No description available.

Thesis (M.Sc.). / Written for the Dept. of Atmospheric and Oceanic Sciences. Title from title page of PDF (viewed 2008/05/13). Includes bibliographical references.

No description available.

Mémoire (M.Sc.A.)--Université du Québec à Chicoutimi, 1984. / Document électronique également accessible en format PDF. CaQCU

The relationship between soil temperature and CO₂ flux from undisturbed soil cores was examined during freeze-up of arctic tundra. Three habitats which dominate tundra topography, polygon trough, ridge and basin, produced significantly different amounts of CO₂ when soil temperatures were above 0 C. A significant positive correlation between soil temperatures between 10 to -7 C and CO₂ flux from each habitat was established. Substantial quantities of CO₂ were produced during freeze-up period when soil temperatures remained near 0 C for an extended period, and the CO₂ production continued at reduced levels as the soil temperature dropped below 0 C. When soil temperatures reached -7 C and the study was terminated, the CO₂ flux was reduced to a low level, but did not reach extinction. A maximum CO₂ flux of 2925 mg CO₂/m²/day from the trough habitat was observed when the soil temperature was 10 C, and the minimum CO₂ flux of 131 mg/m²/day was observed when the soil temperature was -7 C. These data are consistant with the hypothesis that soil microorganisms in arctic tundra are capable of physiological activity in the range of 0 to -7 C. / Master of Science

M. S.

Le suivi et la représentation de la variabilité du manteau neigeux en montagne sont des enjeux écologiques et sociétaux majeurs. Le récent développement de modèles météorologiques à échelle kilométrique offre un potentiel nouveau pour améliorer les simulations d'enneigement en montagne. Dans cette thèse, nous avons évalué l'apport des prévisions météorologiques du modèle de prévision numérique du temps AROME à 2.5 km de résolution horizontale pour alimenter le modèle détaillé de manteau neigeux Crocus. Les simulations AROME-Crocus distribuées ont d'abord été évaluées sur les Pyrénées de 2010 à 2014, montrant un apport en termes de représentation de la variabilité spatio-temporelle du manteau neigeux par rapport à l'approche par massif du système opérationnel actuel SAFRAN-Crocus, malgré une surestimation des hauteurs de neige. Par la suite, la valeur ajoutée de produits satellitaires de rayonnements incidents a été étudiée pour des simulations d'enneigement dans les massifs alpins et pyrénéens, soulignant leur bonne qualité en montagne mais un impact mitigé sur le couvert neigeux simulé. Enfin, on a montré comment le schéma de microphysique nuageuse d'AROME associé à Crocus permet de mieux prévoir la formation de glace en surface du manteau neigeux par précipitations verglaçantes dans les Pyrénées. Ces travaux ouvrent la voie à une prévision nivologique distribuée à haute résolution en montagne. / Monitoring and representing the snowpack variability in mountains are crucial ecological and societal issues. The recent development of meteorological models at kilometric scale offers a new potential to improve snowpack simulations in mountains. In this thesis, we assessed the potential of forecasts from the numerical weather prediction model AROME at 2.5 km horizontal resolution to drive the detailed snowpack model Crocus. AROME-Crocus distributed simulations were first evaluated over the Pyrenees from 2010 to 2014. They showed benefits in representing the snowpack spatio-temporal variability as compared to the massif-based approach of the current operational system SAFRAN-Crocus, despite an overestimation of snow depth. Then, we studied the potential added value of satellite-derived products of incoming radiations for simulating the snow cover in the French Alps and Pyrenees. These products were found of good quality in mountains but their impact on the simulated snow cover is questionable. Finally, we showed how the cloud microphysics scheme of AROME associated with Crocus enables to better predict ice formation on top of the snowpack due to freezing precipitation in the Pyrenees. These works pave the way for high-resolution distributed snowpack forecasting in mountains.