What causes site-specific intra-event variations of stable isotopes in precipitation in Beijing?

Stable oxygen isotope composition (δ18O p) and deuterium excess (d p) in precipitation carry important climate and hydrological information on the history of water from evaporation, transport to precipitation. This study aims to quantify the effect of potential factors on site-specific intra-event δ18O p and d p dynamics during three precipitation events in a mid-latitude region Beijing, China. The tested factors included moisture source (M s) and upstream rainout fraction (U p) obtained by HYSPLIT backward trajectory model, radar reflectivity factor (Z e) that corresponds to raindrop size by weather radar, sub-cloud evaporation fractionation (f e) by an isotope-evaporation model, local precipitation amount (L p) and precipitation intensity (I) by rain gauge, and relative location of the sampling sites (downwind or upwind). Intra-event δ18O p had an amplitude of 10.3‰, and 84% of the variance could be explained, in the descending order of importance, by M s , site, Z e , f e and I. Intra-event d p had an amplitude of 16.5‰, and 57% of the variance could be explained by f e , site, M s and I , in the descending order of importance. Absolute values of intra-event δ18O p and d p differed between two sites, 30 km apart, by up to 4.7‰ and 9.7‰, respectively. This site-specificity in δ18O p and d p was mainly caused by differences in rainout effects and I. This work provides new insights into separating the effects of various climatic and hydrological variables on high-frequency dynamics of δ18O p and d p. • Intra-event δ18O p and d p vary largely over time and between neighboring sites. • Moisture sources and sub-cloud evaporation mainly impact intra-event δ18O p and d p. • Rainout and precipitation intensity cause site-specific intra-event δ18O p and d p. [ABSTRACT FROM AUTHOR]