Local‐Scale Advection of Sensible and Latent Heat During Snowmelt

Harder, Phillip; Pomeroy, John W.; Helgason, Warren

doi:10.1002/2017gl074394

Cited by 36 publications

(70 citation statements)

References 24 publications

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“…Patchy snow cover can lead to the horizontal transport of sensible and latent heat between snow-free and snow-covered areas (Harder, Pomeroy, & Helgason, 2017;Mott, Daniels, & Lehning, 2015). This advection has implications for the processes involved in the development of the snowpack as well as the representativeness and validity of turbulent flux measurements (Granger, Essery, & Pomeroy, 2006;Mott et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Energy balance and snowmelt drivers of a marginal subalpine snowpack

Bilish

McGowan

Callow

2018

Hydrological Processes

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Snowmelt from the seasonal snowpack in the Australian Alps is a significant source of water for irrigated agriculture, electricity generation, and environmental flows in the Murray–Darling Basin. Previous studies have reported negative decadal to multidecadal trends in maximum snow depth, snow season duration, and snow‐covered area. Here, we characterise the energy balance of this marginal maritime snowpack for the first time. Turbulent fluxes measured using the eddy covariance and bulk aerodynamic methods are compared; discrepancies are attributed to the differing assumptions of the methods and characteristics of the measurement site. We examine the variability of the individual energy balance components and the drivers of snowmelt, and we find that incoming longwave radiation is the dominant control on snowmelt, providing more than 80% of the total energy to the snowpack over the season. During a midwinter rain‐on‐snow event, the advected rain heat flux provided 8% of the daily total, with the incoming longwave flux still accounting for almost 80%. The ground heat flux contributes a small proportion of the seasonal total but increases in patchy or intermittent snow cover. Comparing these results with those of studies in other maritime locations, we find that the turbulent fluxes are likely to make a proportionally higher contribution to the energy balance due to the short Australian snow season, underpinning the sensitivity of this environment to climate variability and change. These results extend the limited body of knowledge on highly marginal snowpacks and may be relevant to other regions with no direct measurements of the energy balance.

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Section: Introductionmentioning

confidence: 99%

Energy balance and snowmelt drivers of a marginal subalpine snowpack

Bilish

McGowan

Callow

2018

Hydrological Processes

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“…The deficiency of these modelling approaches is that none have been validated with observations of advection nor do they explicitly partition advected energy 20 into or components during snowmelt. An unrepresented interaction in any model is the from ponded meltwater which is prevalent in areas of level topography and reduced snowmelt infiltration due to frozen soil (Harder et al, 2017).…”

Section: "The Major Obstacle To the Development Of An Energy Balance mentioning

confidence: 99%

“…The extended GM2002 proposed here was tested using observations reported in Harder et al (2017); the results are summarized in Table 3. The model slightly overestimated and on 30 March 2015, likely due to the limiting assumptions of the GM2002 model.…”

Section: Performance Of Extended Gm2002mentioning

confidence: 99%

“…performance of the extended GM2002 was evaluated with respect to and observations as reported in (Harder et al, 2017). Snow-cover geometry scaling relationships employed in the model framework (Granger et al, 2002;Shook et al, 1993b), originally based on classifications from coarse resolution or oblique imagery, were re-evaluated with high resolution unmanned aerial vehicle (UAV) imagery.…”

Section: "The Major Obstacle To the Development Of An Energy Balance mentioning

confidence: 99%

“…Thus may enhance sublimation when the upwind surface is dry or condense and enhance melt when the upwind surface is wet (Harder et al, 2017). Any attempt to model advection must quantify the dynamic spatial properties of the snow and snow-free patch distributions, , fractional water coverage of ponded water, and horizontal gradients of temperature and humidity between snow and snow-free surfaces.…”

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confidence: 99%

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A simple model for local scale sensible and latent heat advection contributions to snowmelt

Harder¹,

Pomeroy²,

Helgason³

2018

Preprint

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Abstract. Local-scale advection of energy from warm snow-free surfaces to cold snow-covered surfaces is an important component of the energy balance during snowcover depletion. Unfortunately, this process is difficult to quantify in onedimensional snowmelt models. This manuscript proposes a simple sensible and latent heat advection model for snowmelt 10 situations that can be readily coupled to one-dimensional energy balance snowmelt models. An existing advection parameterization was coupled to a conceptual frozen soil infiltration surface water retention model to estimate the areal average sensible and latent heat advection contributions to snowmelt. The proposed model compared well with observations of latent and sensible heat advection providing confidence in the process parameterizations and the assumptions applied. Snowcovered area observations from unmanned aerial vehicle imagery were used to update and evaluate the scaling properties of snow patch 15 area distribution and lengths. Model dynamics and snowmelt implications were explored within an idealized modelling experiment, by coupling to a one-dimensional energy balance snowmelt model. Dry, snow-free surfaces were associated with negative latent heat advection fluxes that compensated for positive sensible heat advection fluxes and so limited the net influence of advection on snowmelt. Latent and sensible heat advection fluxes both contributed positive fluxes to snow when snow-free surfaces were wet and enhanced net advection contributions to snowmelt. The increased net advection fluxes from 20 wet surfaces typically develop towards the end of snowmelt and offset decreases in the one-dimensional areal average melt energy that declines with snowcovered area. The new model can be readily incorporated into existing one-dimensional snowmelt hydrology and land surface scheme models and will foster improvements in snowmelt understanding and predictions.

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Potential for Changing Extreme Snowmelt and Rainfall Events in the Mountains of the Western United States

Harpold

Kohler

2017

JGR Atmospheres

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The intensity of mountain precipitation is often modified by snow accumulation and melt, yet rainfall‐based observations are widely used in planning and design. Comparisons of extreme rainfall versus snowmelt intensities are needed because they have different predictability and hazard implications. Regional warming is expected to intensify not only rainfall and snowfall but also slow snowmelt, which could further challenge intensity duration frequency (IDF) techniques. We use observations from 379 mountain sites across the western U.S. to estimate the 10 and 100 year intensity at 1, 2, and 30 day durations for historical snowmelt (SM), precipitation occurring during snow cover (SCP), and precipitation during the snow‐free period (SFP). At 1 day durations, 100 year SCP was greater than SM and SFP at 40% of sites, while SM was larger than SCP and SFP at 39% of sites. At 30 day durations, SM was greater than SCP and SFP at 95% of sites. The continental sites are generally insensitive to increased water input intensity from SCP occurring as rainfall. In contrast, the maritime mountains are relatively insensitive to changes in SM but have the potential for increased water input intensity from greater SCP occurring as rainfall. Standard precipitation intensity data sets accurately estimated the 100 year, 1 day SCP and SM but underestimated SM at 78 continental sites where SM was greater than SCP and SFP. These results confirm that snow processes modify IDF estimates and highlight regional sensitivity to increased winter rainfall and slower snowmelt that may necessitate local adaptation strategies.

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Local‐Scale Advection of Sensible and Latent Heat During Snowmelt

Cited by 36 publications

References 24 publications

Energy balance and snowmelt drivers of a marginal subalpine snowpack

Energy balance and snowmelt drivers of a marginal subalpine snowpack

A simple model for local scale sensible and latent heat advection contributions to snowmelt

Potential for Changing Extreme Snowmelt and Rainfall Events in the Mountains of the Western United States

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