Measuring snow liquid water content with low-cost GPS receivers.

Franziska Koch,Wolfram Mauser,Monika Prasch,Jürg Schweizer,Lino Schmid

doi:10.3390/s141120975

Abstract

The amount of liquid water in snow characterizes the wetness of a snowpack. Its temporal evolution plays an important role for wet-snow avalanche prediction, as well as the onset of meltwater release and water availability estimations within a river basin. However, it is still a challenge and a not yet satisfyingly solved issue to measure the liquid water content (LWC) in snow with conventional in situ and remote sensing techniques. We propose a new approach based on the attenuation of microwave radiation in the L-band emitted by the satellites of the Global Positioning System (GPS). For this purpose, we performed a continuous low-cost GPS measurement experiment at the Weissfluhjoch test site in Switzerland, during the snow melt period in 2013. As a measure of signal strength, we analyzed the carrier-to-noise power density ratio (C/N0) and developed a procedure to normalize these data. The bulk volumetric LWC was determined based on assumptions for attenuation, reflection and refraction of radiation in wet snow. The onset of melt, as well as daily melt-freeze cycles were clearly detected. The temporal evolution of the LWC was closely related to the meteorological and snow-hydrological data. Due to its non-destructive setup, its cost-efficiency and global availability, this approach has the potential to be implemented in distributed sensor networks for avalanche prediction or basin-wide melt onset measurements.

Highlights

Seasonal snow is a very important reservoir component in the hydrological cycle, which releases temporarily delayed fresh water to the forelands
The liquid water content (LWC) of the snowpack covering the antennas GPS2 and GPS3 at the Weissfluhjoch test site was calculated for the three-months spring period (7 April–6 July 2013) in half-hourly temporal resolution
We showed that the bulk volumetric LWC derived from Global Positioning System (GPS) data was highly sensitive to the daily meteorological and snow-hydrological evolution and can plausibly be explained by them

Summary

Introduction

Seasonal snow is a very important reservoir component in the hydrological cycle, which releases temporarily delayed fresh water to the forelands. Describes the total amount of snow stored within a certain catchment. This measure does not provide information on the state of snow melting. The liquid water content (LWC) θw in snow describes the snow wetness of a snowpack. It is an indicator for snow melt and snow stability. A clear increase in liquid water leads to an onset of meltwater runoff within a catchment. This is relevant information, e.g., for flood predictions during intense melting due to intense solar radiation or rain-on-snow events

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