Relative humidity variation derived from tree-ring δ18O and possible large-scale atmospheric circulations linkage over the Guanzhong Plain, central northern China, since 1760 CE

China is drastically influenced by the Asian monsoon. Based on the relationship (r = -.636, N = 62, p < .001) between tree-ring delta O-18 values from nine cores of Pinus tabulaeformis Carr. from Nanwutai and the Asia monsoon-related June-August relative humidity (RHJJA), we designed a transfer function reconstructing the RHJJA variation from 1760 to 2018 CE. Our RHJJA reconstruction captured some extreme climatic events that occurred in the past, such as the Ding-Wu disaster (1876-1878 CE), which was the most serious drought event of northern China in the 19th century, and the severe drought event of 1925-1930 CE. The spatial correlation analysis shows that our RHJJA reconstruction has not only local but also large-scale hydroclimate circulations. Our reconstruction compared well with other hydroclimate series from northern China, indicating the large-scale representativeness of our reconstruction. Both the ensemble empirical mode decomposition (EEMD) and the periodicity analyses revealed that the El Nino-South Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Arctic Oscillation (AO) and the solar activity strongly affected Asian monsoon-related RHJJA changes over Guanzhong Plain in the past. We believe this study is of great significance and provides an in-depth understanding of climate change in the Guanzhong Plain and in northern China.