Aridity and soil moisture deficit trends

A change in climate may cause either or both precipitation and potential evaporation to change. The one binding factor to all arid areas is aridity. Aridity is usually expressed as a function of rainfall and temperature. A useful description of aridity is the following climatic aridity index - P/PET. Climatic data (monthly air temperature and sum of precipitation) for four meteorological stations (Kaunas (Lithuania), Horki (Belarus), Sisak (Croatia) and Sarajevo (Bosnia and Hercegovina) for the period 1996–2016, were used for analysis of agrohydrological balance components by Thornthwaite-Mather method (TM). The movement of temperature and aridity zones could trigger ecosystem migration and land use change. According to the aridity index, based on temperature and rainfall as weather parameters, the climate dryness risk was analyzed. The biggest monthly potential evapotranspiration was in July in all stations in the last 20 years. Monthly soil water balance was found negative in all stations: quantity amount bigger in Sisak and Sarajevo, but continuous longer in Kaunas and Horki. Yearly soil moisture deficit was observed nearly every year at all meteorological stations too. Results showed increasing trends in surface air temperature (in all four meteorological stations) and precipitation (decreasing in Sarajevo). The annual summer P/PET of the study areas varied between 0.6 and 0.9. A drought coefficient has been increasing in Kaunas and Sarajevo in the last 20 years. Information regarding changes in P/ETo index as a result of climate change is necessary for policy makers and managers within the context of water resources management, hydrology, agriculture, and environmentVytauto Didžiojo universitetasŽemės ūkio akademij