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Donald W. Cline

Abstract

Snow surface energy exchanges and snowmelt were measured during the 1994 and 1995 snowmelt seasons at an alpine site in the Colorado Front Range (3517 m MSL, 40°03′N, 105°35′W). Following a maximum accumulation of 0.49-m snow water equivalence (SWE), the 1994 snowmelt season began on 5 May and lasted 32 days until 6 June. In contrast, the 1995 maximum accumulation of 1.31-m SWE did not occur until 1 June, and the snowmelt season lasted 45 days until July 16. Thus, a nearly threefold larger snowpack ablated in only 41% more time in the later 1995 snowmelt season. In 1994, net radiation accounted for 75% of the energy available to melt snow, and sensible and latent heat fluxes accounted for the remaining 25%. During the 1995 snowmelt season the mean air temperature was warmer (+1.3°C) and the mean specific humidity was greater (+0.6 g kg−1) than during the 1994 snowmelt season. As a result, in 1995, sensible and latent heat fluxes accounted for 54% of the energy for snowmelt and net radiation accounted for only 46%. Midday maximum snowmelt rates were approximately equal in 1994 and 1995; the overall more rapid 1995 melt rate was due to the frequent occurrence of nocturnal melting, which did not occur in 1994. The large differences between these two snowmelt seasons provide analogies for understanding regional variability of snowmelt processes and for understanding alpine snowmelt response to climate variability and change.

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Glen E. Liston, Christopher A. Hiemstra, Kelly Elder, and Donald W. Cline

Abstract

The Cold Land Processes Experiment (CLPX) had a goal of describing snow-related features over a wide range of spatial and temporal scales. This required linking disparate snow tools and datasets into one coherent, integrated package. Simulating realistic high-resolution snow distributions and features requires a snow-evolution modeling system (SnowModel) that can distribute meteorological forcings, simulate snowpack accumulation and ablation processes, and assimilate snow-related observations. A SnowModel was developed and used to simulate winter snow accumulation across three 30 km × 30 km domains, enveloping the CLPX mesocell study areas (MSAs) in Colorado. The three MSAs have distinct topography, vegetation, meteorological, and snow characteristics. Simulations were performed using a 30-m grid increment and spanned the snow accumulation season (1 October 2002–1 April 2003). Meteorological forcing was provided by 27 meteorological stations and 75 atmospheric analyses grid points, distributed using a meteorological model (MicroMet). The simulations included a data assimilation model (SnowAssim) that adjusted simulated snow water equivalent (SWE) toward ground-based and airborne SWE observations. The observations consisted of SWE over three 1 km × 1 km intensive study areas (ISAs) for each MSA and a collection of 117 airborne gamma observations, each integrating area 10 km long by 300 m wide. Simulated SWE distributions displayed considerably more spatial heterogeneity than the observations alone, and the simulated distribution patterns closely fit the current understanding of snow evolution processes and observed snow depths. This is the result of the MicroMet/SnowModel’s relatively finescale representations of orographic precipitation, elevation-dependant snowmelt, wind redistribution, and snow–vegetation interactions.

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Glen E. Liston, Daniel L. Birkenheuer, Christopher A. Hiemstra, Donald W. Cline, and Kelly Elder

Abstract

This paper describes the Local Analysis and Prediction System (LAPS) and the 20-km horizontal grid version of the Rapid Update Cycle (RUC20) atmospheric analyses datasets, which are available as part of the Cold Land Processes Field Experiment (CLPX) data archive. The LAPS dataset contains spatially and temporally continuous atmospheric and surface variables over Colorado, Wyoming, and parts of the surrounding states. The analysis used a 10-km horizontal grid with 21 vertical levels and an hourly temporal resolution. The LAPS archive includes forty-six 1D surface fields and nine 3D upper-air fields, spanning the period 1 September 2001 through 31 August 2003. The RUC20 dataset includes hourly 3D atmospheric analyses over the contiguous United States and parts of southern Canada and northern Mexico, with 50 vertical levels. The RUC20 archive contains forty-six 1D surface fields and fourteen 3D upper-air fields, spanning the period 1 October 2002 through 31 September 2003. The datasets are archived at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado.

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