A summer climate regime over Europe modulated by the North Atlantic Oscillation

Abstract

Abstract. Recent summer heat waves in Europe were found to be preceded by precipitation deficits in winter. Numerical studies suggest that these phenomena are dynamically linked by land-atmosphere interactions. However, there exists as yet no complete observational evidence that connects summer climate variability to winter precipitation and the relevant circulation patterns. In this paper, we investigate the functional responses of summer mean and maximum temperature (June-August, T mean and T max ) as well as soil moisture proxied by the self-calibrating Palmer drought severity index (scPDSI) to preceding winter precipitation (JanuaryMarch, P JFM ) for the period 1901-2005. All the analyzed summer fields show distinctive responses to P JFM over the Mediterranean. We estimate that 10 ∼ 15% of the interannual variability of T max and T mean over the Mediterranean is statistically forced by P JFM . For the scPDSI this amounts to 10 ∼ 25%. Further analysis shows that these responses are highly correlated to the North Atlantic Oscillation (NAO) regime over the Mediterranean. We suggest that NAO modulates European summer temperature by controlling winter precipitation that initializes the moisture states that subsequently interact with temperature. This picture of relations between European summer climate and NAO as well as winter precipitation suggests potential for improved seasonal prediction of summer climate for particular extreme events.

Analysis of extreme summers and prior late winter/spring conditions in central Europe

“…By comparing regional climate simulations of a coupled atmosphereland-surface model scheme to an uncoupled model scheme for selected summer heat waves in Europe, Fischer et al (2007) estimated that land-atmosphere interactions over dry areas increase the number of heat days by 50-80 %. Wang et al (2011) supported the findings of Fischer et al (2007) by analysing observational data of the Mediterranean region. Zampieri and D'Andrea (2009) found that spring droughts in the Mediterranean favor the development of strong heat events in "temperate continental Europe", and Hirschi et al (2011) point out the importance of soil-moisture deficit for the development of strong heat waves in southeastern Europe.…”

“…For example Hirschi et al (2011) found that drier surface conditions lead to an intensification of hot extremes in southeastern Europe; Barriopedro et al (2011) came to similar conclusions for the hot summer of 2010 in western Russia, and Wang et al (2011) found similar relationships in the Mediterranean. A first attempt to check if the results are valid for a larger area is made, by applying the methods described to the region 30 • N-70 • N, −20 • E-70 • E (not shown).…”

“…Within this larger area, many different mechanisms apply (different synoptic regimes at a time, different regional phenomena), such that positive and negative anomalies of the variables in question equalize. However, as indicated by other authors, the mechanisms found might be valid for other areas within Europe other than the region under investigation in this study (Fischer et al 2007, Wang et al 2011, Hirschi et al 2011, Zampieri and D'Andrea 2009.…”

Observationally based analysis of land–atmosphere coupling

“…The analysis method is based on the coupled manifold (CM) technique (Navarra and Tribbia, 2005), which was specifically designed to analyse covariation between fields considering both the local and remote forcing of one field to the other. The CM technique has proved to be successful for the analysis of different climate fields, like precipitation, vegetation characteristics, sea surface temperature (SST), and temperature over land (Alessandri and Navarra, 2008;Cherchi et al, 2007;Wang et al, 2011a). Recently, the CM technique has been also applied to investigate the relationship between surface temperature and electricity demand in summer (De Felice et al, 2014).…”

The influence of large-scale climatic patterns on precipitation, temperature, and discharge in Czech river basins

“…The climate over Europe is related mainly to the North Atlantic sector, which is ordinarily captured by the North Atlantic Oscillation (NAO) (Hurrell, 1995). Thorough research has been conducted relating the NAO to temperatures (Pozo-Vázquez et al, 2001;Wang et al, 2011), precipitation (Uvo, 2003;Bartolini et al, 2009) or directly to discharges (Shorthouse and Arnell, 1999;Rimbu et al, 2002). Pekárová and Pekár (2007) recently investigated teleconnections of streamflow fluctuations in Slovakia with Quasi-Biennial Oscillation (QBO), Southern Oscillation (SO), NAO, and Arctic Oscillation (AO).…”