Identifying Climatological Regions and Driving Mechanisms of Frontogenesis

Due to their strong temperature gradients, fronts are a focal point of intense precipitation and gustiness related to extratropical cyclones. In addition, sustained condensational heating along trailing cold fronts has been shown to raise background baroclinicity, which can trigger secondary cyclogenesis and, consequentially, cyclone clustering.

To study the driving mechanism, synoptic-scale characteristics, and impacts of fronts throughout their lifecycles, we have developed a front tracking algorithm. A frontal lifecycle is therein defined as a 4-dimensional space-time volume of strong gradients in equivalent potential temperature that is coherent in both time and space.

Based on the climatology of frontal lifecycles, we identify distinct frontogenesis regions in the mid-latitudes. Frontogenesis typically occurs in the lee of meridionally oriented mountain ranges, such as the Rocky Mountains or the Andes, or along western boundary currents, such as the Gulf Stream or the Kuroshio. Fronts forming in these regions travel eastward along the storm tracks over a lifetime of one to two weeks. Such lifecycle characteristics distinguish mid-latitude fronts from stationary or short-lived airmass boundaries in lower latitudes, which are typically classified as fronts by conventional algorithms.

We furthermore associate characteristic dynamic drivers of frontogenesis in the identified frontogenesis regions to lifecycle properties such as duration, strength, and the occurrence of one or multiple secondary cyclogenesis. Thus, investigating how fronts link large-scale atmospheric conditions with downstream storm activity in the Storm Track regions.