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Land surface heat exchange over snow and frozen soil
KTH, Superseded Departments, Land and Water Resources Engineering.
2001 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The energy exchange in the soil-snow-vegetation-atmospheresystem was studied to improve the quantitative knowledge of thegoverning processes. The lack of such knowledge contributes tothe uncertainty in the applicability of many existing modelsindependent of the temporal or spatial scale. The theoreticalbackground and available methods for measurements and numericalsimulations were reviewed. Numerical simulation models andavailable data sets representing open land and boreal forestwere evaluated in both diurnal and seasonal time-scales.Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden over two winters, 1997-1999. Twoone-dimensional simulation models of different complexity wereused to simulate the heat and water transfer in thesoil-snow-atmosphere system and compared with the measurements.Comparison of simulated and observed heat fluxes showed thatparameter values governing the upper boundary condition weremore important than the formulation of the internal mass andheat balance of the snow cover. The models were useful toevaluate the lack of energy balance closure in the observedsurface heat fluxes, which underlined the importance ofimproved accuracy in eddy correlation measurements of latentflow during winter conditions.

The representation of boreal forest in the land surfacescheme used within a weather forecast model was tested with athree-year data set from the NOPEX forest site in centralSweden. The formulation with separate energy balances forvegetation and the soil/snow beneath tree cover improvedsimulation of the seasonal and diurnal variations of latent andsensible heat flux compared with an older model version.Further improvements of simulated surface heat fluxes could beexpected if the variation of vegetation properties within andbetween years and a new formulation of the boundary conditionsfor heat flux into the soil is included.

Keywords: Surface energy balance, Snow, Boreal forest,SVAT models, Eddy-correlation Measurements, Latent heat flux,Sensible heat flux, Net radiation, Soil temperature,Aerodynamic roughness, Surface resistance

Place, publisher, year, edition, pages
Stockholm: KTH , 2001. , iv, 14 p.
Series
Trita-AMI. LIC, 2068
Keyword [en]
Surface energy balance, Snow, Boreal forest, SVAT models, Eddy-correlation Measurements, Latent heat flux, Sensible heat flux, Net radiation, Soil temperature, Aerodynamic roughness, Surface resistance
National Category
Civil Engineering
Identifiers
URN: urn:nbn:se:kth:diva-1231ISBN: 91-7283-061-1 (print)OAI: oai:DiVA.org:kth-1231DiVA: diva2:7030
Note
QC 20100614Available from: 2001-06-18 Created: 2001-06-18 Last updated: 2010-06-14Bibliographically approved
List of papers
1. The energy exchange at the land surface during winter: existing theories and their limitations
Open this publication in new window or tab >>The energy exchange at the land surface during winter: existing theories and their limitations
(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13340 (URN)
Note
QC 20100614Available from: 2010-06-14 Created: 2010-06-14 Last updated: 2010-06-14Bibliographically approved
2. The surface energy balance of a snow cover: comparing measurements to two different simulation models
Open this publication in new window or tab >>The surface energy balance of a snow cover: comparing measurements to two different simulation models
2001 (English)In: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 70, no 1-4, 81-96 p.Article in journal (Refereed) Published
Abstract [en]

We compared two one-dimensional simulation models for heat and water fluxes in the soil-snow-atmosphere system with respect to their mathematical formulations of the surface heat exchange and the snow pack evolution. They were chosen as examples of a simple one-layer snow model and a more detailed multiple-layer snow model (SNTHERM). The snow models were combined with the same one-dimensional model for the heat and water balance of the underlying soil (CoupModel). Data from an arable field in central Sweden (Marsta), covering two years (1997-1999) of soil temperature, snow depth and eddy-correlation measurements were successfully compared with the models. Conditions with a snow pack deeper or shallower than 10cm and bare soil resulted in similar discrepancies. The simulated net radiation and sensible heat flux were in good agreement with that measured during snow-covered periods, except for situations with snowmelt when the downward sensible heat flux was overestimated by 10-20 WM-2. The results showed that the uncertainties in parameter values were more important than the model formulation and that both models were useful in evaluating the limitations and uncertainties of the measurements.

Keyword
LAND, PARAMETERIZATION, TEMPERATURE, RADIATION, WATER, SOIL
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-13341 (URN)10.1007/s007040170007 (DOI)000172271800007 ()
Note
QC 20100614Available from: 2010-06-14 Created: 2010-06-14 Last updated: 2017-12-12Bibliographically approved
3. Boreal-forest surface parameterisation in the ECMWF model: 1D test with NOPEX long-term data.
Open this publication in new window or tab >>Boreal-forest surface parameterisation in the ECMWF model: 1D test with NOPEX long-term data.
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-13342 (URN)
Note
QC 20100614Available from: 2010-06-14 Created: 2010-06-14 Last updated: 2010-06-14Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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  • Other locale
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