The influence of regional and global climatic oscillations on Croatian climate

摘要

We apply spectral analysis and sliding window correlations to monthly, seasonal, and annual climatological data from station records throughout Croatia going back to 1859 in order to investigate the potential influences of a set of important climatic drivers, including solar variability, and ocean-atmosphere oscillations in both the Pacific realm (El Ni?o-Southern Oscillation, ENSO and Pacific Decadal Oscillation, PDO) and the Atlantic realm (Atlantic Multidecadal Oscillation, AMO and North Atlantic Oscillation, NAO). In addition to a general long-term warming and drying, there are significant interannual to decadal scale variations. Positive phases of AMO correspond to higher Croatian temperatures and also times of greater interannual temperature variability. Higher frequency variations in NAO are positively correlated with temperature such that a negative phase of NAO is associated with lower Croatian temperatures. The strength of NAO's influence is modulated by the long-term cycles of AMO; stronger during positive decadal-scale phases of AMO. ENSO exerts a weaker influence on temperatures, and is only significant during positive phases of the PDO. NAO has a strong influence on Croatian winter precipitation, with negative NAO phases corresponding to higher precipitation, modulated by the longer term phases of AMO. Although weaker and less consistent, ENSO also influences Croatian winter precipitation, modulated by longer term cycles of the PDO. Both NAO and ENSO show signs of frequency-dependent correlation; NAO is influential at cycles of 8-9 and 2.4 yr in the Adriatic-Dinaric part of Croatia, while ENSO is especially influential at a 3.6 yr cycle in the Pannonian region. The influence of solar variability is apparently much weaker than that of NAO and ENSO, yet there is a remarkably coherent correlation between amplitude modulation of winter precipitation in the Pannonian region and the sunspot record.