Remote Sensing, Model-Derived and Ground Measurements of Snow Water Equivalent and Snow Density in Alaska

Reginald R Muskett

doi:10.4236/ijg.2012.35114

Abstract

Snow water equivalent (SWE) is important for investigations of annual to decadal-scale changes in Arctic environment and energy-water cycles. Passive microwave satellite-based retrieval algorithm estimates of SWE now span more than three decades. SWE retrievals by the Advanced Microwave Scanning Radiometer for the Earth Observation System (AMSR-E) onboard the NASA-Aqua satellite ended at October 2011. A critical parameter in the AMSR-E retrieval algorithm is snow density assumed from surveys in Canada and Russia from 1940s-1990s. We compare ground SWE measurements in Alaska to those of AMSR-E, European Space Agency GlobSnow, and GIPL model. AMSR-E SWE underperforms (is less than on average) ground SWE measurements in Alaska through 2011. Snow density measurements along the Alaska permafrost transect in April 2009 and 2010 show a significant latitude-gradient in snow density increasing to the Arctic coast at Prudhoe Bay. Large differences are apparent in comparisons of our measured mean snow densities on a same snow cover class basis March-April 2009-2011 Alaska to those measured in Alaska winter 1989-1992 and Canadian March-April 1961-1990. Snow density like other properties of snow is an indicator of climate and a non-stationary variable of SWE.

Highlights

Snow water equivalent (SWE), the equivalent amount of water of a snow on the ground is a fundamental parameter of climate, environment and energy-water cycles on Earth
SWE is the uniform thickness of water melted from snow in length units of meters (m), snow depth multiplied by snow density is divided by pure-water density) or in mass/volume units of kilograms/meter-cubed, snow depth multiplied by snow density)
Regressions (Table 3) show that both GlobSnow and AMSR-E increase, as do the ground measurements following the days of snowfall events

Summary

Introduction

Snow water equivalent (SWE), the equivalent amount of water of a snow on the ground is a fundamental parameter of climate, environment and energy-water cycles on Earth. SWE is the uniform thickness of water melted from snow in length units of meters (m), snow depth multiplied by snow density is divided by pure-water density) or in mass/volume units of kilograms/meter-cubed (kg/m2), snow depth multiplied by snow density). In this report we use the length scale centimeter for SWE and the mass/volume scale g/cm for snow density. I.e. bulk snow density, (Table 1) is influenced by temperature changes, grain size and microstructure, granular humidity and surface wind after deposition [2]. This dependence is due to the low pressuretemperature triple-point thermodynamics of ice [3]. Due to compaction and metamorphic processes within snowpack, snow density changes during the winter season

Results

Discussion

Conclusion