Overview of Advances in Synoptic Meteorology： Four Stages of Development in Conceptual Models of Frontal Cyclones

The advance of fluid dynamics may be divided into four stages: ancient, classical, neoteric, and contemporary. A similar four-stage framework can be used to describe the advance of synoptic meteorology, such as the conceptual models of extratropical cyclones and their attendant fronts. The first conceptual model of extratropical cyclones was proposed by Admiral FitzRoy in 1863. Based purely on Admiral FitzRoy's personal experience (although it does contain some scientific essentials), this model represents the \ancient stage of synoptic meteorology. The Norwegian cyclone model was developed based on Newtonian mechanics about 100 yr ago, and represents the classical stage of synoptic meteorology. This model was based on the idea that weather changes are primarily caused by baroclinicity, but contain some serious flaws. In particular, the Norwegian model regards fronts as zeroth-order discontinuities in density, which is inconsistent with the continuity principle of fluid dynamics. The Chicago three-dimensional conceptual model of fronts and cyclones, which was developed approximately 50 yr ago by using quasi-geostrophic theory, can be thought of as representing the neoteric stage of synoptic meteorology. The Chicago model was replaced in the late 20th century by a model of extratropical cyclones characterized by back-bent and wrap-up warm fronts. This model has been developed with massive numerical calculations, and represents the contemporary stage of synoptic meteorology. In the era of large data, contemporary synoptic meteorology should be careful to maintain and make full use of the profound physical understanding generated during the neoteric stage of synoptic meteorology.