The influence of characteristics of the Azores High on surface climate: a case study for Peninsular Spain

The correlation between the North Atlantic Oscillation (NAO) and climate variables in Europe shows a strong association in the northern and southern regions, but there is a zone in between where the correlations are not statistically significant. This research paper presents evidence suggesting that understanding the impact of NAO can be enhanced by examining its constituent centers of action (COA), namely, the Azores High (AH) and the Icelandic Low (IL). These COA components continuously vary in intensity and position. To investigate their influence on interannual variations of precipitation in Spain, the study estimates monthly values of COA intensity, latitude, and longitude positions using sea level pressure data. The analysis focuses on their impact on Spain’s precipitation and climate patterns. The correlation between NAO and winter precipitation is found to be weak but statistically significant in northern Spain, while it is not significant in the southern part of the country. By separately assessing the correlations with the AH and the IL, the study reveals that the primary factor influencing interannual precipitation variations in both northern and southern Spain is the intensity of the AH pressure. Specifically, when the AH intensity is at its minimum compared to the mean value, Spain experiences above-normal precipitation. Furthermore, when the AH is located west of its mean longitudinal position, Spain receives increased rainfall. Furthermore, this study observed Iberian Peninsula experiencing a decreasing trend in rainfall in Spain and many factors influence this decreasing trend in rainfall over the Iberian Peninsula. This teleconnection’s impact is more pronounced in northern Spain compared to the southern region, likely due to the presence of mountainous topography that obstructs wind flow. In summary, the study suggests that while the correlation between the NAO and climate variables lacks significance in the central zone of Europe, examining the constituent COA, particularly the AH, provides clearer insights into their influence on interannual precipitation variations and climate patterns in different parts of Spain.