No abstract

A relationship between midlatitude cyclone (MLC) tracks and snow-cover extent has been discussed in the literature over the last 50 years but not explicitly analyzed with high-resolution and long-term observations of both. Large-scale modeling studies have hinted that areas near the edge of the snow extent support enhanced baroclinicity because of differences in surface albedo and moisture fluxes. In this study, the relationship between snow-cover extent and midlatitude disturbance (MLD) trajectories is investigated across North America using objectively analyzed midlatitude disturbance trajectories and snow-cover extent from the North American Regional Reanalysis (NARR) for 1979-2010. MLDs include low-level mesoscale disturbances through midlatitude cyclones. A high-resolution MLD database is developed from sea level pressure minima that are tracked through subsequent 3-h time steps, and a simple algorithm is developed that identified the southern edge of the snow-cover extent. A robust enhanced frequency of MLDs in a region 50-350 km south of the snow-cover extent is found. The region of enhanced MLD frequency coincides with the region of maximum low-level baroclinicity. These observations support hypotheses of an internal feedback in which the snow-cover extent is leading the disturbance tracks through surface heat and moisture fluxes. Further, these results aid in the understanding of how midlatitude disturbance tracks may shift in a changing climate in response to snow-cover trends.