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J. Martinez-FrÍAs A. Delgado M. MillÁN E. Reyes F. Rull D. Travis R. Garcia F. LÓPez-Vera J. A. RodrÍGuez-Losada J. A. Martin-Rubi J. Raya E. Santoyo 《Journal of Atmospheric Chemistry》2005,52(2):185-202
Specific studies about the stable isotope composition (18O/16O and D/H) of atmospheric icy conglomerations are still scarce. The present work offers, for the first time, a very detailed
analysis of oxygen and hydrogen isotopic signatures of unusually large ice conglomerations, or “megacryometeors”, that fell
to the ground in Spain during January 2000. The hydrochemical analysis is based on the bulk isotopic composition and systematic
selective sampling (deuterium isotopic mapping) of eleven selected specimens. δ18O and δD (V-SMOW) of all samples fall into the Meteoric Water Line matching well with typical tropospheric values. The distribution
of the samples on Craig's line suggests either a variation in condensation temperature and/or different residual fractions
of water vapour (Rayleigh processes). Three of the largest megacryometeors exhibited unequivocally distinctive negative values
(δ18O = −17.2%0 and δD = −127 %0 V-SMOW), (δ18O = −15.6%0 and δD = −112%0 V-SMOW) and (δ18O = −14.4%0 and δD = −100%0 V-SMOW), suggesting an atmospheric origin typical of the upper troposphere. Theoretical calculations indicate that the vertical
trajectory of growth was lower than 3.2 km. During the period in which the fall of megacryometeors occurred, anomalous atmospheric
conditions were observed to exist: a substantial lowering of the tropopause with a deep layer of saturated air below, ozone
depression and strong wind shear. Moreover, these large ice conglomerations occurred during non-thunderstorm conditions, suggesting
an alternative process of ice growth was responsible for their formation. 相似文献
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