A 9-year record of stable isotope ratios of precipitation in Eastern Hungary: Implications on isotope hydrology and regional palaeoclimatology

The stable isotopic composition of hydrogen and oxygen of precipitation from Debrecen, Eastern Hungary was analysed in event-based samples collected from the beginning of 2001 to the end of 2009. During the monitoring period, the δ18O values varied between −22.3‰ and 6.64‰ and the δ2H values between −176.8‰ and 10.7‰. The LMWL for the monthly based data is close to the GMWL, but shows the effect of secondary evaporation of falling raindrops with lower intercept and slope. LMWL of each year shows highly different parameters due to differences in precipitation amount and summer temperatures, especially in the extreme years of 2002 and 2003. On the basis of our data, deuterium excess is considered to be the best parameter to reveal the extremities of dry and warm periods. Deuterium excess also proved to be a useful tool to show the different formation histories of certain precipitation events. Good correlation of δ18O with temperature was obtained for the samples. The slope of the δ18O–T functions for the whole sampling period was 0.32 ± 0.03‰/°C for the monthly samples, however, a slope of 0.37 ± 0.03‰/°C was obtained if monthly mean temperatures were replaced with the monthly mean temperatures of the rainy days. Considering the temperature dependency of the δ18O values in the past, it can be concluded that Δδ18O/ΔT relationship using monthly mean temperatures of the rainy days might be a better approach than monthly mean temperatures.