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  • Thumbnail for Micrometeorology of a Diffuse Tree Line: How do airflow structures affect sensible heat flux divergence and temperature-controlled tree growth?
    Micrometeorology of a Diffuse Tree Line: How do airflow structures affect sensible heat flux divergence and temperature-controlled tree growth? by Sondermann, Dylan P

    Harsch (2009, 2011) determined that diffuse tree lines are advancing globally as a response to warmer growing season temperatures. However, few have studied the local micrometeorological processes that change local climatic conditions for trees. This thesis aims to understand local airflow patterns and heat distribution within a diffuse tree line on Pikes Peak (Teller County, CO). Previous research identified that the study site represents an advancing tree line that has transitioned from an abrupt to a diffuse structure within the last century (Kummel et al. 2009-present). The mountain location of the study site governs large-scale wind patterns as an anabatic-katabatic wind system. On a more local scale, surface interactions at the diffuse tree line alter daytime flows, resulting in the formation of a low level jet. This jet alters climatic conditions by creating three vertical sub-layers with different atmospheric properties. A preliminary heat budget analysis of the diffuse tree line confirms the findings of jet characteristics while also determining that the low level jet is capable of altering vertical heat distribution and depositing heat as flows move uphill. This heat deposition is likely connected to growth patterns studied by Marks (2014) and overall tree line dynamics (Elwood et al. 2012).