Spatiotemporal variability of palmer drought severity index inferred from long tree-ring chronologies in the Russian and Mongolian parts of the lake Baikal basin

The spatiotemporal variability of moisture conditions in the Lake Baikal basin, a key region of Inner Asia, remains insufficiently understood due to the short duration of instrumental observations and the complex interplay of climatic factors. In this study, we reconstructed the self-calibrating Palmer Drought Severity Index (PDSI) for May–July using four long tree-ring chronologies from the Russian and Mongolian parts of the Baikal basin. Linear models explain 34–57% of the interannual variance in the instrumental PDSI. The 11-year smoothed mean PDSI values reveal alternating periods of in-phase and out-of-phase moisture variability between the two parts of the basin over the past ~250 years, while long-term (30-year) series show divergent trends: increasing moisture availability in the northern (BRG) and southwestern (HEC) parts of the basin and intensifying aridization in the central-southern part (KST, KRN). Several extreme drought (1863, 1923, and 2003) and wet (1938) years with broad spatial extent were identified. Spectral analysis of the reconstructed series revealed significant cycles of approximately 2–5 years and 14–56 years. The results of this study demonstrate substantial spatial heterogeneity in drought dynamics and highlight the influence of both local and large‑scale climatic factors on moisture regimes in Baikal Asia.