A 225-year pine (Pinus latteri) tree-ring record of pre-monsoon relative humidity variation in Nan province of northern Thailand and the linkage with large-scale ocean-atmospheric circulations

Thailand is bounded by the Gulf of Thailand in the Pacific Ocean and the Andaman Sea in the Indian Ocean. Variations in the Thailand monsoon (TM) are strongly influenced by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) phenomenon. The climatology of Thailand is of great importance for understanding seasonal responses to large-scale climatic variations and associated ocean-atmospheric forcing. This study presents the first longest reconstruction (1792–2016 CE) of March–May relative humidity (RH) based on the tree-ring width chronology of Pinus latteri trees from Nan province, northern Thailand. The growth of P. latteri was mainly limited by pre-monsoon RH variability (r = 0.773, p