Hydrometeorological factors controlling the time variation of D, 18O and 3H in atmospheric water vapour and precipitation in the northern westwind belt

Long-term records of D, 18O and 3H in daily composite samples of water vapour and precipitation, together with relevant hydrometeorological parameters, are presented for Heidelberg and Cracow. Short-period isotope records of the water vapour at Paris, Hannover and Miami are also discussed. The records of delta D and delta 18O in water vapour reveal strong short-term variations comparable with the range of their seasonal variation (Δ delta D approx.= 80 per mille and Δ delta 18O approx.= 10 per mille). A simple water vapour advection model simulates fairly well the seasonal variation of the monthly mean isotope data. The application of this Rayleigh condensation model to a description of the isotopic depletion along the trajectories of individual air masses yields isotope data at the observation point being in most cases inconsistent with the actual findings. This discrepancy is reflected by a poor temperature correlation for the daily isotope data, whereas monthly means are very well correlated (2.8 per mille/deg. C for delta D and 0.3 per mille/deg. C for delta 18O). A power spectral analysis of the delta D records yields a prevailing group of periodicities of 50-67, 29-36, 20-22 and 10-11 days. These moving 'wave patterns' show a constant phase shift of about one day between Heidelberg and Cracow. The 3H data of water vapour and precipitation show that the surface atmosphere over western and central Europe is permanently contaminated by quasi-continuous discharges of tritium from nuclear energy installations; the average level of this contamination is significantly lower than that observed in the preceding decade. (author)