Using stable isotopes to study vapor transport of continuous precipitation in Beijing

To study changes in water vapor transport during continuous precipitation, stable isotope data, NCEP/NCAR data and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) backward trajectory results during 22 continuous precipitation events in Beijing are analyzed. The results indicate that there are five different vapor transport types for the 22 continuous precipitations:westerly vapor transport, remote oceanic vapor transport, vicinal oceanic vapor transport, remote continental vapor transport, and vicinal continental vapor transport. Vicinal oceanic vapor transport and westerly vapor transport are predominate vapor transport types, contributing to 60.8% of the total precipitation. Variations of precipitation δ¹⁸O signals in different vapor transport types are mainly caused by differences in isotopic components in the source regions and the upstream rainout processes along the vapor transport pathways. Changes in deuterium excess reveal the influence of re-evaporation during precipitation and the humidity conditions in the vapor source areas. Fourteen continuous precipitation events are controlled by different vapor transport types at different stages, and the variations in precipitation δ¹⁸O indicate the changes in vapor transport types. These results show that isotope signals in precipitation can provide useful information for identifying vapor transport types.