THE SNOW REGIME IN THE NORTHERN PART OF MOUNT VELEBIT

The snow conditions in the Dinaric Alps are of great importance on a global scale for the albedo and heat balance, on a regional scale for support of ground water or because of possible flooding in the karst lowland area, and on a local scale for the vegetation season, the protection of the animal world, recreation and tourism, etc. These reasons initiated an investigation of the snow parameters at the main meteorological station Zavižan (1594 m a.s.l.,44°49\u27N, 14°59\u27E). It is the highest mountain station in Croatia, situated in the northern part of Mount Velebit and was established in 1953. The snow conditions are presented by means of the annual course and the probability of occurrence of different snow parameters, their time fluctuations and trend, and their correlation with other meteorological parameters, as well as the beginning and end of the snow season. The fluctuations during the 1953/1954 - 1992/1993 period are in accordance with the snow conditions in the Alps and The High Tatra mountains. During the analized period 1953/1954 - 1992/1993, snow was more abundant in the second half of the 1960s and 1970s as well as in the early 1980s. Winters with less snowfall, lower snow depth and shorter duration of snow cover are significatively correlated with warmer temperatures, higher air pressure and lower precipitation. The winter trend exhibits no significant decrease either in snowfall or in snow depth

Stationarity, Trend and Periodicity of Precipitation at the Zagreb-Grič Observatory from 1862 to 1990

This paper deals with the climatic change in the annual, warm half-year and cold half-year precipitation data during the last 129 years, since the beginning of the series in 1862 to 1990, at the Zagreb-Grič Observatory (φ = 45° 49\u27, λ = 15° 59\u27, H = 159 m a.s.l.) located in the northwestern part of Croatia. The analysis has been deduced by using tests for normality, the "quick test" for stationarity according to Schönwiese and Malcher, weighted moving average filters, the Mann-Kendall rank statistic for trend, and the power spectrum analysis. This analysis shows the stationarity of time series of precipitation amounts. A generally decreasing, not statistically significant trend is present over the entire time interval (1862-1990). The annual and warm half-year precipitation spectra can be fitted by Markov "red noise" continuum and the cold half-year precipitation series by that of "white noise". Quasi-periodic oscillations appear in two spectra ranges: short (2 - 6 years) and medium (16 - 43 years)

Varijabilnost prosječnog oborinskog režima šire zagrebačke regije

Varijacije godišnjih količina oborine Zagreb - Grič u razdoblju od 1862--1980. prikazane su krivuljom izglađenom pomoću 9-godišnjih otežanih kliznih srednjaka i njoj pridruženim polinomom 12. stupnja. Testiranjem trenda pomoću Spearmanovog testa korelacije ranga utvrđeno je da postoji signifikantna stacionarnost vremenskog niza, te se ne može konstatirati prisutnost trenda Za 4 reprezentativne stanice u gradu i okolici je pokazano da utjecaj unbanizacije i industrijalizacije na godišnje količine oborine i količine oborine toplog dijela godine nije prisutan. Nakon ispitivanja normale oborinskog niza (godišnjih količina oborine i količina oborine veljače i srpnja) Zagreb-Griča, odabran je 20-godišnji niz sredine druge polovice XX stoljeća za analizu prostorne raspodjele godišnjih i mjesečnih količina oborine Zagreba i šire regije. Nadalje, za mjesece u kojima se javljaju ekstremi u godišnjem hodu oborine (II i VII) provedeno je pridruživanje teorijske razdiobe čestina empiričkim razdiobama za Zagreb-Grič i Puntijarku

OCJENA TEMPERATURNIH I OBORINSKIH PRILIKA KOLOVOZA 2005. DUŽ DIJELA ISTOČNE JADRANSKE OBALE

U kolovozu 2005., posebice u prvoj dekadi, istočnu jadransku obalu zahvatila su dva vremenska poremećaja popraćena značajnim padom temperature zraka i obilnijom oborinom, što nije uobičajeno za taj dio ljeta. Ocjena ovih izvanrednih pojava provedena je pomoću podataka s meteoroloških postaja: Rijeka, Mali Lošinj, Zadar, Hvar i Dubrovnik, i to srednjih dnevnih temperatura zraka za kolovoz (1948-2005) i količine oborine u prvoj dekadi kolovoza (1961-2005). Ocjenjivanje je provedeno pomoću dvije metode: kriterija standardne devijacije i kriterija percentila. Kao referentno razdoblje korišteno je standardno klimatološko razdoblje 1961-1990. U promatranih 57 godina, samo je kod 7 godina prva dekada kolovoza bila hladnija od prve dekade kolovoza 2005. barem na jednoj od pet postaja. Samo kod dvije godine (1955. i 1976.) prva dekada kolovoza bila je na svim postajama hladnija od prve dekade kolovoza 2005. Prema kriteriju percentila, gledajući izdvojeno prvu dekadu kolovoza 2005., pokazalo se da su postaje Rijeka i Mali Lošinj bile u kategoriji vrlo kišno (>91%), dok su Zadar, Hvar i Dubrovnik bili u kategoriji kišno (>75%)

CLIMATOLOGICAL BASIS FOR PREDICTION OF TEMPERATURE REGIME ON GROUND

Data on air and road surface temperatures not beeing available, climatological data from the site of the meteorological station have been used to determine the temperature relations needed for predicting road slipperiness. The analysis has been made for the cold period of the year (September to May) for the 10-year period 1971-1980 at the Zagreb-Maksimir station, located in the Sava River valley at the foot of Mount Medvednica. The analysis involves the relations between minimum air temperatures at two levels, 2 m and 5 cm as well as between minimum air temperatures at 2 m height and soil temperatures at 5 cm depth at 7 a.m. during various weather situations, defined according to average cloudiness, wind conditions, fog and frozen ground during the night preceding the occurrence of minimum temperatures. In weather situations with prevailing radiation processes (clear/calm and partly cloudy/calm), the minimum surface air temperatures are always lower than at 2 m height. On the other hand, after cloudy nights, regardless of wind velocity, the minimum surface temperatures are lower than those at 2 m only above determined temperature levels. The minimum air temperatures at 5 cm height are lower than 0°C when the minimum temperatures at 2 m height are lower than 3°C during clear/calm, clear/windy and partly cloudy/calm situations. During partly cloudy/windy, cloudy/calm and cloudy/windy situations, the differences between minimum temperatures at these two levels are smaller, and consequently, negative minimum surface temperatures appear if the minimum temperatures at 2 m are about 0°C. The relations between minimum air temperatures and soil temperatures do not differ significantly for different weather types. However, they differ considerably from month to month. According to these conclusions, soil temperatures should be predicted particularly by means of regression equations obtained for each month

ESTIMATON OF MAXIMUM SHORT-TERM PRECIPITATION OVER THE RIJEKA REGION

In this paper, we considered the occurrence of extreme short-term rainfall in the region of Rijeka city, analyzed the extreme values, and commented on application of the results. We estimated the maximum precipitation amounts for different occurrence probabilities (return periods) for time intervals of 5, 10, 20, 30, 40, and 60 minutes, as well as 2, 4, 8, 12 and 24 hours, using data taken at the Rijeka meteorological station over periods of 1958–2011 and 1958–2012. Additionally, we evaluated the extremity of a heavy rainfall event that affected the city of Rijeka on September 12th, 2012. Using absolute extremes recorded for time intervals of 20 minutes to 2 hours, we accounted for precipitation peaks to calculate new intensity–duration–return period curves for Rijeka. In this way, we revised the precipitation input parameters used to plan and design urban drainage systems. This revision included significant changes for durations of 20, 30, and 40 minutes, for which the amounts recorded on September 12th, 2012 had return periods of longer than 100 years

CLIMATOLOGICAL BASIS FOR PREDICTION OF TEMPERATURE REGIME ON GROUND

Data on air and road surface temperatures not beeing available, climatological data from the site of the meteorological station have been used to determine the temperature relations needed for predicting road slipperiness. The analysis has been made for the cold period of the year (September to May) for the 10-year period 1971-1980 at the Zagreb-Maksimir station, located in the Sava River valley at the foot of Mount Medvednica. The analysis involves the relations between minimum air temperatures at two levels, 2 m and 5 cm as well as between minimum air temperatures at 2 m height and soil temperatures at 5 cm depth at 7 a.m. during various weather situations, defined according to average cloudiness, wind conditions, fog and frozen ground during the night preceding the occurrence of minimum temperatures. In weather situations with prevailing radiation processes (clear/calm and partly cloudy/calm), the minimum surface air temperatures are always lower than at 2 m height. On the other hand, after cloudy nights, regardless of wind velocity, the minimum surface temperatures are lower than those at 2 m only above determined temperature levels. The minimum air temperatures at 5 cm height are lower than 0°C when the minimum temperatures at 2 m height are lower than 3°C during clear/calm, clear/windy and partly cloudy/calm situations. During partly cloudy/windy, cloudy/calm and cloudy/windy situations, the differences between minimum temperatures at these two levels are smaller, and consequently, negative minimum surface temperatures appear if the minimum temperatures at 2 m are about 0°C. The relations between minimum air temperatures and soil temperatures do not differ significantly for different weather types. However, they differ considerably from month to month. According to these conclusions, soil temperatures should be predicted particularly by means of regression equations obtained for each month

Climate change and the influence on health

Povećana koncentracija stakleničkih plinova zbog ljudskih aktivnosti uzrokovala je globalno zatopljenje koje je u proteklom stoljeću bilo najveće u posljednjih 1000 godina. Zatopljenje je zabilježeno i u Hrvatskoj, gdje je temperatura na obali porasla više nego u unutrašnjosti, pri čemu je zatopljenju na obali najviše pridonio porast ljetnih, a u unutrašnjosti zimskih temperatura zraka. Klimatske promjene utječu na zdravlje ljudi, pri čemu se najviše ističe povećana smrtnost za toplinskih valova, čija se učestalost također povećava s globalnim zatopljenjem. Infektivne bolesti osobito su podložne vremenskom utjecaju, jer vrijeme, pa tako i klimatske promjene, utječe na sve sudionike transmisijskog ciklusa –patogene, prijenosnike i ljude.The increased concentration of greenhouse gases caused by the human activities has an impact on the global warming, the highest one during the last 1000 years. The warming has been also observed in Croatia. The air temperature increased along the Croatian Adriatic coastland more than in the mainland. Summer temperature increase contributed at most to the annual increase at the coast, and the winter temperature increase over the inland. Climate change has an impact on the human health, mostly expressed in an increased mortality during heat waves, whose frequency has also increased with the global warming. Infectious diseases are especially subject to weather influence, because weather, and thereby climate changes, influence all participants in the transmission cycle – pathogens, vectors and humans

Sekularni trend indeksa oborinskih ekstrema u Hrvatskoj, 1901.–2008.

In this study, trends in annual and seasonal precipitation amounts in Croatia are discussed. This discussion is followed by trend analysis in seven indices of precipitation extremes, which indicate intensity and frequency of extreme rainfall events. These indices have been proposed by World Meteorological Organisation and are calculated using daily precipitation amounts. The data sets used in this study cover the period 1901–2008 at five meteorological stations distributed among different climate conditions in Croatia: continental, mountainous and maritime. The trends are estimated by a simple least squares fit of the linear model and tested for statistical significance by a non-parametric Mann-Kendall test. The time series with significant trends are identified, and a Sneyers progressive analysis is then performed to determine the beginning of the trend. The time series analysis of coefficients of variation in consecutive 30-year periods indicates the variability in precipitation. The extreme quantiles for annual one-day and five-day precipitation maxima have been estimated by the Generalised Extreme Value (GEV) distribution and discussed in relation to the original time-series. The results show a downward trend in annual precipitation amounts since the beginning of the 20th century throughout Croatia, which agrees with the drying trend observed across the Mediterranean. Precipitation amounts have large interannual variability, on both annual and seasonal scales. By the end of the 20th century, the precipitation variability decreased in the north-western Croatian mountainous and northern littoral regions and the eastern lowlands. The Dalmatian islands experienced increased variability since the middle of the 20th century. In regions of drying, such as Croatia, there is no evidence of major secular changes in precipitation extremes that are related to the high amounts of precipitation and the frequency of heavy rainfall days over the majority of Croatia.U ovom je radu uvodno diskutiran trend godišnjih i sezonskih količina oborine u Hrvatskoj, a potom je analiziran trend sedam indeksa oborinskih ekstrema koji ukazuju na intezitet i učestalost ekstremnih oborinskih događaja. Te je indekse preporučila Svjetska meteorološka organizacija, a računaju se pomoću podataka dnevnih količina oborine. Analiza je provedena za razdoblje 1901.–2008. za pet meteoroloških postaja smještenih u različitim klimatskim uvjetima: kontinentalni, planinski i maritimni. Trend je procijenjen jednostavnim modelom linearne regresije, a statistička značajnost trenda je testirana pomoću Mann-Kendallovog neparametarskog testa. Za nizove sa statistički značajnim trendom primijenjen je i Sneyersov progresivni test za trend kako bi se odredio početak uočenog trenda. Varijabilnost godišnjih količina oborine je izražena vremenskim nizovima koeficijenta varijabilnosti izračunatih za 30-godišnja razdoblja s pomakom od jedne godine. Nizovi godišnjih jednodnevnih i petodnevnih maksimalnih količina oborine su posebno analizirani usporedbom s ekstremnim kvantilima, koji su određeni primjenom opće razdiobe ekstrema (GEV). Rezultati pokazuju da je od početka 20. stoljeća u Hrvatskoj prisutan negativni trend godišnje količine oborine, čime se ovo područje pridružuje tendenciji osušenja na Mediteranu. Varijabilnost količina oborine se smanjunje u sjeverozapadnoj Hrvatskoj, u gorju, na sjevernom primorju i u istočnom nizinskom području. Na dalmatinskim otocima je u razdoblju od sredine 20. stoljeća prisutno povećanje varijabilnosti. Iako se radi o području osušenja, u većem dijelu Hrvatske nisu utvrđeni znakovi većih promjena u ekstremima, kako količina oborine tako i učestalost vlažnih i vrlo vlažnih dana

Drought Vulnerability in Croatia

Drought is the most frequent hazard causing the highest economic losses among all hydro-meteorological events in Croatia, especially in the agricultural sector. Climate assessment according to aridity index shows that susceptibility to desertification is present in the warm part of the year and mostly pronounced in the Adriatic region and eastern lowland. Evidence of higher frequencies of extreme droughts in the last decade has been noted. These were the motivations to study the drought risk assessment in Croatia and to develop a vulnerability map. This map is a complex combination of the geomorphologic and climatological inputs (maps) that are presumed to be natural factors which modify the amount of moisture in the soil. The first version of the vulnerability map developed from the slope map, solar irradiation and coefficient of the variation of precipitation is updated by inclusion of optional parameters: soil types and land cover classes. The recommended procedure in the framework of Drought Management Centre for Southeastern Europe is modified and adopted in this study. The obtained results for Croatia show the areas most sensitive to drought to be on the southern Adriatic coast and over the eastern continental lowland