Spatiotemporal Changes in Frost Indicators in Southeastern Spain (1950–2020): Influence of the East Atlantic Index (EA).

The southeastern interior of the Iberian Peninsula (Spain) is characterized by a complex orography, which determines a pronounced altitudinal gradient, significant slopes, and marked valleys with important temperature inversion processes. In this work, to analyze the yearly and seasonal evolution of minimum temperatures, six indicators related to minimum temperatures were used: the frost days (FD) and number of days with minimum temperature below −2°C (TNltm2), 10th temperature minimum percentile (TN10p), absolute minimum temperatures (TNn), average minimum temperatures (TNm), and cold-spell duration index (CSDI). For this, the Spearman nonparametric statistical test was used to analyze data from a total of 22 meteorological stations (1950–2020), using a daily resolution of minimum temperatures. Significant changes during the study period were revealed, especially between the 1960s and 1990s. In most cases, there has been a statistically significant increase in the minimum temperatures in the study area, except in the western (most mountainous) part, where the dynamics differed from the rest of the interior of the southeast of the peninsula. Nine large global teleconnection patterns were analyzed in relation to the average minimum temperatures in the study area. These are well-characterized indices for the Northern Hemisphere, which show a very high correlation of the average minimum temperatures with the temporal evolution of the global climate pattern of the east Atlantic (EA) index, especially in the Mediterranean region of the Iberian Peninsula, where it seems to have a very marked influence. Significance Statement: We analyzed variation in observed minimum temperatures during 1950–2020 in inland southeastern Spain. Temporal analysis of "east Atlantic index" cycles and their interrelation with frost days and minimum temperatures is very relevant for seasonal meteorological prediction in the study area, where agroindustry represents 20% of GDP. The results show a significant decrease in frost days and an increase in average minimum temperature, especially in coastal and prelittoral areas. The variations are less important mountainous western areas, where frost days have even increased. This is explained by a change in the atmospheric dynamics in midlatitudes of the Atlantic Ocean, quantified by the east Atlantic global teleconnection index, which has a high statistical correlation with Spanish minimum temperatures, especially in winter. [ABSTRACT FROM AUTHOR]