS", its general form, as well as its single dry-snow layer version, are comprehensively Remote Sens. 2018, 10, 354 6 of 26 explained in Section 5.1 in [41]. The reader is also referred to [30], in which both the specific single-layer dry-snow version of "LS-MEMLS" and the thereupon based retrieval of (ρ S , ε G ) are outlined.…”

“…A detailed explanation of the conversion of ELBARA-II raw data to calibrated brightness temperatures can be found in [41]. During the 2016/2017 winter campaign, L-band radiometry was performed over areas with a metal reflector placed on the ground.…”

“…This measurement cycle was performed once an hour throughout the campaign. Sky measurements, which as explained in Section 4.1 in [41], are necessary for the computation of calibrated brightness temperatures, were initiated manually during precipitation-free times, every other day when possible and done at nadir angle θ sky = 140 • .…”

“…Snow qualities, such as density, influence the energy budget through albedo feedbacks [17], and control thermal insulation of the soil [18], which in turn affects river run-off in the northern hemisphere [19][20][21] and mountainous [22] regions. Beyond the possibility of estimating snow liquid water using the sensitivity of L-band brightness temperatures to the snow moisture investigated in [41]. Therefore, the reader is strongly advised to consult the companion paper [40], which is closely linked to the analyses presented here.…”

“…A comprehensive description of the measurement campaign conducted at the Davos-Laret Remote Sensing Field Laboratory (Switzerland), the processing of the calibrated L-band brightness temperatures, and the in-situ reference data are outlined in detail in [41]. Section 2 provides selected information on the measurement configuration, and the in-situ and radiometry data collection that is necessary for this study.…”