Abstract
Evidence for a close relationship between the interannual variation of stable isotopes in precipitation and the El Ñino Southern Oscillation (ENSO) is presented for Bangkok, Thailand. Anomalies of sea surface temperature in the Niño‐3 region of the equatorial Pacific (ENSO index) and δ^18^O in precipitation in Bangkok were positively correlated for May and October. The composite mean precipitation was much greater in the isotopic low phase than in the high phase for both May and October. This suggests that the amount of precipitation is the main factor determining the observed variation of stable isotopes in precipitation in Bangkok. Composite analyses of 850 hPa temperature, evaporation, outgoing longwave radiation (OLR), and precipitation showed that the variation in the amount of precipitation in Bangkok is a response to the ENSO–Asian summer monsoon coupling in May, and a direct response to ENSO in October. The composite mean d‐excess values in both the low and high phases in October and in the low phase in May were about 10‰, and were less than 7‰ during the high phase in May. A large difference in the evaporation field between the low and high phases of May exists over the Indian Ocean, suggesting that evaporation was not in equilibrium during the high phase in May. Future studies will consider the precipitation amount effect based on daily or event‐based sampling. Copyright © 2005 John Wiley & Sons, Ltd.