Frontal impacts on carbon dioxide concentrations at a forested site in the Virginia Blue Ridge Mountains

Mountains have long been known to impact frontal structure and associated mesoscale dynamics. Frontal interactions with the Rocky Mountains and European Alps have been well-studied because of a dense network of monitoring stations. However, such a network does not exist within the Appalachian Mountains. Thus, studies of frontal impacts with the Appalachians have been limited to large-scale climatological and modeling studies, which have shown that the Appalachians have a significant influence on fronts. The strength of this impact is unclear and is important to understanding how passive tracers, such as carbon dioxide, are transported.

To help describe how fronts are affected by the Appalachian Mountains, we will use meteorological data, as well as measurements of carbon dioxide concentration, collected from a mountaintop site in the Virginia Blue Ridge Mountains, located along the eastern flank of the Appalachians. Cold fronts will be identified during a 1-year period between 1 September 2008 and 31 August 2009 using two different criteria: 1) temporal changes in in-situ meteorological observations of temperature and pressure, and 2) spatial changes in 850mb equivalent potential temperature gradients using the North American Regional Reanalyses (NARR). Using these criteria, the number of identified cold front passages was 36 and 37, respectively.

The interaction of fronts with the Appalachian Mountains may affect the carbon dioxide concentration footprint of the mountaintop location, which we will seek to understand using a backward trajectory model (the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model) and a NOAA-derived global carbon-tracking model (CarbonTracker). By using these models, we show that we can improve our understanding of transport and mixing processes associated with frontal passages in mountains and their effect on the observed carbon dioxide concentrations on mountaintop locations.