TIME SERIES ANALYSES OF CLIMATOLOGICAL RECORDS FROM A HIGH ALTITUDE OBSERVATORY IN SOUTHERN ITALY (MONTEVERGINE, AV)

In this work we show the results obtained from the homogenization and the analysis of a climatic time series (mean temperature and total precipitation) collected in the Southern Italy Apennines (Montevergine, AV). This climatological time series is one of the oldest of Apennines mountains and it’s very meaningful for the high altitude region climate study, being located at 1280 m asl (40° 56°N, 14° 43’E). The homogenization of time series is performed using the Standard Normal Homogeneity Test and its non-parametric version. Precipitation time series is characterized only by a discontinuity, occurred on 1950, while temperature time series is affected by multiple inhomogeneities, caused by changing in instruments location, human errors and instruments accuracy degradation. The analysis of homogenized time series is carried out through Wavelet Analysis, in order to investigate about series behavior in time-frequency spectrum, and LOWESS smoothing, aiming to highlight the decadal variability; moreover, we use a linear polynomial model to define trends. The results highlight an increase in annual mean temperature of 0.5°C/100 years and a decrease in annual total precipitation of 32%/100 years (-667 mm/100 years). Positive temperature trend is evident on all seasons, except on autumn, while negative precipitation tendency is particularly sharp on spring. The signals are characterized by a strong oscillation between 1940 and 1950 on 2-4 years period. The opposite trends that characterize temperature and precipitation are very steep from mid-1970s up to early 2000s; in this period the two parameters are strongly anti-correlated, unlike previous decades, in which they show an unstable coupling. Mediterranean Circulation Index (MCI) captures a large portion of precipitation variability, while thermal regime is strongly related to Eastern Mediterranean Pattern (EMP).