Abstract
Snow depth and snow water equivalent (SWE) are two parameters for measuring snowfall. By exploiting the Global Navigation Satellite System reflectometry (GNSS-R) technique and thousands of existing GNSS Continuous Operating Reference Stations (CORS) deployed in the cryosphere, it is possible to improve the temporal and spatial resolutions of the SWE measurement. In this paper, a fusion model for combining multi-satellite SNR (Signal to Noise Ratio) snow depth estimations is proposed, which uses peak spectral powers associated with each of the snow depth estimations. To simplify the estimation of SWE, the complete snowfall period over a winter season is split into snow accumulation, transition, and melting period in accordance with the variation characteristics of snow depth and SWE. By extensively using in situ snow depth and SWE observations recorded by snow telemetry network (SNOTEL) and regression analysis, three empirical models are developed to describe the relationship between snow depth and SWE for the three periods, respectively. Based on the snow depth fusion model and the SWE empirical models, an SWE estimation algorithm is proposed. Three data sets recorded in different environments are used to test the proposed method. The results demonstrate that there exists good agreement between the in situ SWE measurements and the SWE estimates produced by the proposed method; the root-mean-square error of SWE estimations is smaller than 6 cm when the SWE is up to 80 cm.
Highlights
The snow water equivalent (SWE) describes the amount of liquid water in the snowpack, which is the depth of water if the snow cover over the ground becomes liquid
According to the snow depth records over the years in the area, the snow depth hit its maximum in February
Note that the SNR-based snow depth estimations, produced by two different average techniques, are presented in the figure; NA refers to the results obtained by the normal average and WA refers to the results obtained by the weighted average, which is obtained by Equation (7)
Summary
The snow water equivalent (SWE) describes the amount of liquid water in the snowpack, which is the depth of water if the snow cover over the ground becomes liquid. Global Navigation Satellite System reflectometry (GNSS-R) makes use of the GNSS signals to remotely monitor the characteristics of the object surface which reflects the signals. This technique has been investigated for the measurement of a range of geophysical parameters, including ocean surface height and wind speed, soil moisture, vegetation, snow depth and SWE [2,3,4,5]. By making use of the GNSS-R technique, these stations located in cold regions could provide a cost-effective way for SWE monitoring
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