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

as well as canopy structure. As view angles increase away from nadir, less of the ground surface is visible in forested areas. Similarly, as the canopy cover of a forest increases, the VGF will also decrease. A quantitative understanding of these effects requires development of a model for the way the VGF varies as a function of view angle, forest canopy properties, and topography. Prior results indicate a geometric optical (GO) model captures the basic shape of the relationship between the VGF

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Robert E. Davis, Thomas H. Painter, Rick Forster, Don Cline, Richard Armstrong, Terry Haran, Kyle McDonald, and Kelly Elder

limiting the recovery of snow properties and freeze–thaw timing. We summarize here the primary spaceborne remote sensing data collected during the CLPX in four classes of sensing modality—multispectral and hyperspectral optical, and passive and active microwave—that will be used in conjunction with the airborne remote sensing and field data in further investigations. 2. Multispectral optical imaging Pure snow has a distinctive spectral signature in the reflective solar spectrum, is one of the brightest

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Don Cline, Simon Yueh, Bruce Chapman, Boba Stankov, Al Gasiewski, Dallas Masters, Kelly Elder, Richard Kelly, Thomas H. Painter, Steve Miller, Steve Katzberg, and Larry Mahrt

February 2002, IOP2 from 24 to 30 March 2002, IOP3 from 17 to 25 February 2003, and IOP4 from 25 March through 1 April 2003. In this paper, we summarize the CLPX airborne remote sensing datasets from four categories that span three spectral regions: gamma radiation observations, multi- and hyperspectral optical imaging and optical altimetry, and passive and active microwave. 2. Gamma radiation snow and soil moisture surveys Natural terrestrial gamma radiation is emitted from the potassium, uranium, and

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Janet Hardy, Robert Davis, Yeohoon Koh, Don Cline, Kelly Elder, Richard Armstrong, Hans-Peter Marshall, Thomas Painter, Gilles Castres Saint-Martin, Roger DeRoo, Kamal Sarabandi, Tobias Graf, Toshio Koike, and Kyle McDonald

the optical airborne and spaceborne imaging spectrometers and the multispectral imagers used in the CLPX. These measurements will also be compared with field microwave measurements for synthesizing the models’ snow properties, including grain size, albedo, and surface liquid water content. e. Microwave radiometer systems The University of Michigan Radiation Laboratory managed a passive microwave radiometer system that operated at 1.4, 6.7, 19, and 37 GHz. These systems measured radiometric

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

using up- and down-looking pyranometers and pyrgeometers for shortwave and longwave, respectively. Pyrgeometers were also deployed at 4 and 25 m above the ground surface to evaluate longwave radiative flux divergence. Soil measurements include three levels of temperature (0.025, 0.05, and 0.10 m), two levels of moisture (0.05 and 0.10 m), and a heat flux measurement at 0.10 m. A probe capable of measuring thermal properties of the soil was installed to determine heat capacity and thermal

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John Pomeroy, Chad Ellis, Aled Rowlands, Richard Essery, Janet Hardy, Tim Link, Danny Marks, and Jean Emmanuel Sicart

radiative transfer modeling. 2. Variability of shortwave transmission through forest canopies Forested landscapes have a large spatial distribution of ablation energy because this energy varies according to the structural properties of the canopy [e.g., density, Davis et al. (1997) ; leaf area index, Pomeroy and Granger (1997) ]. Transmittance through canopies with relatively small sky view factors can be estimated using the assumption of isotropic scattering by canopy elements; however, it is

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

Transfer Model Intercomparison ( Pinty et al. 2004 ) found that such models now compare well for homogeneous canopies but still have large discrepancies for complex heterogeneous canopies. These models are also computationally expensive and require large amounts of data on canopy structure and the optical properties of canopy elements. A great deal of work on small-scale radiative transfer through heterogeneous canopies has used statistical models that assume random tree distributions or spatially

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Susan Frankenstein, Anne Sawyer, and Julie Koeberle

. Data Field data to which the model output were compared were collected during the winter of 2002–2003 as part of the National Aeronautics and Space Administration’s (NASA) Cold Land Processes Experiment (CLPX). CLPX was developed to identify the role of snowpack in the storage of water resources by quantifying many snowpack properties, improve the representation of snow in models by taking measurements on various distributed spatial and temporal scales, provide high-quality and abundant databases

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Nick Rutter, Don Cline, and Long Li

physics by comparing snow water equivalent (SWE), snow depth, and snow temperature, simulated in a one-dimensional mode at five sites in Colorado, with independent in situ observations from the National Aeronautics and Space Administration (NASA) Cold Land Processes Field Experiment (CLPX, Elder et al. 2008b ). Here we are interested in the ability of the physical formulations and algorithms in the NSM to accurately simulate the evolution of these key snowpack properties, given accurately observed

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