Climatic variations at Trieste during the last century

Abstract

The time series of the annual values of eight climatic elements (atmospheric pressure, air temperature, relative humidity, precipitations, "bora" and southerly winds frequencies, sunshine duration and sea level) recorded at Trieste , northern Adriatic , in the years 1871 - 1985 are reported and analysed. The characteristic spectra are computed by means of least squares method: the most significant periods are 50, 24, 18.30, 12.70, 10.90, 7.80, 4.96, 4.62, 3.67, 3.42, 2.97, and 2.25 years, the last one corresponding to the quasi-biennial oscillation of 27 months.

The linear trends show an almost stationary pressure, an increase of the air temperature (+ 0.003°C a -1 ), a decreasing relative humidity (- 0.03% a -1 ), decreasing precipitations (- 1.5 mm a -1 .), a reduction of "bora" and an increase of southerly winds (- 0.3 and + 0.3 days per year respectively), a reduction of the sunshine duration (- 1.6 h a -1 ) and an increase of the sea level (+ 0.13 cm a -1 ).