Regional differential behaviour of maximum temperatures in the Iberian Peninsula regarding the Summer NAO in the second half of the twentieth century

V. Favà, J.J. Curto, M.C. Llasat

Abstract

The relationship between atmospheric circulation in northern Europe in summer and the maximum temperatures (Tx) of the Iberian Peninsula (IP) have received little attention. In this article we explore which synoptic structures related to high absolute values of SNAO (Summer North Atlantic Oscillation) are linked to significant anomalies in the maximum temperatures of the IP on a regional scale. Furthermore, we examine how the frequency of these structures has contributed to the differential evolution of maximum temperature trends in the IP and modulated the relationship between the SNAO and the maximum temperatures of the IP in the second half of the twentieth century.

Four basic synoptic structures were identified and their time series were calculated. Thus, we can explain why significant positive correlations between the SNAO and the maximum temperatures for the north of the IP are found for the 1951–1967 period, while in the 1962–1978 period these correlations are negative and affect the eastern part of the IP.

We found that, for the 1951–1967 period, the negative SNAO contributed to a lowering of the maximum temperatures in the NW and north IP and to a strengthening of the north-south IP maximum temperature gradient. During the 1970s and the start of the 1980s, owing to the much higher values of SNAO, the more negative anomalies in the coldest days shifted towards the east of the IP.

Keywords

• Summer NAO;
• Maximum temperatures;
• Regional trends;
• Temperature gradient;
• Pressure gradient;
• Iberian Peninsula

You can download here: http://www.sciencedirect.com/science/article/pii/S0169809516302319