Variability of maximum and minimum monthly mean air temperatures over mainland Spain and their relationship with low-variability atmospheric patterns for period 1916–2015

The analysis of monthly air temperature trends over mainland Spain during 1916–2015 shows that warming has not been constant over time nor generalized among different months; it has not been synchronous for maximum and minimum air temperatures; and it has been heterogeneous in space. Temperature rose during two characteristic pulses separated by a pause around the middle of the 20th century in some months. In other months, only the second rising period is identified, or no warming can be found. In all months, and both for maximum and minimum air temperatures, a stagnation of the increasing trend is observed in the last two decades of the study period. High spatial variability exists in trend signal and significance, and two contrasting temporal patterns of advance over the study area are identified for maximum and minimum air temperatures. These patterns can be related to prevalent flow directions and relief disposition with respect to the flows associated with low-variability meteorological patterns North Atlantic Oscillation (NAO) and Western Mediterranean Oscillation (WEMO). The results show that warming is a complex phenomenon at regional and sub-regional scales that can only be analysed using high-spatial-resolution data and considering global and local factors