AIR TEMPERATURE TRENDS AT SELECTED METEOROLOGICAL STATIONS AND TIME SERIES

1. Upward trends in time series of basic characteristics of air temperature at selected meteorological stations in Slovakia Pavol Faško1 – Pavel Šťastný1 – Marek Švec1 – Peter Kajaba1 – Oliver Bochníček1 (1) Slovak hydrometeorological institute Bratislava, Slovakia ABSTRACT Rise of the air temperature due to climate change in recent decades is very clear. When comparing the long-term average air temperature in the period 1951-1980 with the 1981-2010 period, the warming in the last thirty years was most noticable in January, May and summer months, while adequately to this average temperatures of individual seasons increased as well as the values of average annual air temperature. The period from March to September in 2012, was the warmest seven-month period in Hurbanovo from the beginning of meteorological measurements at this meteorological station since 1871. This fact was also reflected in other characteristics of the air temperature in Slovakia. The average monthly air temperatures in the last 25 years know represent the warmest months from the mid-20th century. This is also reflected in the trends of the average monthly, seasonal and annual air temperatures, which are in the charts expressed by fourth degree polynomial. These tendencies weren’t recorded just within the warmest regions of southwestern Slovakia (represented by station Hurbanovo), but throughout its entire territory, including the high mountain locations (represented by station Lomincký štít). The year 2012 was one of the warmest years in the history of meteorological measurements in Slovakia, however in addition to a period with several months with above-average air temperatures, there was one particularly frosty short period during the end of January and in the first half of February 2012. This trend may indicate an increased risk of higher fluctuations of the air temperature in the future. AIR TEMPERATURE TRENDS AT SELECTED METEOROLOGICAL STATIONS AND TIME SERIES Thecontentsofthepresentedimages show that in thetimeseriesofaveragemonthly, seasonal and annualairthegreatestrises in values ​​oftheaverageairtemperaturehavebeenrecordedsincethebeginningofthe 90's ofthe 20th century. This trend isnotthesame in allmonthsoftheyear and in all 4 seasons. Goodexamples are themonthsof November and December, in whichtheairtemperature trend in Hurbanovo (butalsoatotherlocationswithin Slovakia) isratherindifferent. The rate ofincreaseofaverageairtemperature has approximately in thelasttwodecadesalsosomeregionalaspects. Thisincreaseisrelativelylessapparent in southwestern Slovakia and converselyit's more significant in thevalleysofcentral Slovakia or in theeastern Slovakia. Theeffectsofglobalwarmingbeforethelastdecadeofthe 20th centuryweredefinitely more significant in thesouthwesternregionsof Slovakia than in theotherregionsof Slovakia. Thewinters in thevalleysofcentral Slovakia, are more humid and warmer in thelastdecadesthantheywereinthepast, whichmeansthat in theseregions, theamountofmixed and liquidprecipitationofthetotalprecipitationduringthewinterisgrowing. Decreaseofsnowcoverwasalsoregistered in theseareas and due to increasedcloudiness and precipitationthere are nowlesssuitableconditionsduringwinter, fortheoccurrenceofstrongnight and morningfrosts.On theotherhandthecloudiness in theseregionsislowerinthesummer, theamountoflong-termrainfallisdeclining, whichsupportsgreaterwarmingofthesevalleys. The end resultisthatthegrowthofaverageannualairtemperature in theseareasisgreater, thanitisforexample on theDanubelowland. Thesameapplies to eastern Slovakia, wheretheregistereddecreaseofsnowcovercausesthatconditionsforcoolingofairabovethesnowcover are nowlesscommon (temperaturedifferencesbetweenwinter and summer has becomelesssignificant). In 2012, thechangesoftemperatureconditions in Slovakia wereveryinteresting. Thetrendsfromthepreviousperiodswereconfirmed to suchextentthattheaveragemonthlyairtemperature in most monthsofthe 2012 wasagain on theleadingpositions, in hierarchicalorderofmonthlyairtemperaturevalues ​​sincetheyear 1951 (Fig. 4). Thetimeseriesofaverageannualairtemperatures in Hurbanovo since 1871 show thatthewarmestyear in thislocation so farwas a year 2000, withanaverageannualairtemperatureof 12.1 °C (1961-1990 temperaturenormalis 10.0 °C). VeryinterestingisthefactthatthehighestmeanannualairtemperatureattheSlovakia’shighestmountainstation - Lomnický štít (withairtemperaturemeasurementssince 1940) wasrecorded in 2011. Fig. 1The average monthly air temperature in different months of the year at selected meteorological stations since 1951 Fig. 2The average air temperature in summer (June-August) and winter (December-February) at selected meteorological stations since 1951 Fig. 3The average annual air temperature at selected meteorological stations since 1951 Fig. 4Ten warmest and ten coldest months since 1951 at selected meteorological stations (*months of the last 25 years are marked by red color) CONCLUSIONS • The period from March to September in 2012 was the warmest such seven-month period beginning in Hurbanovo from meteorological measurements at the meteorological station in 1871. This fact is also reflected in other characteristics of the air temperature in Slovakia. The average monthly temperature in last 25-years warmest months are mostly from the mid-20th century. This was also reflected in trends in average monthly, seasonal and annual air temperatures, which were expressed quartic polynomial. • Acknowledgment: This work was part of the project "Development of technology of spatial data processing of the climate system" ITMS 26220220102, and "Applied research of methods for determining the climatic and hydrologic design parameters", ITMS 26220220132 funded from the EU Structural Funds REFERENCES Faško, P. – Lapin, M. – Pecho, J.: 20-year extraordinary climatic period in Slovakia. In Meteorological Journal, 11, č. 3, s. 99 – 105, obr. 14. Petrovič, Š. et al.: Klimatické pomery Hurbanova. IClimatic conditions at Hurbanovov). HMÚ, Praha, 1960, 278 s. Fig. 5Avearege air temperature [°C] in the period from march to september in the years 1871-2012 at meteorological station Hurbanovo