Spatial Variability of Shortwave Irradiance for Snowmelt in Forests

John Pomeroy Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Search for other papers by John Pomeroy in
Current site
Google Scholar
PubMed
Close
,
Chad Ellis Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Search for other papers by Chad Ellis in
Current site
Google Scholar
PubMed
Close
,
Aled Rowlands Institute of Geography and Earth Science, University of Wales, Aberystwyth, Ceredigion, United Kingdom

Search for other papers by Aled Rowlands in
Current site
Google Scholar
PubMed
Close
,
Richard Essery Institute of Geography and Earth Science, University of Wales, Aberystwyth, Ceredigion, United Kingdom

Search for other papers by Richard Essery in
Current site
Google Scholar
PubMed
Close
,
Janet Hardy U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire

Search for other papers by Janet Hardy in
Current site
Google Scholar
PubMed
Close
,
Tim Link Department of Forest Resources, University of Idaho, Moscow, Idaho

Search for other papers by Tim Link in
Current site
Google Scholar
PubMed
Close
,
Danny Marks Northwest Watershed Research Center, Agricultural Research Service, USDA, Boise, Idaho

Search for other papers by Danny Marks in
Current site
Google Scholar
PubMed
Close
, and
Jean Emmanuel Sicart Great Ice, Institut de Recherche pour le Développement, Montpellier, France

Search for other papers by Jean Emmanuel Sicart in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The spatial variation of melt energy can influence snow cover depletion rates and in turn be influenced by the spatial variability of shortwave irradiance to snow. The spatial variability of shortwave irradiance during melt under uniform and discontinuous evergreen canopies at a U.S. Rocky Mountains site was measured, analyzed, and then compared to observations from mountain and boreal forests in Canada. All observations used arrays of pyranometers randomly spaced under evergreen canopies of varying structure and latitude. The spatial variability of irradiance for both overcast and clear conditions declined dramatically, as the sample averaging interval increased from minutes to 1 day. At daily averaging intervals, there was little influence of cloudiness on the variability of subcanopy irradiance; instead, it was dominated by stand structure. The spatial variability of irradiance on daily intervals was higher for the discontinuous canopies, but it did not scale reliably with canopy sky view. The spatial variation in irradiance resulted in a coefficient of variation of melt energy of 0.23 for the set of U.S. and Canadian stands. This variability in melt energy smoothed the snow-covered area depletion curve in a distributed melt simulation, thereby lengthening the duration of melt by 20%. This is consistent with observed natural snow cover depletion curves and shows that variations in melt energy and snow accumulation can influence snow-covered area depletion under forest canopies.

Corresponding author address: John Pomeroy, Centre for Hydrology, University of Saskatchewan, 117 Science Place, Saskatoon SK S7N5CB, Canada. Email: john.pomeroy@usask.ca

This article included in the The Cold Land Processes Experiment (CLPX) special collection.

Abstract

The spatial variation of melt energy can influence snow cover depletion rates and in turn be influenced by the spatial variability of shortwave irradiance to snow. The spatial variability of shortwave irradiance during melt under uniform and discontinuous evergreen canopies at a U.S. Rocky Mountains site was measured, analyzed, and then compared to observations from mountain and boreal forests in Canada. All observations used arrays of pyranometers randomly spaced under evergreen canopies of varying structure and latitude. The spatial variability of irradiance for both overcast and clear conditions declined dramatically, as the sample averaging interval increased from minutes to 1 day. At daily averaging intervals, there was little influence of cloudiness on the variability of subcanopy irradiance; instead, it was dominated by stand structure. The spatial variability of irradiance on daily intervals was higher for the discontinuous canopies, but it did not scale reliably with canopy sky view. The spatial variation in irradiance resulted in a coefficient of variation of melt energy of 0.23 for the set of U.S. and Canadian stands. This variability in melt energy smoothed the snow-covered area depletion curve in a distributed melt simulation, thereby lengthening the duration of melt by 20%. This is consistent with observed natural snow cover depletion curves and shows that variations in melt energy and snow accumulation can influence snow-covered area depletion under forest canopies.

Corresponding author address: John Pomeroy, Centre for Hydrology, University of Saskatchewan, 117 Science Place, Saskatoon SK S7N5CB, Canada. Email: john.pomeroy@usask.ca

This article included in the The Cold Land Processes Experiment (CLPX) special collection.

Save
  • Anderson, M. C., 1966: Stand structure and light penetration. II. A theoretical analysis. J. Appl. Ecol., 3 , 4154.

  • Brubaker, K. L., and Menoes M. , 2001: A technique to estimate snow depletion curves from time-series data using the beta distribution. Proc. 58th Annual Eastern Snow Conf., Ottawa, ON, Canada, ESC and Canadian Geophysical Union, 343–346.

    • Search Google Scholar
    • Export Citation
  • Buttle, J. M., and McDonnell J. J. , 1987: Modelling the areal depletion of snowcover in a forested catchment. J. Hydrol., 90 , 4360.

  • Cline, D., and Coauthors, 2002: Overview of the NASA cold land processes field experiment (CLPX-2002). Microwave Remote Sensing of the Atmosphere and Environment III, C. D. Kummerow, J. Jiang, and S. Uratuka, Eds., International Society for Optical Engineering (SPIE Proceedings, Vol. 4894), 361–372.

    • Search Google Scholar
    • Export Citation
  • Davis, R. E., Hardy J. P. , Ni W. , Woodcock C. , McKenzie J. C. , Jordan R. , and Li X. , 1997: Variation of snow cover ablation in the boreal forest: A sensitivity study on the effects of conifer canopy. J. Geophys. Res., 102 , 2938929395.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Donald, J. R., Soulis E. D. , Kouwen N. , and Pietroniro A. , 1995: A land cover-based snow cover representation for distributed hydrological models. Water Resour. Res., 31 , 9951009.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Eagleson, P. S., 2002: Ecohydrology: Darwinian Expression of Vegetation Form and Function. Cambridge University Press, 443 pp.

  • Ellis, C. R., and Pomeroy J. W. , 2007: Estimating sub-canopy shortwave irradiance to melting snow on forested slopes. Hydrol. Processes, 21 , 25812593.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Essery, R. L. H., and Pomeroy J. W. , 2004: Implications of spatial distributions of snow mass and melt rate for snow-cover depletion: Theoretical considerations. Ann. Glaciol., 38 , 261265.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Essery, R. L. H., and Coauthors, 2008: Radiative transfer modeling of a coniferous canopy characterized by airborne remote sensing. J. Hydrometeor., 9 , 228241.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Faria, D. A., Pomeroy J. W. , and Essery R. L. H. , 2000: Effect of covariance between ablation and snow water equivalent on depletion of snow-covered area in a forest. Hydrol. Processes, 14 , 26832695.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gray, D. M., and Landine P. G. , 1988: An energy-budget snowmelt model for the Canadian Prairies. Can. J. Earth Sci., 25 , 12921303.

  • Hardy, J. P., Melloh R. A. , Robinson P. , and Jordan R. , 2000: Incorporating effects of forest litter in a snow process model. Hydrol. Processes, 14 , 32273237.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hardy, J. P., Melloh R. A. , Koenig G. , Marks D. , Winstral A. , Pomeroy J. W. , and Link T. , 2004: Solar radiation transmission through conifer canopies. Agric. For. Meteor., 126 , 257270.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jarvis, P. G., James G. B. , and Landsberg J. J. , 1975: Coniferous forest. Case Studies, J. L. Monteith, Ed., Vol. 2, Vegetation and the Atmosphere, Academic Press, 171–240 pp.

    • Search Google Scholar
    • Export Citation
  • Link, T. E., and Marks D. , 1999: Point simulation of seasonal snow cover dynamics beneath boreal forest canopies. J. Geophys. Res., 104 , 841858.

    • Search Google Scholar
    • Export Citation
  • Link, T. E., Hardy J. P. , and Marks D. , 2004: A deterministic method to characterize canopy radiative transfer properties. Hydrol. Processes, 18 , 35833594.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marks, D., and Winstral A. , 2001: Comparison of snow deposition, the snow cover energy balance, and snowmelt at two sites in a semiarid mountain basin. J. Hydrometeor., 2 , 213227.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marks, D., Domingo J. , Susong D. , Link T. , and Garen D. , 1999: A spatially distributed energy balance snowmelt model for application in mountain basins. Hydrol. Processes, 13 , 19351959.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nilson, T. A., 1971: A theoretical analysis of the frequency of gaps in plant stands. Agric. For. Meteor., 8 , 2538.

  • Parker, G. G., Davis M. , and Moon Chapotin S. , 2002: Canopy light transmittance in Douglas-fir–western hemlock stands. Tree Physiol., 22 , 147157.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pomeroy, J. W., and Granger R. J. , 1997: Sustainability of the western Canadian boreal forest under changing hydrological conditions. I. Snow accumulation and ablation. Proc.Sustainability of Water Resources under Increasing UncertaintySymp., Rabat, Morocco, Int. Commission on Water Resource Systems and Cosponors, IAHS Publication 240, 237–242.

    • Search Google Scholar
    • Export Citation
  • Pomeroy, J. W., Gray D. M. , Shook K. R. , Toth B. , Essery R. L. H. , Pietroniro A. , and Hedstrom N. , 1998: An evaluation of snow accumulation and ablation processes for land surface modelling. Hydrol. Processes, 12 , 23392367.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pomeroy, J. W., Hanson S. , and Faria D. A. , 2001: Small-scale variation in snowmelt energy in a boreal forest: An additional factor controlling depletion of snow cover? Proc. 58th Annual Eastern Snow Conf., Ottawa, ON, Canada, ESC and Canadian Geophysical Union, 85–96.

    • Search Google Scholar
    • Export Citation
  • Pomeroy, J. W., Essery R. L. H. , and Toth B. , 2004: Implications of spatial distributions of snow mass and melt rate on snow-cover depletion: Observations in a subarctic mountain catchment. Ann. Glaciol., 38 , 195201.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pukkala, T., Becker T. , Kuuluvainen T. , and Oker-Blom P. , 1991: Predicting spatial distribution of direct radiation below forest canopies. Agric. For. Meteor., 55 , 295307.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ross, M. S., Flanagan L. B. , and La Roi G. H. , 1986: Seasonal and successional changes in light quality and quantity in the understory of boreal forest ecosystems. Can. J. Bot., 64 , 27922799.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roujean, J-L., 1999: Measurements of PAR transmittance within boreal forest stands during BOREAS. Agric. For. Meteor., 93 , 16.

  • Satterlund, D. R., 1983: Forest shadows: How much shelter in a shelterwood? For. Ecol. Manage., 5 , 2337.

  • Shook, K., 1995: Simulation of the ablation of prairie snowcovers. Ph.D. thesis, University of Saskatchewan, 189 pp.

  • Shook, K., Pomeroy J. W. , and Gray D. M. , 1993: Temporal variation in snow-covered area during melt in Prairie and Alpine environments. Nord. Hydrol., 24 , 183198.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sicart, J. E., Pomeroy J. W. , Essery R. L. H. , Hardy J. E. , Link T. , and Marks D. , 2004: A sensitivity study of daytime net radiation during snowmelt to forest canopy and atmospheric conditions. J. Hydrometeor., 5 , 774784.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 852 354 9
PDF Downloads 124 56 9