Precipitation isotope characteristics and climatic controls at a continental and an island site in Northeast Asia

Abstract

In mid-latitude continental and island regions, the isotope composition of air masses often varies according to both their origin and their interaction with topography along their path of travel. Comparison of stable isotopes in continental and island precipitation events can reveal climatic controls upon isotopic content and yield information about patterns of atmospheric circulation. The overall deuterium (D) and oxygen-18 ( 18 O) characteristics of 64 precipitation events observed in continental Beijing, China, and 109 precipitation events observed at Seongsan (Jeju Island, Republic of Korea) were investigated. The established local meteoric water lines, D = 7.49 18 O + 1.53 (R 2 = 0.96, n = 64) and D = 8.36 18 O + 19.05 (R 2 = 0.86, n = 109), indicated periodic drought in Beijing and a kinetic effect in the condensation process in Seongsan. To trace moisture origins and transport paths for all precipitation events, the 96 h backward trajectories of air masses arriving at 3000 m above ground level were calculated and categorized using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results indicate that during the Asian monsoon period, the air mass categories represented at Seongsan were principally from the southeast, southwest, and continental vicinity (CV). Those observed for Beijing were more varied (northwest, west, north, marine vicinity, south, and CV). Additionally, the meteorological controlling factors of each air mass category were identified using non-linear stepwise regression. The precipitation amount was the main predictor for 18 O in precipitation in Seongsan, while the controlling factors involved in Beijing were more complicated.