The study of climate from the perspective of atmospheric circulation, with emphasis on the connections between circulation patterns and climatic differences. The common approach is to determine distinct categories of synoptic weather patterns and then to assess statistically the weather conditions associated with these patterns. The term, which refers to synchronous weather systems such as cyclones and anticyclones, originated during the 1940s when military services became concerned with the climatology of weather types and its implications for transportation. While dynamic climatology is often global in scope, synoptic climatology generally deals with hemispheric or local climates.