A Climatology of Lower Stratospheric Fronts in North America
Using twice daily NCEP/NCAR Global Forecast System (GFS) 1-degree analyses, a synoptic climatology of LSFs was constructed from 184 cases identified during the 2004-05 to 2011-12 winter seasons. LSFs, like their tropospheric counterparts, are characterized by larger than background horizontal potential temperature gradients, cyclonic shear, and static stability. The cases were then divided into their synoptic scale flow environment (northwesterly, westerly, etc.) and composited. These composite analyses revealed that LSFs tend to form in two distinct environments, which led to further analysis of the development of LSFs over (1) the Rocky Mountains and (2) the Eastern United States. The results of this comparative analysis and the proposed mechanisms involved in lower stratospheric frontogenesis and frontolysis will be presented.