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D. Marks, A. Winstral, G. Flerchinger, M. Reba, J. Pomeroy, T. Link, and K. Elder

, snow cover, and weather conditions: the early period was cold and dry, although the snow cover doubled in mass; the mid period was a transition from cold to warmer conditions; and the late period represented active melting conditions during the final ablation of the snow cover ( Fig. 1 ). The eddy covariance method uses measurements of vertical fluxes in the surface boundary layer. Eddy covariance measures the flux directly by sensing the properties of eddies as they pass through a measurement

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

-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) or the Weather Research and Forecasting (WRF) Model can also be used for a 4D variational application if lateral boundary conditions are not critical]. The LAPS analysis is a series of routines that then takes the local observations with other nationally disseminated data and modifies the background field to match those observations. In addition, quality control measures (buddy checking and weighting by measurement

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Glen E. Liston and Christopher A. Hiemstra

patterns, but the magnitudes are often deficient. This error can be the result of limitations in the model physics, errors in meteorological forcing (e.g., snow precipitation; Liston and Sturm 2004 ), and deficiencies in boundary conditions [e.g., relatively low-resolution topography and vegetation data; Liston and Sturm (1998) ; Hiemstra et al. (2006) ; Liston et al. (2007) ]. These inadequacies can propagate the associated errors in many ways ( Burrough and McDonnell 1998 ). For example

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Nick Rutter, Don Cline, and Long Li

), and 2) the Utah Energy Balance Model (UEB; Tarboton and Luce 1996 ). Table 1 illustrates that both models have been extensively evaluated in a wide range of hydroclimatological conditions in terrestrial and marine environments. The NSM exploits the strengths of these models, notably the physical algorithms used by SNTHERM to solve all soil–snow–atmosphere mass and energy fluxes, other than the solution of snow surface temperature, which follows conventions of the UEB model. Euler predictor

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Rafał Wójcik, Konstantinos Andreadis, Marco Tedesco, Eric Wood, Tara Troy, and Dennis Lettenmeier

eigenvalues and eigenvectors technique (e.g., Jin 1993 ). The brightness temperatures are obtained by considering the boundary conditions, which provide the weights of the elements of the base of eigenvectors. c. The Microwave Emission Model of Layered Snowpack model In MEMLS ( Mätzler and Wiesmann 1999 ; Wiesmann and Mätzler 1999 ), the snow cover is thought to be a stack of horizontal layers. Each layer is characterized by a thickness, a correlation length, its density, liquid water content, and

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Susan Frankenstein, Anne Sawyer, and Julie Koeberle

vapor condensation/evaporation, respectively. The terms on the right-hand side incorporate temperature changes due to vertical heat conduction, water, and vapor flow, as well as plant uptake/release. The boundary conditions at the soil/snow and vegetation (crops, grass, shrubs, and so on) surfaces are where T g is the ground/snow surface temperature (K); T f is the foliage surface temperature (K); ɛ g is the ground/snow emissivity; α g is the shortwave albedo of the ground

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Richard Essery, Peter Bunting, Aled Rowlands, Nick Rutter, Janet Hardy, Rae Melloh, Tim Link, Danny Marks, and John Pomeroy

while providing good definition of the forest boundary in denser areas. Four main techniques have been developed for automatic crown delineation in images: valley following ( Gougeon 1995 ), pattern matching ( Pollock 1996 ), crown centroid identification ( Culvenor 2002 ), and wavelet analysis ( Strand et al. 2006 ). The crown centroid method used here is described by Bunting and Lucas (2006) . Local maxima in NDVI are identified as crown centers and expanded to minima to form crown edges. A

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Kelly Elder, Angus Goodbody, Don Cline, Paul Houser, Glen E. Liston, Larry Mahrt, and Nick Rutter

temperature. Snow depth, soil moisture and soil temperature are measured at select sites. The CLPX small regional study area (SRSA) includes 40 SNOTEL sites. Two sites lay within the Fraser MSA and four lay within the Rabbit Ears MSA. The tower at the SNOTEL site is inside the boundaries of the Buffalo Pass ISA. Data from these sites are offered on a near-real-time basis, and historical data are accessed from the NRCS Water and Climate Center Web site (available online at www.wcc.nrcs.usda.gov ). c. U

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Kelly Elder, Don Cline, Glen E. Liston, and Richard Armstrong

loading to the thermometer stem. Thermometers were calibrated periodically in an ice bath throughout the experiment. The precision for the thermometers was 1°C, and the accuracy was ±1°C. 3) Snow stratigraphy Stratigraphy was recorded for major layers in the snowpack. Vertical delineation of the major layers was determined by subjective methods including grain type and size, snow strength, and boundaries such as ice lenses and crusts. Both grain type and size were recorded for major layers; they were

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Jicheng Liu, Curtis E. Woodcock, Rae A. Melloh, Robert E. Davis, Ceretha McKenzie, and Thomas H. Painter

centers in this model are assumed to be randomly located, following a uniform distribution between heights h 1 and h 2 , the lower and upper boundaries of the heights of crown centers, respectively ( Fig. 3 ). Within each crown, the foliage and branches are assumed uniformly distributed with a specified foliage area volume density. The effect of topography can be taken into account in the GORT model by using several simple transformations in coordinate space ( Schaaf et al. 1994 ). The GORT model

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