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Philip Marsh and John R. Gyakum
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Ming-Ko Woo and Philip Marsh

Abstract

Water balance studies in tundra regions require accurate snowfall data but weather station records often underestimate basin snow storage. However, snow storage can be determined by snow surveys conducted prior to the melt period because Arctic snowpacks do not melt during winter. Topography strongly controls snow distribution. A basin can be subdivided into various terrain types and the snow survey then establishes the snow characteristics of each terrain type so that basin snow storage is obtained as their areally weighted mean.

Such a survey was carried out in small basins near Resolute, Northwest Territories, traversing different types of terrain. The results confirmed that weather station snowfall grossly underestimated basin snow storage. Since it is also desirable to simplify future snow surveys by reducing the number of transects, an error analysis was performed to determine the error resulting from a grouping of terrain types. It was found that both maximum and mean error increased as the number of terrain types was reduced, but the increase was not substantial when certain terrain types were combined. A mean error of 15% is expected when only four types of terrain (hilltops, flats, gullies-valleys and slopes) are recognized in the survey, but the error quickly increases when further simplification of the terrain is introduced.

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Philip Marsh, Wayne R. Rouse, and Ming-ko Woo

Abstract

Recent studies have demonstrated empirical relationships between surface soil moisture and the α′ parameter in Priestley and Taylor's version of the combination model. An evaporation study conducted at a high arctic site shows that for gravel and loamy surfaces underlain by permafrost, α′ can be expressed as the following function of soil moisture (S m):

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Comparison with α′ and soil moisture relationships obtained in more temperate latitudes suggests that under drying conditions the evaporation rate will be a response to the particular site characteristics, so that there is no unique relationship between surface soil moisture and evaporation rates.

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Andrea K. Eaton, Wayne R. Rouse, Peter M. Lafleur, Philip Marsh, and Peter D. Blanken

Abstract

In this study, the surface energy balance of 10 sites in the western and central Canadian subarctic is examined. Each research site is classified into one of five terrain types (lake, wetland, shrub tundra, upland tundra, and coniferous forest) using dominant vegetation type as an indicator of surface cover. Variations in the mean summertime values (15 June–25 August) of the energy balance partitioning, Bowen ratio (β), Priestley–Taylor alpha (α), and surface saturation deficit (D o) are compared within and among terrain types. A clear correspondence between the energy balance characteristics and terrain type is found. In addition, an evaporative continuum from relatively wet to relatively dry is observed among terrain types. The shallow lake and wetland sites are relatively wet with high Q E/Q* (latent heat flux/net radiation), high α, low β, and low D o values. In contrast, the upland tundra and forest sites are relatively dry with low Q E/Q*, low α, high β, and high D o values.

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Wayne R. Rouse, Andrea K. Eaton, Richard M. Petrone, L. Dale Boudreau, Philip Marsh, and Timothy J. Griffis

Abstract

This study details seasonal characteristics in the annual surface energy balance of upland and lowland tundra during the 1998–99 water year (Y2). It contrasts the results with the 1997–98 water year (Y1) and relates the findings to the climatic normals for the lower Mackenzie River basin region. Both years were much warmer than the long-term average, with Y1 being both warmer and wetter than Y2. Six seasons are defined as early winter, midwinter, late winter, spring, summer, and fall. The most rapid changes in the surface energy balance occur in spring, fall, and late winter. Of these, spring is the most dynamic, and there is distinct asymmetry between rates of change in spring and those in fall. Rates of change of potential insolation (extraterrestrial solar radiation) in late winter, spring, and fall are within 10% of one another, being highest in late winter and smallest in spring. Rates of change in air temperature and ground temperature are twice as large in spring as in fall and late winter, when they are about the same. Rates of change in components of the energy balance in spring are twice and 4 times as large as in fall and late winter, respectively. The timing of snowpack ripening and snowmelt is the major agent determining the magnitude of asymmetry between fall and spring. This timing is a result of interaction between the solar cycle, air temperature, and snowpack longevity. Based on evidence from this study, potential surface responses to a 1°C increase in air temperature are small to moderate in most seasons, but are large in spring when increases range from 7% to 10% of average surface energy fluxes.

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