engleski

Analyses of the Zagreb Grič observatory air temperatures indices for the period 1881 to 2017

The paper studies time series of characteristic (minimum, mean and maximum) daily, monthly and yearly air temperatures measured at the Zagreb Grič Observatory in the period from 1 Jan. 1881 to 31 Dec. 2017. The following five air temperatures indices (ATI) are analysed: (1) absolute minimum yearly, monthly and daily ; (2) mean yearly, monthly and daily minimum ; (3) average mean yearly, monthly and daily ; (4) mean yearly, monthly and daily maximum ; (5) absolute maximum yearly, monthly and daily. Methods of Rescaled Adjusted Partial Sums (RAPS), regression and correlation analyses, F-test and t-tests are used in order to describe changes in air temperature regimes during 137 years. Using RAPS method the five analysed yearly ATI time series duration of 137 years were divided into two subperiods. The analyses made in this paper showed that warming of minimum air temperatures started in 1970, mean air temperatures in 1988 and maximum air temperatures in 1998. Results of t-tests show extreme statistically significant jump of air temperatures average values in second (recent time) subperiods. Results of t-tests of monthly temperatures show statistically significant differences between practically all five pairs (except in two cases) of analysed monthly ATI subseries for the period from January to August. From September to December for most of pairs (except in six cases) of analysed monthly ATI subseries differences are not statistically significant. It can be concludes that the urban heat island higher influenced increase of temperatures in recent time than global warming. It seems that urbanisation firstly and by the strongest way influenced on the minimum temperatures. It seems that Zagreb City urbanisation firstly and on the strongest way influenced on minimum than on maximum temperatures. Increasing trend in time series of maximum temperatures started 20 years later.

minimum ; mean and maximum ; daily ; monthly ; yearly air temperatures ; global warming ; urban heat island ; trend ; jump ; Zagreb Grič (Croatia)

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