engleski

The phenological fluctuations as a possible signal of climatic changes

The Gospić meteorological station was established in November 1872 and it is the station with the longest series of observations in the Croatian mountain area. In 1953 the observations of development stages of certain plants (phenological observations) have started at the Gospić station. Generally, in order to identify the climatic variations in specific region according to phenological data, plants that grow freely in the nature without any agro-technical practice added or the long-term observations of the same phenological object should be analysed. For the Gospić station the wild herbaceous plants satisfy the first condition ; the fruit trees the second condition and the forests trees and bushes both conditions. Thus, linear trends of development stages of the wild herbaceous plants (snow drop, saffron, dandelion and oxeye daisy), the forests trees and bushes (buckeye, locus-tree, weeping ash, birch, lilac, bour tree, white thorn, black thorn, hazel and cornel tree) and fruit trees (apple, peach and plum) have been analysed at the Gospić station during the available periods (mainly 1954-2004). The results of linear trend analysis and the Mann-Kendall test indicate the significant earlier blooming for the plants which bloom in the second half of April and May. The trend analysis of the leafing of peach trees and lilac and the yellowing of leaves of weeping ash have been shown significant trend at the 0.05 level in sense of earlier commencement of leafing and later yellowing. Those fluctuations are the consequence of significant increase in winter and spring insolation duration what cause increase in the mean spring maximum and winter minimum temperature and decrease in number of the freezing days. The trend analysis of the secular time series of other meteorological data show significant increase in the annual values of mean air pressure, mean and absolute minimum temperature, insolation duration and number of dry days, and decrease in annual precipitation amount, mean and minimum relative humidity and number of days with precipitation >= 10 mm (but increase in number of rainy days >= 0.1 mm). Such progressive growth in stability of the dry weather depends on recent prevailing meridional circulation rather than zonal over the Atlantic and Europe.

phenological observations ; linear trend ; climatic variations ; the mountain Gospić station

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