Climatology and historical snowcover of the Big Level Plateau, Gros Morne National Park, Newfoundland

Martin, Christian (2004) Climatology and historical snowcover of the Big Level Plateau, Gros Morne National Park, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The daily climatological record including snowcover water equivalent (SWE) was estimated for the Big Level Summit Plateau (BL), Gros Morne National Park, western Newfoundland, for the 1962-1999 study period. This was accomplished using widely known statistical techniques, i.e. multiple linear regression and mean ratios, linking the Big Level Autostation (1993-1999) record with the nearby low lying coastal stations records through the climate elements mentioned above. Physically based relationships were added for the snow model, which was based on the reconstructed climatological elements (temperature, wind speed and precipitation). -- The BL daily temperature record (estimated for 1946-1999) and hourly wind speed record were estimated with multiple linear regression. Precipitation was estimated using mean ratios. The estimated BL winter precipitation record was separated into snowfall and rainfall and measured snowfall at BL was corrected for wind induced undercatch. Snowcover SWE was estimated with the estimated daily precipitation record and the temperature index method, using increasing degree-day factors as the snow season progressed. Snowdrifting off the plateau and sublimation of blowing snow were also estimated using simple expressions that were a function of wind speed. -- Snowcover on BL is consistently present for long periods from year to year, although its thickness varies considerably compared with the coastal plain (BL maximum seasonal SWE varied from 110 mm to 1650 mm). The single largest factor influencing the snowcover SWE, other than the large amounts of snowfall, was found to be blowing snow sublimation, which ablates approximately 53% of the snowfall accumulation on average. Another large factor influencing snowcover SWE is snowdrifting off the plateau, accounting for approximately 10% of the average accumulated snowfall, leaving approximately 32% to be ablated by melt. The months from February to June all showed negative significant trends with respect to mean BL SWE during the study period. There were no significant linear trends in the temperature record for the period of estimation, but there was a significant linear positive trend (95% level) for the number of thawing degree-days using daily maximum temperature for the snow accumulation season (November-April) of 1.3-1.8 degree-days per year. -- An anthropogenically induced warmer climate would lead to much thinner snowcovers existing during shorter periods, with snow seasons having reduced snowfall and increased rainfall values. The thinnest seasonal snowcovers of the recent past such as in the 1981 snow season could become above average if the IPCC climate change projections become reality.

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