Circulation weather types as a tool in atmospheric, climate, and environmental research

Citation: Ramos AM, Barriopedro D and Dutra E (2015) Circulation weather types as a tool in atmospheric, climate, and environmental research. Classifications of circulation weather systems have a long history in meteorology and climatology. Starting with manual classifications (Hess and Brezowsky, 1952; Lamb, 1972) over specific regions of the globe, these tools (generally called " catalogs of synoptic types ") were restricted mainly to weather forecasting and historical climate studies. In the last decades, the advance of computing resources and the availability of datasets have fostered the development of fast and objective methods that process large amounts of data. Many climatological studies and applications require these data to be as simplified as possible; this is often achieved by analyzing gridded datasets (usually sea level pressure or geopotential height at different levels), and grouping the data into a relatively small number of distinct categories. Since these types are based on meteorological fields observed at a specific instant, they are also called Eulerian classifications. Several classification methods of circulation weather types have been developed, and are currently used in a wide range of applications Sheridan stated that the " Synoptic weather-typing, or the classification of weather conditions or patterns into categories, continues to be popular, and numerous methods have been developed over the past century " (Sheridan, 2002). The increasing interdisciplinary use of circulation weather types in Europe became clear when the European project " Harmonization and Applications of Weather Types Classifications for European Regions—COST733, " where a wide range of classification schemes for different spatial domains were developed and compared within the scope of distinct applications. In recent years, the usefulness of circulation weather type classifications has been demonstrated in a large number of scientific domains from climate (Kysely and Domonkos, 2006; Lorenzo et al., 2011), to environmental areas such as air quality (Demuzere et al., 2009) and forest fires (Kassomenos, 2010) or upwelling activity (Ramos et al., 2013). The relationship between circulation weather type classifications and high-impact weather events was also shown in extreme temperature episodes (Kysely, 2008, floods Prudhomme and Genevier, 2011), droughts (Russo et al., 2015), or even lightning activity (Ramos et al., 2011). Automatic circulation weather type classification algorithms have also allowed exploring the variability of the atmospheric circulation over Europe during the last centuries. This has been possible by using either historical monthly mean grids going back to the eighteenth century (Beck et al., 2007) or …