An assessment of measurements and modeling of turbulent fluxes over snow by eddy covariance at two complex mountain sites


Reba, Michele L.. (2008). An assessment of measurements and modeling of turbulent fluxes over snow by eddy covariance at two complex mountain sites. Theses and Dissertations Collection, University of Idaho Library Digital Collections.

An assessment of measurements and modeling of turbulent fluxes over snow by eddy covariance at two complex mountain sites
Reba, Michele L.
Snow--Idaho--Reynolds Creek Watershed--Measurement Runoff--Mathematical models
Civil Engineering
Snow is a major component of the annual water balance in many locations across the globe, including the mountainous regions of the interior western U.S. and Canada. As water is scarce and over-allocated in many parts of this region, it is of the utmost importance to accurately model the amount and timing of spring runoff. Most components of snow cover energy and mass balance models are validated through direct measurements such as snow water equivalent, density, temperature, and net radiation. However, validation data for turbulent fluxes are generally limited. Eddy covariance (EC) is the most direct method to measure turbulent fluxes. Findings from this research are based on EC and meteorological measurements from two mountain sites, a wind-exposed and a sheltered sub-canopy, during the 2004, 2005, and 2006 snow seasons.;EC systems have been used successfully over snow in mountain regions but detailed analysis of post-processing and data quality is lacking. The first component of this research focuses on the viability of EC technology over snow in mountainous terrain and makes a detailed analysis of data quality and the influence post-processing has on turbulent fluxes. Post-processing and data quality analysis of these data indicate that application of EC-technology at these sites was viable and data quality parameters were comparable to other reported eddy flux research.;As detailed analysis of site characteristics on EC measurements over snow is limited, this research then generalizes findings at two contrasting sites and highlights the challenges of measuring EC over snow. The exposed site yielded measured sensible and latent heat fluxes that were respectively five and two times the magnitude of those at the sheltered site. There was less inter-annual variability in EC-measured turbulent fluxes at the sheltered compared to the exposed site. Differences between sites are explored at seasonal, monthly and event based temporal scales. These findings highlight the importance of careful review of over-snow EC-measured fluxes and the meteorological conditions during which those measurements were conducted.;Improved modeling of the snow cover that is based on physical processes instead of on empirical relationships between climate and snowcover dynamics should better predict responses to climatic variability and trends. Measured turbulent fluxes are used to determine key model parameters and update the stability functions of an existing snow cover and energy balance model to improve simulated latent heat flux while retaining accuracy in simulating snow water equivalent. The adjustable parameters of roughness length and active layer depth influenced the accuracy with which the model simulated mass and latent heat flux. At the exposed site shorter roughness lengths and a thicker active layer was optimal, while longer roughness lengths and a thinner active layer was optimal at the sheltered site. These outcomes are related to the site characteristics and can be readily incorporated into a distributed snowmelt model.
Thesis (Ph. D., Civil Engineering)--University of Idaho, December 2008.
Major Professor:
Timothy E. Link.
Defense Date:
December 2008.
Format Original:
xiii, 120 leaves :col. ill., col. maps ;29 cm.

Contact us about this record

In Copyright - Educational Use Permitted. For more information, please contact University of Idaho Library Special Collections and Archives Department at
Standardized Rights: