Explanation of temporal changes of isotopic composition in precipitation in Hungary by meteorological data and satellite images

The aim of this work is to get a time series of the tritium content and delta values of oxygen and deuterium of precipitation characteristic for Hungary and to identify those factors, which have essential influence on the temporal changes. There are three main moisture sources, which determine the weather and the raining above Hungary. One of them is the Atlantic Moisture Source, which comes from the West bringing moisture from the mid-latitude Atlantic water vapour. The second main source of water is the Baltic Mositure Source. It brings moisture from the Arctic region over the Baltic Sea. The third source is the Mediterranean Moisture Source, which carries water from the South-West. The rainfall events are continuously sampled in Debrecen, East-Hungary from December 2000. Tritium, deuterium, and oxygen-18 content of the precipitation samples are measured. We have found that the tritium content of the precipitation changed between 4.8 and 18.0 TU in 2001, between 4.4 and 20.3 TU in 2002, and between 3.5 and 19.8 TU in 2003, with an average of 10.4 ± 0.3 TU, 10.7 ± 0.3 TU and 8.7 ± 0.3 TU, respectively. The decreasing in the average tritium concentration of precipitation in 2003 was due to the very wet winter, while the year 2001 and 2002 were quite similar from the point of view of raining. On the basis of satellite images (EUMETSAT 2001-2004) and meteorological data we determine trajectories in order to decide which moisture source brings the water vapour. On the one hand the isotopic composition of precipitation depends on the moisture source, which provides the rainfall. On the other hand, the seasonal, continental and latitude effects have to be taken into account to explain the temporal changes. Sharp peaks in the tritium concentration of rain appear in early summer ('spring leak') as a consequence of the exchange between the troposphere and the stratosphere. We would like to understand better how this exchange mechanism works