Based on thunderstorm day observations from 39 stations across the Tibetan Plateau (TP) during 1979-2013, this study examines interannual-to-decadal variability in summer thunderstorm days and their connections with atmospheric circulations and TP thermal-dynamic conditions. Empirical Orthogonal Function (EOF) and wavelet analyses identify two dominant patterns: The first leading EOF mode features a northeast-southwest dipole pattern with persistent positive anomalies over the northeastern TP, exhibiting 3-5-year and 8-year periodicities. The second leading mode presents a southwest-northeast dipole pattern with pronounced positive anomalies in the southwestern TP, characterized by 3- and 5-year oscillations. Enhanced interannual thunderstorm variability post-2000 underscores growing climate risks for regional disaster management. Further analyses reveal that the South Asian High (SAH) serves as a crucial circulation system on interannual thunderstorm day variability. The Indian Ocean Basin-wide (IOBW) mode and the upper-level (100hPa) thermal forcing over the TP are connected to thunderstorm days through SAH and low-level divergence. Convective Available Potential Energy (CAPE) also emerges as an important factor, with enhanced CAPE values significantly increasing thunderstorm day frequency. Multiple-variable regression analyses indicate that IOBW and CAPE collectively explain 52.1% of the interannual thunderstorm day variability (TP heating excluded from the final model). CAPE demonstrates greater relative importance (standardized regression coefficient: 0.68) compared to IOBW (coefficient: 0.31). These findings advance the understanding of mechanisms underlying TP interannual thunderstorm activity and provide critical insights for improving regional climate projections.
 

Tibetan Plateau; Thunderstorm Day; Large Interannual Variability; IOBW; CAPE