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Mark C. Green, Judith C. Chow, John G. Watson, Kevin Dick, and Daniel Inouye

1. Introduction Wintertime suspended particulate matter with aerodynamic diameters of less than 2.5 μ m (PM 2.5 ) concentrations are frequently higher than normal in many western U.S. valleys. These valleys experience strong temperature inversions, frequently enhanced by the presence of snow cover, and are described as “valley cold pools” ( Whiteman and McKee 1977 , 1978 ; Reeves and Stensrud 2009 ; Silcox et al. 2012 ). Cold-pool stagnation allows a gradual buildup of pollutants over a

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Joseph M. Prusa, Moti Segal, Bradley R. Temeyer, William A. Gallus Jr., and Eugene S. Takle

plume temperature and characteristic outer engine temperature. The exhaust system exit temperatures provided an observational constraint on the exhaust system model sketched in appendix A . The drag coefficient was computed by following the method of Munson et al. (1990) , given the known geometry of the vehicle. Detailed results are presented in the following sections for four driving scenarios: stopped urban traffic (UST), moving urban traffic in heavy snow cover (UHS), moving urban traffic in

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Nikki Vercauteren, Steve W. Lyon, and Georgia Destouni

radiation received at the surface decreases sharply after the growing season and other factors influencing temperature could, thus, become more important. These factors include synoptic meteorology and snow cover, among others ( Stahl et al. 2006 ; Yang et al. 2011 ). Furthermore, snow cover is also itself influenced by insolation and will in turn affect near surface temperature. We therefore here investigate if the solar radiation influences the spatiotemporal snow cover variation in a clear way, and

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Donald C. McKay and George W. Thurtell

MAtCH1978 DONALI) C. McKAY AND GEORGE W. THURTELL 339Measurements of the Energy Fluxes Involved in the Energy Budget of a Snow Cover DONALD C. MCKAY Atmospheric Environment Service, Downsview, Ontario, Canada M3H 5T4 GEORGE W. THURTELLDepartment Land Reso,rce Science, University of Guelph, Guelph, Ontario, Canada N1G 211'1(Manuscript received 11 July 1977, in

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Alan Basist, Norman C. Grody, Thomas C. Peterson, and Claude N. Williams

of snow cover from the same satellite instrument. In order to derive the surface temperature in the microwave spectrum, the variation in surface emissivity must be addressed. The major factor influencing the variation in emissivity is surface wetness, which at 19 GHz (vertical polarization) can lower emissivity by 33%. Therefore, it is necessary to quantitatively determine the perturbation due to surface wetness on the brightness temperature measurements when deriving surface temperature

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C. Prigent, F. Aires, and W. B. Rossow

Introduction The mean monthly land area covered by snow in the Northern Hemisphere ranges from ∼10% to ∼40% during the annual cycle. Because of its high albedo, snow extent is a primary factor controlling the amount of solar radiation absorbed by the earth. Even a shallow snow cover can increase the albedo of a bare landscape from 0.2 to 0.8. Any decrease in snow cover related to a warming trend would result in increased absorption of solar radiation, melting the snow and inducing a positive

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Yves Durand, Gérald Giraud, Martin Laternser, Pierre Etchevers, Laurent Mérindol, and Bernard Lesaffre

1. Introduction This paper is the second part of an extensive climatological based study carried out for the French Alps. For the first time, long-term climate series (temperature, precipitation, and various snow cover parameters) are presented for this area. Based on 40 yr of newly reanalyzed atmospheric model data from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and supplemented by 7 yr of our own French analyses, the Système d’Analyse Fournissant

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Warren Helgason and John W. Pomeroy

local homogeneity, such as forest clearings, meadows, snow-covered frozen lakes, or broad terraces or ridges above the tree line. In ideal situations, the station is located such that the upwind fetch is maximized to ensure adequate distance for the development of an internal boundary layer. The obvious difficulty is that unobstructed fetch lengths are often very limited in mountainous terrain, and therefore siting of instrumentation is often a compromise between characterizing fluxes from important

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Daniel J. Leathers, Daniel Graybeal, Thomas Mote, Andrew Grundstein, and David Robinson

of societal interests. In regions where snow cover is ephemeral, however, the lack of a single seasonal melt, or of consistency in volume or timing, has made forecasting the release of water from the snowpack a formidable challenge, leading to many harmful environmental and societal consequences. Snow cover ablation has been studied in many regions, including the Arctic and sub-Arctic ( Ohmura 1981 ; Braithwaite and Olesen 1990 ; Rowe et al. 1995 ), many high-elevation mountain ranges ( Marks

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Arthur T. DeGaetano, Daniel S. Wilks, and Megan McKay

JUNE 1996 DEGAETANO ET AL. 1009A Physically Based Model of Soil Freezing in Humid Climates Using Air Temperature and Snow Cover DataARTHUR T. DEGAETANO, DANIEL S. WILKS, AND MEGAN MCI~-Northeast Regional Climate Center, Cornell University, Ithaca, New York(Manuscript received 31 August 1995, in final form 12 December 1995)ABSTRACT A one-dimensional heat flow model is

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