A tree-ring cellulose δ18O-based July–October precipitation reconstruction since AD 1828, northwest Thailand

• This is the first well-replicated tree-ring δ18O chronology for the period 1828–2000 in northern Thailand.
• The tree-ring δ18O is a promising proxy to reconstruct precipitation.
• The tree-ring δ18O shows a close relationship with ENSO from 1871 to 2000, with the exception of during the last two decades.

SummaryA tree-ring δ18O chronology for the period 1828–2000 was developed from four Pinus merkusii trees, to find a reliable proxy for reconstructing precipitation in northwest Thailand. Inter-tree δ18O correlations were high during the entire period (r = 0.57–0.79). The tree-ring δ18O chronology shows significant negative correlations with regional July–October precipitation during the period 1901–2000 (r = −0.62) and with July–October river flow (r = −0.54), and is in good agreement with a shorter tree-ring δ18O chronology from living Pinus kesiya in northwest Thailand. The spatial correlation analysis between tree-ring δ18O and regional July–October precipitation also support that the tree-ring δ18O of P. merkusii is a promising proxy to reconstruct precipitation in northwest Thailand. The tree-ring δ18O-based July–October reconstruction, which accounts for 37.6% of the precipitation variance, shows a close relationship with El Niño–Southern Oscillation (ENSO) during the period 1871–2000, with the exception of during the past two decades; the exception may be related to the southeastward shift of the descending limb of Walker circulation and increased frequency of central Pacific ENSO.