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University of New Mexico (2016)

Effects of the ground heat flux on snowpack ablation in a semi-arid mountain climate

Mickschl, Chad

Titre : Effects of the ground heat flux on snowpack ablation in a semi-arid mountain climate

Auteur : Mickschl, Chad

Université de soutenance : University of New Mexico

Grade : Master of Water Resources 2016

Résumé
In anticipation of warmer temperatures, receding snowlines, and increasing water demands, it will be important for water managers to understand how changes in snowpack depth and distribution will affect available runoff. Mountain snowpacks make up the largest component of runoff in mountain regions generating water supply for a host of downstream users. As climate warming persists, mountainous areas with traditionally deeper snowpacks will shift towards a shallower, more transitional regime. Transitional lower elevation snowpacks will begin to experience an increasing number of melt-off and ripening periods throughout the course of a winter. To better predict changes in water resources, it is necessary to gain a more detailed knowledge of the snowmelt energy balance of shallow snow as well as quantification of lower elevation snowline energy fluxes. Typically, the ground heat flux (G) is assumed to be very small compared to other energy fluxes incident the snowpack. To understand snowpack processes, this research aims to (1) assess the contribution of the ground heat flux in the Jemez Mountains compared to other mountain regions using the SNOBAL model, (2) compare calculated and modeled ground heat flux values, and (3) determine if near surface ground temperatures can be used as an indicator of snowpack ripening and presence. To capture the energy fluxes of the snowpack, two weather stations were deployed within the Alamo Creek Watershed on a north aspect at 9800ft and a south aspect at 8600ft. To capture and quantify the energy fluxes beneath the snowpack, near surface soil temperatures were recorded for the duration of the snow-covered season with HOBO temperature sensors. The data recorded by these temperature sensors were used to calculate the ground heat flux as well as determine snowpack ripening and day of melt. Near surface ground temperatures at 2cm were above 0\u2103 during the duration of the snow covered season. G fluxes increased slightly as snowpack depth increased and more significantly during snow depths less than 25cm towards the end of the snow covered season. Seasonal ground heat flux accounted for 26% of the snowpack ablation. Snowpack modeling with typically assumed 0\u2103 ground temperatures resulted in snowpacks that did not melt by the observed melt date indicating that the G flux is more significant in this semi-arid mountain region. Near surface soil temperatures allowed the determination of snowpack presence and disappearance, however the ripening dates were less certain.

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Page publiée le 28 octobre 2016, mise à jour le 17 octobre 2019