Characteristics of low-level temperature inversions, Whitehorse Yukon Territory: 1956--2003
Near-surface air temperature inversions are a common element of northern environments. Seasonal and inter-annual variations of low-level inversion characteristics were examined using 47 years of twice-daily radiosonde data from Whitehorse airport (1956-2003). Nocturnal low-level inversion events occ...
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| Format: | Thesis |
| Language: | English |
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Université d'Ottawa / University of Ottawa
2009
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| Online Access: | https://dx.doi.org/10.20381/ruor-12443 http://www.ruor.uottawa.ca/handle/10393/28207 |
| Summary: | Near-surface air temperature inversions are a common element of northern environments. Seasonal and inter-annual variations of low-level inversion characteristics were examined using 47 years of twice-daily radiosonde data from Whitehorse airport (1956-2003). Nocturnal low-level inversion events occurred throughout the year in 68% of the 0400h PST radiosonde ascents. Afternoon (1600h PST) inversion events, in contrast, were primarily a winter phenomena, limited to 24% of the readings between October and March, and were deepest and strongest during the winter months. Shorter, weaker, lower magnitude inversions appeared progressively more frequently during the 1974-2003 warming at Whitehorse. The impact (1956-2003) of regular low-level inversions on near surface temperatures in the Yukon River Valley is estimated to be an average annual reduction of -3.4°C. That is to say, in the absence of surface-based temperature inversion effects, the mean annual near-surface-temperature for Whitehorse (-0.7°C) would exceed 1°C, a temperature threshold at which permafrost could not be maintained. Overall inversion impact declined by about 1.5°C between 1956-1973 and 1974-2003. |
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