ASTIS - Arctic Science and Technology Information System

A search of the ASTIS database for "MAGS" has found the following 52 records, which are sorted by first author.

Comparing the performance of the Canadian Land Surface Scheme (CLASS) for two Subarctic terrain types   /   Bellisario, L.M.   Boudreau, L.D.   Verseghy, D.L.   Rouse, W.R.   Blanken, P.D.
(Atmosphere-ocean, v. 38, no. 1, Mar. 2000, p. 181-204, ill., 1 map)
ASTIS record 48877.
Languages: English
Libraries: ACU

The Canadian Land Surface Scheme "CLASS" is tested for two major terrain types found in the northern Hudson bay Lowland. Soil temperature and energy balance measurements for sedge fen wetland and dwarf willow-birch forest near Churchill, Manitoba, are compared with simulations both with and without the new organic soil parametrization that has been developed for CLASS (Letts et all., 2000), for eight datasets spanning six years (1990 through 1995). With the exception of the sensible heat flux at the sedge site, the new version of CLASS with the organic soil parametrization improves the energy budget simulation at each of the research sites. Both the latent (QE) and ground (QG) heat flux were modelled well; however, some modifications were required to simulate the continued evaporation from these sites once the water table receded below the first soil layer. The sensible heat flux (GH) was the least well simulated component of the energy balance in both versions. Temperatures for the top two soil layers were consistently overestimated by the mineral soil parametrization for both terrain types, whereas the organic soil parametrization showed significant improvement. The new water table diagnostic algorithm in the organic soil version satisfactorily estimates the position of the water table, even under a large range of climatic conditions. The inclusion of organic soil parameters in CLASS, and the subsequent improved handling of soil moisture, is a significant contribution to model development, and provides a physically-based capability for simulating northern peatlands within land surface models. (Au)

A, C, E, F, H, J
Atmospheric circulation; Birches; Bogs; Climate change; Energy budgets; Environmental impacts; Evaporation; Forests; Groundwater; Mathematical models; Numeric databases; Peat; Sedges; Shrubs; Soil moisture; Soil temperature; Wetlands; Willows

G0824, G0825
Churchill region, Manitoba; Hudson Bay region, Manitoba; Hudson Bay region, Ontario; James Bay region, Ontario

Collapse of floating ice covers under vertical loads : test data vs. theory   /   Beltaos, S.
(Cold regions science and technology, v. 34, no. 3, May 2002, p. 191-207, ill.)
ASTIS record 51868.
Languages: English
Web: doi:10.1016/S0165-232X(02)00004-6
Libraries: ACU

Various criteria have been advanced to describe and predict the conditions under which a load will break through a floating ice cover. As a rule, the experimental basis for each of these criteria has been limited, and a comprehensive performance evaluation has yet to be carried out. Criteria based on stress, strain, deflection and strain energy are discussed first, in conjunction with the viscoelastic nature of ice and the mode of failure of an ice sheet. Five data sets are then described and utilized to test and compare the performance of failure criteria that have been proposed in the literature. Stress-based criteria, though simple to use, are only useful for very brief loading because they do not account for loading time and history. Strain- and deflection-based criteria are also subject to time and history effects that similarly limit their applicability to short-term loads. On the other hand, strain-energy criteria are found to apply equally well to short- and long-term loads of different histories. This feature is attributed to implicit consideration of time and load-history effects through integration of the deflection-load variation. Safety implications and future research avenues are discussed. (Au)

Bearing capacity; Creep; Elasticity; Fracturing; Ice loads; Ice sheets; Lake ice; Mathematical models; Salinity; Sea ice; Strain; Stress; Testing; Thickness

G0815, G0822
Joseph Lake, Alberta; Resolute Bay, Nunavut

Spatial and temporal variability of Canadian monthly snow depths, 1946-1995   /   Brown, R.D.   Braaten, R.O.
(Atmosphere-ocean, v. 36, no. 1, Mar. 1998, p. 37-54, ill., maps)
ASTIS record 48867.
Languages: English
Libraries: ACU

In 1995 the Atmospheric Environment Service of Canada (AES) made a major effort to digitize paper records of daily and weekly snow depth that were not in the Canadian Digital Archive of Climate Data. This resulted in the extension of the snow depth record back to the late 1940s at many stations, and the filling of missing data from a number of stations, particularly in the Arctic. This paper describes the database, the methods used both for quality control and to reconstruct missing data, and presents an analysis of the spatial and temporal characteristics of the data over the 1946-1995 period. Principal component analysis of monthly snow depths revealed that snow depths varied coherently over relatively large regions of Canada, with dominant centres of action located over the West Coast, Prairie, Yukon-Mackenzie, southern Ontario, northern Québec and Maritime regions. In many cases, nodes of coherent snow depth variations were associated with corresponding nodes of coherent snow cover duration fluctuations, with the two time series exhibiting significant positive correlations. Winter and early spring snow depths were observed to have decreased significantly over much of Canada in the 1946-1995 period, with the greatest decreases occurring in February and March. These depth decreases have been accompanied by significant decreases in spring and summer snow cover duration over most of western Canada and the Arctic. The snow depth changes were characterized by a rather abrupt transition to lower snow depths in the mid-1970s that coincided with a well-documented shift in atmospheric circulation in the Pacific-North America sector of the Northern Hemisphere. (Au)

F, E, V
Atmospheric circulation; History; Mathematical models; Numeric databases; Ocean-atmosphere interaction; Quality assurance; Snow cover; Snowfall; Spatial distribution; Temporal variations

G08, G0822, G0823, G0824, G0821, G0825, G0826, G0827, G081
Atlantic Provinces; British Columbia; Canadian Arctic; Edmonton, Alberta; Gander, Newfoundland; Nouveau-Québec; Ontario; Prairie Provinces; Whitehorse, Yukon

Thermal features of the Mackenzie basin from NOAA AVHRR observations for summer 1994   /   Bussières, N.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 233-244, ill., maps)
ASTIS record 51879.
Languages: English
Web: doi:10.3137/ao.400210
Libraries: ACU

A series of mid-afternoon Advanced Very High Resolution Radiometer (AVHRR) thermal radiance scenes were assembled in order to develop a better understanding of the complex energy and water processes leading to variations in surface temperature. An in-depth knowledge of the temperature variability is of interest to land surface process modelling and its application to the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS). Clear-sky land surface temperatures are estimated by applying a split window technique to remove atmospheric effects. A maximum land surface temperature map of the Mackenzie basin at 1-km scale for summer 1994 is produced. The patterns are related to land surface features and elevation. The basin's maximum land surface temperature patterns can be subdivided into three land zones (>=35°C, 33-34°C and 27-32°C) and a water dominated zone (20.5°C on average). The highest maximum temperature zone (>=35°C) corresponds to a combination of minimal vegetation, drier soils and low terrain. This zone is not in the southern part of the basin as might be speculated in the absence of these data, but in a wide low elevation corridor from west of Great Bear Lake along the Mackenzie River down to 50°N, 120°W. The maximum land surface temperatures tend to decrease with increasing vegetation density and surface moisture; they also decrease with elevation at a rate of -4.5°C/km. This is confirmed by weather station data. The AVHRR data extend this relationship to the 1200 - 2200 m altitude ranges, where there are no station data. The data suggest that elevation and land cover should be taken into account in the objective analysis (spatial interpolation) of station data. (Au)

E, A, H, F
Atmospheric temperature; Classification; Clouds; Conifers; Energy budgets; Geography; Instruments; Lakes; Land; Mapping; Mathematical models; Measurement; Plant cover; Remote sensing; Satellites; Snow; Solar radiation; Spatial distribution; Surface properties; Temperature; Temporal variations; Thermal properties; Wetlands

G0812, G0821, G0822, G0823
Alberta; Athabasca, Lake, Alberta/Saskatchewan; Athabasca, Lake, region, Alberta/Saskatchewan; British Columbia; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; Saskatchewan

On the physical processes associated with the water budget and discharge of the Mackenzie basin during the 1994/95 water year   /   Cao, Z.   Wang, M.   Proctor, B.A.   Strong, G.S.   Stewart, R.E.   Ritchie, H.   Burford, J.E.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 125-143, ill., maps)
ASTIS record 51873.
Languages: English
Web: doi:10.3137/ao.400204
Libraries: ACU

The Mackenzie River basin water budget and its discharge are investigated using the Canadian Meteorological Centre's Regional Finite Element/Global Environmental Multiscale (RFE/GEM) model-based analyses and observations. A comprehensive water budget analysis for the Mackenzie basin illustrates that the annual convergence of moisture flux over the region is positive, and that the moisture available for precipitation originates mainly from moisture transport across the south-west and north-west boundaries of the basin. In the summer, however, the basin's moisture supply comes mainly from local evaporation. It is found that major atmospheric forcings for discharge are predominantly determined by 1) the nature of the circulation systems and the availability of moisture, and 2) the alteration of moisture gradients through horizontal twisting by the wind fields. The second process is dominant over most of the 1994/95 water year. The basin scale discharge in the autumn (spring) is, to a large extent, related to cyclonic (anticyclonic) circulation systems through moisture redistribution. This occurs due to the horizontal twisting of moisture gradients by the wind fields and the corresponding moisture advection with horizontally-twisted moisture gradients. Over the southern Beaufort Sea, the overall storm frequency in the 1994/95 water year was very low compared with its climatology (Hudak and Young, this issue). However, this region was subjected to the highest percentage of Pacific-origin storms on record during the 1994/95 water year. Synoptic scale weather systems associated with major snowfall and critical spring snowmelt events in the 1994/1995 water year are also examined. Results show that one particular storm in the autumn of 1994 produced much of the initial snowfall for the basin and it was associated with a deep low pressure system providing a great deal of moisture flux into the basin through its western boundaries. It is also shown that a rapid spring snowmelt event in April 1995 was associated with a shallow high pressure system. The descending motion associated with this high pressure system and strong horizontal advection induced by a south-easterly low-level jet were two major elements that contributed to the rapid heating of the basin surface and the subsequent rapid melting of the snow. This unusual snowmelt event was a contributing factor to the annual discharge peak being earlier than normal. (Au)

F, E, D
Albedo; Atmospheric circulation; Atmospheric humidity; Atmospheric pressure; Climate change; Energy budgets; Evaporation; Hydrology; Mass balance; Mathematical models; Precipitation (Meteorology); River discharges; Runoff; Satellite photography; Snow; Snowmelt; Storms; Synoptic climatology; Winds

G0812, G03, G07
Arctic Ocean; Arctic Red River, N.W.T.; Athabasca, Lake, Alberta/Saskatchewan; Canadian Beaufort Sea; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; Peace River, Alberta/British Columbia; Peel River, N.W.T./Yukon

Hillslope hydrology and runoff processes in a Subarctic, subalpine environment   /   Carey, S.K.   Woo, M.-k. [Supervisor]
Hamilton, Ont. : McMaster University, 2000.
xvi, 206 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ72323)
ISBN 0-612-72323-2
Thesis (Ph.D.) - McMaster University, Hamilton, Ont., 2000.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
ASTIS record 54958.
Languages: English
Libraries: OONL

Within the subalpine zone of a subarctic basin, hydrological processes were studied on four hillslopes within 5 km² in an attempt to determine the factors that cause the variability in the magnitude and timing of water balance components. The hillslope was chosen as the scale of study as it links process operating at the point with streamflow, and exhibits strong contrasts in microclimate, vegetation, frost and soils, providing an ideal natural laboratory. Hillslopes showed strong asymmetry in the timing and magnitude of processes during the melt and summer period. On slopes with well drained soils and seasonal frost, vertical hydrological exchanges predominate over the entire year and slopes rarely contribute runoff for streamflow. In contrast, hillslopes underlain with permafrost and/or poorly drained soils with a capping organic layer produce strong lateral fluxes. Water balance information highlighted the principal factors that lead to differences in process magnitudes and timing. This information is important in understanding basin hydrology, as streamflow is a summation of lateral fluxes from slopes. The presence of ice-rich layers blocking soil interstices encourages runoff by restricting drainage. Runoff exhibits a two-layer flow system consisting of quickflow (pathways in the porous organic layer, pipes, rills, and interconnected depressions) and slowflow (pathways in underlying mineral soils and highly decomposed and compacted peat). Quickflow controls the shape and timing of the runoff hydrograph, which is influenced by properties of hillslope wetness and organic layer thickness. Recession analysis revealed variable source areas for runoff generation and highlighted the role of wetness-controlled hydrologic connectivity of a slope segment. Results from this thesis have implications for water resource inventories and predicting hydrologic behaviour of subarctic, subalpine hillslopes. (Au)

F, E, A, C, H
Ablation; Active layer; Aspect; Atmospheric temperature; Drainage; Evaporation; Flow; Frozen ground; Ground ice; Groundwater; Hydrology; Icings; Measurement; Melting; Moisture transfer; Movement; Permafrost; Plants (Biology); Rain; Rivers; Runoff; Seasonal variations; Slopes; Snow; Snow cover; Snow water equivalent; Snowmelt; Soil moisture; Soil percolation; Soil temperature; Solar radiation; Spatial distribution; Stream flow; Thawing; Theses; Thickness; Topography; Trees; Winds

Wolf Creek (60 37 15 N, 134 54 45 W) region, Yukon

The role of soil pipes as a slope runoff mechanism, Subarctic Yukon, Canada   /   Carey, S.K.   Woo, M.-K.
(Journal of hydrology (Amsterdam), v.233, no. 1-4, 12 June 2000, p. 206-222, ill., map)
ASTIS record 61359.
Languages: English
Web: doi:10.1016/S0022-1694(00)00234-1

Pipeflow in subarctic slopes provides a preferential runoff mechanism that bypasses the soil matrix, rapidly conveying water to the stream. Extensive soil piping occurs in the central Wolf Creek basin, Yukon, at the interface of the organic and mineral horizons. Flow in these pipes are ephemeral, transmitting water only when the water table is within or above the zone where pipes occur. During snowmelt, pipeflow began several days after the onset of surface runoff. Pipeflow contribution increased until ground thaw lowered the water tables, leaving matrix flow within the organic layer as the dominant mode of runoff. Pipeflow accounted for 21% of runoff during the 15 day melt period of 1997. Following melt, pipeflow recurred only during two intense summer rainstorms, each yielding different pipeflow response characteristics. During melt, pipeflow closely followed the daily snowmelt cycles and responded earlier than the integrated slope runoff. In the summer, pipeflow hydrographs rose and fell much quicker than direct storm runoff from the entire slope, which was dominated by fast matrix flow within the organic layer. Pipeflow contributing areas were relatively small, but their extent changed with hillslope wetness. Analysis revealed that the Manning flow formula can be combined with contributing areas to simulate pipeflow discharges. Unlike temperate environments where frozen ground is not a factor, the frost table position significantly controls the position of the phreatic surface, and must be considered in any models of pipeflow in permafrost slopes. (Au)

F, C, A, E, H
Aspect; Density; Drainage; Effects monitoring; Frozen ground; Groundwater; Hydrology; Mathematical models; Measurement; Meteorology; Peat; Permafrost; Plant cover; Precipitation (Meteorology); Runoff; Slopes; Snow; Snowmelt; Soil moisture; Soil temperature; Soil texture; Soils; Storms; Temporal variations; Thawing; Weather stations

Whitehorse region, Yukon; Wolf Creek (60 37 15 N, 134 54 45 W) region, Yukon

The role of blowing snow in the hydrometeorology of the Mackenzie River basin   /   Déry, S.J.   Yau, M.R. [Supervisor]
Montreal : McGill University, 2001.
xxi, 190 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ70002)
ISBN 0-612-70002-X
Thesis (Ph.D.) - McGill University, Montreal, Quebec, 2001.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
French résumé provided.
ASTIS record 55242.
Languages: English
Libraries: OONL

Despite being ubiquitous in the Mackenzie River Basin (MRB) of Canada, the role of snow in its energy and water budgets are still open to much speculation. This thesis presents a multi-scale analysis of the contribution of blowing snow to the hydrometeorology of the MRB. A climatology of adverse wintertime weather events is first presented and demonstrates that blowing snow events are rare within the forested sections of the MRB but become more frequent in the northern parts of the basin covered by Arctic tundra. It is these areas which experience the largest impacts of blowing snow transport and sublimation due to large-scale processes. To further assess the mesoscale and microscale effects of blowing snow to the northern regions of the MRB, the development of a bulk blowing snow model is then described. The single- and double-moment versions of the PIEKTUK blowing snow model are shown to produce equivalent results as a previous spectral version of the numerical model while operating about 100 times faster. The application of the double-moment PIEKTUK model (PIEKTUK-D) to a Canadian Arctic tundra site near the northern tip of the MRB reveals that blowing snow sublimation depletes ~3 mm snow water equivalent (swe) from the snowpack over a period of 210 days during the winter of 1996/1997 at Trail Valley Creek, Northwest Territories. Various assumptions on the state of the background thermodynamic profiles and their evolution during blowing snow, however, can yield significantly higher (>300%) rates of sublimation over the same period. PIEKTUK-D is then coupled to the Mesoscale Compressible Community (MC2) model for an interactive simulation of a ground blizzard at Trail Valley Creek. This coupled mesoscale simulation reveals that moistening and cooling of near-surface air associated with blowing snow sublimation is observed but mitigated in part by advective and entrainment processes. Combined, blowing snow sublimation and mass divergence are then shown to remove 1.4 mm swe per day during the Arctic ground blizzard at Trail Valley Creek. Nevertheless, blowing snow contributes to a lesser degree to the surface mass balance of the entire MRB by eroding 0.05 to 0.1 mm swe per year from the snowpack. (Au)

F, E
Atmospheric circulation; Atmospheric humidity; Atmospheric pressure; Atmospheric temperature; Blowing snow; Boundary layers; Energy budgets; Hydrology; Logistics; Mass balance; Mathematical models; Movement; Precipitation (Meteorology); Snow; Snow cover; Snow hydrology; Snow water equivalent; Snowdrifts; Snowfall; Snowstorms; Spatial distribution; Sublimation; Temporal variations; Thermodynamics; Theses; Thickness; Velocity; Visibility; Wind chill; Winds

G0812, G0811, G081, G02, G15
Antarctic regions; Arctic regions; Canadian Arctic; Mackenzie River region, N.W.T.; N.W.T.; Trail Valley Creek region, N.W.T.; Tuktoyaktuk Peninsula, N.W.T.; Yukon

Simulation of an Arctic ground blizzard using a coupled blowing snow-atmosphere model   /   Déry, S.J.   Yau, M.K.
(Journal of hydrometeorology, v. 2, no. 6, Dec. 2001, p. 579-598, ill., maps)
ASTIS record 60283.
Languages: English
Web: doi:10.1175/1525-7541(2001)002<0579:SOAAGB>2.0.CO;2
Libraries: ACU

A ground blizzard occurred from 16 to 18 November 1996 in the northern sectors of the Mackenzie River basin of Canada and the adjacent Beaufort Sea. This hazardous event, accompanied by a low-level jet with wind speeds approaching 20 m/s and extensive blowing snow near the surface (but clear sky aloft), is forced by a strong sea level pressure gradient that forms between a rapidly intensifying anticyclone over the Nunavut and Northwest Territories of Canada and an intense depression over the frozen Arctic Ocean. The event is first simulated at a horizontal grid size of 18 km using the uncoupled Canadian Mesoscale Compressible Community (MC2) model. This experiment is shown to capture the rapid anticyclogenesis event within 2 hPa of its central sea level pressure and the blizzard conditions near the Canadian Arctic coastline and the Beaufort Sea. Meteorological conditions observed at Trail Valley Creek (TVC), a small Arctic tundra watershed in which ground blizzard conditions were experienced during the event, are also accurately reproduced by the uncoupled simulation with the notable exception of the blowing snow process. Thus, the mesoscale model is then coupled to the "PIEKTUK" blowing snow model, and a second simulation is conducted. This additional experiment reveals the presence of extensive blowing snow associated with a strong low-level jet over TVC and the adjacent frozen Beaufort Sea. Over the 2-day event, blowing snow sublimation and transport combined to erode 1.6 mm snow water equivalent from the surface mass balance of TVC. The concurrent moistening and cooling of near-surface air due to blowing snow sublimation emerge during the blizzard but to a lesser extent than in an idealized modeling framework, as a consequence of entrainment and advective processes. Therefore, blowing snow sublimation rates are evaluated to be 1.8 times larger than in the stand-alone application of the PIEKTUK model to the same data. (Au)

F, E, J, L, G
Airplanes; Atmospheric humidity; Atmospheric temperature; Blowing snow; Climate change; Effects of ice on climate; Energy budgets; Environmental impacts; Heat transmission; Hydrology; Mass balance; Mathematical models; Meteorology; Sea ice; Sedimentation; Snow cover; Snow hydrology; Snow water equivalent; Snowfall; Snowstorms; Sublimation; Tundra ecology; Visibility; Winds

Inuvialuit Settlement Region, N.W.T./Yukon; Mackenzie River region, N.W.T.; Trail Valley Creek region, N.W.T.; Tuktoyaktuk Peninsula, N.W.T.

Radiation balance of wetland tundra at northern treeline estimated from remotely sensed data   /   Duguay, C.R.   Rouse, W.R.   Lafleur, P.M.   Boudreau, L.D.
(Climate research, v. 13, no. 1, Sept. 7, 1999, p. 77-90, ill., maps)
ASTIS record 61362.
Languages: English
Web: doi:10.3354/cr013077

Traditional methods of measuring surface net radiation involve point measurements that represent only a small area surrounding the instrumented sites. Remotely sensed spaceborne data offer the means by which to obtain estimates of the outgoing fluxes at the regional scale. The objective of this study was to estimate surface albedo, surface thermal exitance, and net radiation using Landsat Thematic Mapper (TM) data over wetland tundra at northern treeline near Churchill, Manitoba, Canada. Ground-based measurements of each component of the radiation balance were acquired at 5 locations coincident with 2 TM overpasses during summer 1991. Each location was representative of 1 of the major terrain types found in the Hudson Bay Lowlands (i.e. sedge-dominated wetland, upland lichen-heath, tundra lakes and ponds, willow/birch wetland, and open spruce-tamarack forest). The mean absolute differences between remote sensing estimates and field measurements (all sites combined) are 0.01 for albedo, 25.7 W/m² for thermal exitance, and 14.1 W/m² for net radiation. The 2 summer 1991 TM Images (June and August) were then used to examine within and between terrain type variations in surface net radiation during the growing season. TM Imagery from August 1984 and August 1991 were also utilized to investigate differences in surface fluxes between a dry year (1984) and a wet year (1991). Results indicate that surface wetness and, to a lesser extent, phenology are the 2 main factors controlling the radiation balance during the summer period in this subarctic tundra-forest landscape. (Au)

E, F, A, C, H, J
Albedo; Birches; Conifers; Energy budgets; Evaporation; Groundwater; Growing season; Hydrology; Instruments; Mapping; Measurement; Meteorological instruments; Plant cover; Plant-water relationships; Plants (Biology); Precipitation (Meteorology); Remote sensing; Satellites; Seasonal variations; Sedges; Soil moisture; Solar radiation; Surface properties; Taiga ecology; Temperature; Temporal variations; Thermal properties; Treeline; Tundra ecology; Tundra ponds; Weather stations; Wetlands; Willows

Churchill region, Manitoba; Hudson Bay region, Manitoba

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