Detection of the Depth-Hoar Layer in the Snow-Pack of the Arctic Coastal Plain of Alaska, U.S.A., Using Satellite Data

Abstract

(Hydrological Sciences Bra nch , NASA /G oddard Space Flight Cente r , Gree nbe lt , M a ryl and 20771, U .S .A .)ABSTRACT. The snow-pack on the Arctic Coastal Plain of Alaska has a well-developed depth-hoar layer which forms each year at the base of the snow-pack due to upward vapor transfer resulting from a temperature gradient in the snow-pack. The thickness of the depth-hoar layer tends to increase inland where greater temperature extremes (in particular, lower minimum temperatures) permit larger temperature gradients to develop within the snow-pack . Brightness temperature (TB) data were analyzed from October through May for four winters using the 37 GHz horizontally polarized Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR). By mid-winter each year, a decrease in TB of approximately 20K was found between coastal and inland sites on the Arctic Coastal Plain of Alaska. Modeling has indicated that a thicker depth-hoar layer in the inland sites could be responsible for the lower T BS ' The large grain-sizes of the depth-hoar crystals scatter the up welling radiation moreso than do smaller crystals, and greater scattering lowers the microwave TB' Using a two-layered radiative transfer model, the crystal diameter in the top layer was assumed to be 0.50 mm. The crystals in the depth-hoar layer may be 5-10 mm in diameter but the effective crystal diameter used in the radiative-transfer model is 1.40 mm. The crystal size used in the model had to be adjusted downward, relative to the actual crystal size, because the hollow, cup-shaped depth-hoar crystals are not as effective at scattering the microwave radiation as are spherical crystals that are assumed in the model. In the model, when the thickness of the depth-hoar layer was increased from 5 cm to 10 cm, a 21K decrease in TB resulted. This is comparable to the decrease in TB observed from coastal to inland sites in the study area.

Comparison of passive microwave brightness temperature prediction sensitivities over snow-covered land in North America using machine learning algorithms and the Advanced Microwave Scanning Radiometer

“…These satellite-based SWE retrieval models are often affected by errors arising from meteorological fields (e.g., data aggregation, disaggregation, extrapolation and interpolation (Blöschl & Sivapalan, 1995)) used to force land surface models. They are also affected by significant uncertainties associated with snow stratigraphy (Derksen, Walker, & Goodison, 2005), snow grain size (Armstrong, Chang, Rango, & Josberger, 1993), depth hoar layer (Brucker, Royer, Picard, Langlois, & Fily, 2011;Hall, 1987;Hall, Chang, & Foster, 1986;Foster et al, 2005), ice crusts (Rees, Lemmetyinen, Derksen, Pulliainen, & English, 2010), lake fraction effects , and snow morphology (Kelly et al, 2003), especially in densely-vegetated regions (Tedesco & Narvekar, 2010;Derksen et al, 2005) with relatively deep snow (Clifford, 2010). Remote Sensing of Environment 170 (2015) [153][154][155][156][157][158][159][160][161][162][163][164][165] In an effort to overcome many of the limitations highlighted above, the third alternative involves merging measurements of remote sensing observations with estimates from physically-based models (Reichle, 2008;Forman, Reichle, & Rodell, 2012;Reichle, De Lannoy, Forman, Draper, & Liu, 2014) using data assimilation (DA).…”

Spatiotemporal Characteristics of Snowpack Density in the Mountainous Regions of the Western United States

“…Constructive metamorphism produces large and complex-shaped grains called depth hoar. This metamorphism process happens particularly in cold regions such as Alaska (Hall et al 1986) and in the interior of the western United States such as Wyoming during early winter (Josberger et al 1996). A snowpack dominated by depth hoar undergoes slower densification than finer grain snowpack because large and complex-shaped snow grains experience minimal sintering (Colbeck 1997).…”

Large-Scale High-Resolution Modeling of Microwave Radiance of a Deep Maritime Alpine Snowpack

“…Indeed, increases in T b in response to the snowfall were observed in the AMSR-E data in this paper and were reproduced by the model (see Figs. 3 attributable to the differences in the density, the grain size, and the stratigraphy of the snowpack [7], [52], [54].…”