A novel framework for decoding long-distance climate–monsoon interactions: the Greater Himalayas

Although the Greater Himalayas are a critical hydroclimatic zone supporting South Asia's water supplies, the mechanisms linking monsoon rainfall to major climate drivers remain insufficiently understood. The investigation revealed two distinct seasonal signals: a pre-monsoon (March–May; MAM) wetting tendency (+0.582 mm/year), contrasting with strong monsoon (June–September; JJAS) drying (−0.976 mm/year) and post-monsoon (October–December; OND) decline (−0.381 mm/year). Correlation results indicate that the South Asian Summer Monsoon Index (SASMI; ρ = 0.332) influences Himalayan precipitation more strongly than the Indian Summer Monsoon Index (ISMI; ρ = 0.310), with substantial lagged effects from El Niño-Southern Oscillation (ENSO; ρ = −0.267) and the Indian Ocean Dipole (IOD; ρ = 0.241). Empirical Orthogonal Function (EOF) analysis identified three leading rainfall modes linked to ISMI, SASMI–ENSO, and orographic control, explaining 74.6% of variance. Wavelet Coherence (WTC) further reveals dynamic, non-stationary relationships, particularly the declining ISMI-rainfall association after the 1970s.