A Sensitivity Study of Daytime Net Radiation during Snowmelt to Forest Canopy and Atmospheric Conditions

Sicart, J.; Essery, Richard; Pomeroy, John W.; Hardy, Janet P.; Link, Timothy E.; Marks, Danny

doi:10.1175/1525-7541(2004)005<0774:assodn>2.0.co;2

Cited by 146 publications

(187 citation statements)

References 34 publications

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“…Bewley et al 2007). Whereas vegetation can shade snow on the ground from solar radiation, it can also greatly increase the net thermal radiation absorbed by snow (Sicart et al 2004). Moreover, sun-lit vegetation can have temperatures well in excess of the air and snow temperatures, further increasing the thermal radiation emitted to the snow (Pomeroy et al 2009).…”

Section: Callaghan and Tweedie 2011)mentioning

confidence: 99%

Multiple Effects of Changes in Arctic Snow Cover

Callaghan

Johansson

Brown

et al. 2011

AMBIO

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187

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Snow cover plays a major role in the climate, hydrological and ecological systems of the Arctic and other regions through its influence on the surface energy balance (e.g. reflectivity), water balance (e.g. water storage and release), thermal regimes (e.g. insulation), vegetation and trace gas fluxes. Feedbacks to the climate system have global consequences. The livelihoods and well-being of Arctic residents and many services for the wider population depend on snow conditions so changes have important consequences. Already, changing snow conditions, particularly reduced summer soil moisture, winter thaw events and rain-on-snow conditions have negatively affected commercial forestry, reindeer herding, some wild animal populations and vegetation. Reductions in snow cover are also adversely impacting indigenous peoples' access to traditional foods with negative impacts on human health and well-being. However, there are likely to be some benefits from a changing Arctic snow regime such as more even run-off from melting snow that favours hydropower operations.

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Section: Callaghan and Tweedie 2011)mentioning

confidence: 99%

Multiple Effects of Changes in Arctic Snow Cover

Callaghan

Johansson

Brown

et al. 2011

AMBIO

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187

107

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“…Snowpacks within a forest are subject to a complicated radiative environment due to longwave radiant emission from tree boles and the overlying canopy, as well as shading the snowpack surface from incoming shortwave radiation (Male and Granger 1981;DeWalle and Rango 2008;Pomeroy et al 2009;Lawler and Link 2011;Musselman et al 2012a,b). Sicart et al (2004) found that the effect of enhanced longwave and decreased shortwave radiation balanced the subcanopy daily net radiation for a wide range of canopy densities (in dense forests). In addition to radiative effects, forests shelter the snowpack from winds, thus reducing turbulent fluxes to and from the surface by an order of magnitude (Blanken et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…More information about Eq. (4) and discussions about subcanopy net shortwave radiation are provided elsewhere (e.g., Sicart et al 2004;DeWalle and Rango 2008;Pomeroy et al 2009, and references therein).…”

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Snow Temperature Changes within a Seasonal Snowpack and Their Relationship to Turbulent Fluxes of Sensible and Latent Heat

Burns

Molotch

Williams

et al. 2014

Journal of Hydrometeorology

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Snowpack temperatures from a subalpine forest below Niwot Ridge, Colorado, are examined with respect to atmospheric conditions and the 30-min above-canopy and subcanopy eddy covariance fluxes of sensible Q h and latent Q e heat. In the lower snowpack, daily snow temperature changes greater than 18C day 21 occurred about 1-2 times in late winter and early spring, which resulted in transitions to and from an isothermal snowpack. Though air temperature was a primary control on snowpack temperature, rapid snowpack warm-up events were sometimes preceded by strong downslope winds that kept the nighttime air (and canopy) temperature above freezing, thus increasing sensible heat and longwave radiative transfer from the canopy to the snowpack. There was an indication that water vapor condensation on the snow surface intensified the snowpack warm-up. In late winter, subcanopy Q h was typically between 210 and 10 W m 22 and rarely had a magnitude larger than 20 W m 22 . The direction of subcanopy Q h was closely related to the canopy temperature and only weakly dependent on the time of day. The daytime subcanopy Q h monthly frequency distribution was near normal, whereas the nighttime distribution was more peaked near zero with a large positive skewness. In contrast, above-canopy Q h was larger in magnitude (100-400 W m 22 ) and primarily warmed the forest-surface at night and cooled it during the day. Around midday, decoupling of subcanopy and above-canopy air led to an apparent cooling of the snow surface by sensible heat. Sources of uncertainty in the subcanopy eddy covariance flux measurements are suggested. Implications of the observed snowpack temperature changes for future climates are discussed.

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“…We assumed the sensitivity of the VIS/NIR ratio to be 5% in our numerical experiments simply because the instrument accuracy for solar radiation observation is around 5% (Sicart et al, 2004). In the following sections, we refer to the sensitivity experiments as VIS0.45, VIS0.50, and VIS0.55 runs when the energy in the VIS band composes 45%, 50%, and 55% of the total incident solar radiation, respectively.…”

Section: Experiments Designmentioning

confidence: 99%

Numerical simulation of sensitivities of snow melting to spectral composition of the incoming solar radiation

Sun

Wang

et al. 2009

Adv. Atmos. Sci.

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Snow albedo is an important factor influencing the snow surface energy budget and snow melting, yet uncertainties remain in the calculation of spectrally resolved snow surface albedo because the spectral composition (visible versus near infrared) of the incident solar radiation is seldom available. The influence of the spectral composition of the incoming solar radiation on the snow surface albedo, snow surface energy budget, and final snow ablation is investigated through sensitivity experiments of four snow seasons at two open sites in the Alps by using a multi-layer Snow-Atmosphere-Soil-Transfer scheme (SAST). Since the snow albedo in the near infrared (NIR) spectral band is significantly lower than that in the visible (VIS) band, and almost the entire NIR part of the solar radiation is absorbed in the top layer of the snow pack, given a fixed amount of incoming solar radiation, a lower VIS/NIR ratio implies that more NIR radiation is reaching the ground surface and more is absorbed by the top layer of the snow pack, therefore, speeding up the snow melting and increasing the surface runoff, although a lesser part of the solar radiation in the visible band is transmitted into and trapped by the sub-layer of the snow pack. The above VIS/NIR ratio effect of the incoming solar radiation can result in a couple of days difference in the timing of snow ablation and it becomes more significant in late spring when the total solar radiation is intensified with seasonal evolution. Snow aging also slightly intensifies this VIS/NIR ratio effect.Key words: simulation, snow albedo, snow melt, spectral composition, solar radiation Citation: Li, W. P., S. F. Sun, B. Wang, and X. Liu, 2009: Numerical simulation of sensitivities of snow melting to spectral composition of the incoming solar radiation.

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A Sensitivity Study of Daytime Net Radiation during Snowmelt to Forest Canopy and Atmospheric Conditions

Cited by 146 publications

References 34 publications

Multiple Effects of Changes in Arctic Snow Cover

Multiple Effects of Changes in Arctic Snow Cover

Snow Temperature Changes within a Seasonal Snowpack and Their Relationship to Turbulent Fluxes of Sensible and Latent Heat

Numerical simulation of sensitivities of snow melting to spectral composition of the incoming solar radiation

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