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Mark T. Stoelinga, Mark D. Albright, and Clifford F. Mass

1. Introduction The multidecadal variation of snowpack in the Cascade Mountains of the Pacific Northwest is an issue of substantial scientific interest, societal impact, and some controversy. Major scientific issues include determining the magnitude of recent snowpack changes, the dependence of snowpack trends on the period examined, and the importance of natural climate variability versus anthropogenic global warming on past and future snowpack changes. The societal and ecological impacts of

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Amato T. Evan

1. Introduction In the western United States, the majority of precipitation falls during the wintertime ( Mock 1996 ), and consequently water supply is heavily dependent upon the amount of precipitation that is stored in mountain snowpack, specifically because snowmelt provides a steady and gradual source of water runoff ( Doesken and Judson 1996 ). As such, year-to-year changes in snow accumulation and melt can have major impacts on water management since the timing of the availability of

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M. J. Tribbeck, R. J. Gurney, and E. M. Morris

simple enough to apply over different areas without the need for extensive field measurements to initialize the model. The interaction of radiation between the snowpack and forest canopy is simulated by coupled physically based snow and canopy models. The snow component model is a multilayer one-dimensional model based on SNTHERM ( Jordan 1991 ). The canopy component determines the scattering and absorption of solar and thermal radiation through the canopy, and multiple scattering between the canopy

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Ryan J. MacDonald, James M. Byrne, Stefan W. Kienzle, and Robert P. Larson

1. Introduction Mountains play a key role in the global hydrological cycle and are a main source of water for many of the world’s river systems ( Beniston et al. 1997 ). It is expected that climatic change may have a significant impact on mountain snowpack and, subsequently, the snow-derived water supply ( Barnett et al. 2005 ). Water supply on the western prairies of Canada is highly dependent on snowmelt from the east slopes of the Rocky Mountains ( Schindler and Donahue 2006 ). The potential

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Bin Guan, Duane E. Waliser, Noah P. Molotch, Eric J. Fetzer, and Paul J. Neiman

snowmelt from the seasonal snowpack forms an important water supply during the dry season ( Bales et al. 2006 ). In this regard, the mountain snowpack in the Sierra Nevada provides approximately 75% of the water supply for California’s central valley agricultural sector. An improved understanding of the coupled atmosphere–ocean–land surface processes, which control the timing and magnitude of snow accumulation, is critical for subseasonal (and longer) scale projections of water availability and demand

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Zachary M. Seligman, Joel T. Harper, and Marco P. Maneta

1. Introduction As atmospheric conditions warm during the spring snowmelt season, the energy gains by the snowpack surface outweigh the energy losses. Heat is transferred through the snowpack by diffusive processes and by advection of latent heat, as meltwater generated at the surface percolates downward either along a uniform wetting front or as discrete “pipes,” and refreezes (e.g., Marsh and Woo 1985 ). The added heat initially removes cold content and drives snow grain metamorphism. Once

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Justin R. Minder

1. Introduction Mountain snow maintains glaciers, sets the extent of ecosystems, provides for recreation, and produces major hazards in the form of avalanches. Mountain snowpack is crucial for many communities because it preserves the precipitation that falls during wintertime storms and releases it as runoff, which provides water resources during dry summer months. Globally about one-sixth of the world’s population relies on glaciers and seasonal snow and ice for water resources, much of which

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Mariano H. Masiokas, Ricardo Villalba, Brian H. Luckman, Carlos Le Quesne, and Juan Carlos Aravena

1. Introduction The snowpack accumulated in the central Andes 1 is the main water source of the major rivers in central Chile and central-western Argentina and therefore represents a critical resource for local domestic consumption, irrigation, industries, and hydroelectric generation. Since the main road connecting Santiago, Chile, with Mendoza and Buenos Aires in Argentina crosses the cordillera at these latitudes, snow accumulation also has significant economic impacts on surface

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Vincent Vionnet, Ingrid Dombrowski-Etchevers, Matthieu Lafaysse, Louis Quéno, Yann Seity, and Eric Bazile

processes strongly influencing the snowpack evolution in mountainous terrain (both during accumulation and melting period). Tobin et al. (2012) proposed a method to determine the snowfall limit based on the vertical atmospheric profiles taken from the COSMO, version 2 (COSMO-2), forecasts at 2.2-km grid spacing over the Swiss Alps. Large benefits were also found for the forecasting of precipitation amount. Weusthoff et al. (2010) showed that short-range forecasts of precipitation over the Alps were

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David W. Pierce, Tim P. Barnett, Hugo G. Hidalgo, Tapash Das, Céline Bonfils, Benjamin D. Santer, Govindasamy Bala, Michael D. Dettinger, Daniel R. Cayan, Art Mirin, Andrew W. Wood, and Toru Nozawa

1. Introduction The western United States is an arid region with a large and growing population. Water is a precious resource, and changes in the hydrological cycle have important societal and economic effects. Retention of winter precipitation in the form of snowpack is an integral part of the hydrological cycle in the region. Precipitation from winter storms can be retained in snowpack and released gradually, often months later, in the drier parts of the year. The majority of streamflow in

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