Surface Fronts, Troughs, and Baroclinic Zones in the Great Lakes Region

Abstract

Abstract The temporal frequency and spatial distributions of fronts and troughs in the Great Lakes region from a 6-yr period (January 2000–December 2005) are presented. Frontal frequencies indicated that cold fronts were the most common, followed by stationary, warm, and occluded fronts, in that order. The variation in the annual frequency of all front types was small throughout the period. Troughs were present more frequently than any front type and exhibited greater variability of annual frequency. An investigation of the relation of fronts and troughs to surface baroclinic zones found that approximately 54% of analyzed fronts were associated with a moderate potential temperature gradient of at least 3.5°C (100 km)−1. Nearly 10% of all fronts were associated with a strong baroclinic zone having a potential temperature gradient of at least 7.0°C (100 km)−1. Moderate or strong baroclinic zones were associated with about 34% of the analyzed troughs in the Great Lakes region and this relationship was further examined for three different trough classifications (i.e., synoptic, subsynoptic, and mesoscale). This study is one of very few to present the climatological variability of surface fronts of all types across a region and the results provide useful insights into the current operational determination of analyzed surface fronts and troughs by quantifying their association with surface baroclinic zones in the Great Lakes region.