Abstract
Abstract. The atmospheric circulation clearly has an important influence on variations in surface temperature and precipitation. In this study we illustrate the spatial patterns of variation that occur for the principal circulation patterns across Europe in the standard four seasons. We use an existing classification scheme of surface pressure patterns, with the aim of considering whether the patterns of influence of specific weather types have changed over the course of the 20th century. We consider whether the long-term warming across Europe is associated with more favourable weather types or related to warming within some of the weather types. The results indicate that the latter is occurring, but not all circulation types show warming. The study also illustrates that certain circulation types can lead to marked differences in temperature and/or precipitation for relatively closely positioned sites when the sites are located in areas of high relief or near coasts.
Highlights
The influence of the circulation on surface climate has been known by humans since the beginning of time
Since the advent of climatology these relationships have developed into circulation or weather types developed initially subjectively (e.g. Lamb, 1972 for the British Isles and Hess and Brezowsky, 1977 for Europe – the well know “Grosswetterlagen”) but objectively with a wide range of approaches and techniques
The second study looked at temperatures at De Bilt in the Netherlands and assessed whether 20th century temperature increases were specific to certain wind directions
Summary
The influence of the circulation on surface climate has been known by humans since the beginning of time. Beck et al (2007) consider similar aspects, but only use monthly resolution data We extend these studies to the European scale and use continental-scale circulation typing approaches. Philipp et al (2007) have developed a set of daily North Atlantic/European Circulation Types (CTs) covering the region 70◦ to 25◦ N by 70◦ W to 50◦ E using a technique involving simulated annealing (a clustering algorithm). The NAO (based for example on the normalized pressure difference between Gibraltar and Reykjavik) explains up to 40% of the variance of winter season (December to February) temperature variability in southern Scandinavia (Jones et al, 2003), yet if a more local pressure gradient were developed (for this location using, for example, pressure data from Berlin and Stockholm) the explained variance would be considerably higher. The locations of the available data used for the illustrated influences of each CT on surface climate will be evident in the subsequent figures
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