Transient anticyclonic eddies and their relationship to atmospheric block persistence

Abstract. Atmospheric blocking is a circulation pattern that describes the presence of large-scale, persistent anticyclones, which have potential to bring severe impacts at surface. However, dynamical behaviour blocks still not fully understood. For example, factors determine persistence events are clear. In this study, relationship between and smaller-scale transient anticyclonic eddies examined, with particular focus on impact transients block. Analysis performed in two areas: Euro-Atlantic North Pacific, locations both high frequency for impacts. Geopotential height anomalies 500 hPa used identify eddies. This allows Eulerian definition blocking, as well Lagrangian perspective It found experience northward acceleration prior entering block, indicative ridge building ahead block but could also potentially provide evidence previously proposed selective absorption mechanism maintenance. A general whereby longer interact more than less all times year. effect strongest winter weakest summer, agrees fact most least summer. strength eddy interacts measured by its maximum geopotential anomaly, has complicated persistence. The determining factor Pacific region. longest stronger shortest seasons except when reverse true. By contrast, only result from autumn winter. We therefore conclude number important persistence, having variable effect.