Abstract
<jats:p>Abstract. The 247-year Seoul precipitation record (1778–2024), comprising 130 years of daily Chugugi rain-gauge measurements (1778–1907; Lee et al., 2024) extended by modern instrumental observations (KMA station 108, 1908–2024), constitutes the longest pre-industrial daily rainfall record in the world. Here we exploit this archive to test whether the circumglobal-teleconnection (CGT) mechanism that has been proposed to connect tropical volcanic eruptions to East Asian monsoon drought (Nie et al., 2026) imprints detectably on Seoul summer (JJA) rainfall. We apply Superposed Epoch Analysis (SEA) over 9 major eruptions (1783 Laki through 2022 Hunga Tonga) with 5,000-sample Monte Carlo bootstrap significance, continuous Morlet wavelet spectral analysis with AR(1) red-noise testing, and extended wavelet coherence between annual global VEI ≥ 4 eruption counts and Seoul JJA rainfall over 1830–2024 (N = 195). Three findings emerge. (i) The composite SEA shows no statistically significant post-eruption rainfall response at any lag from 0 to +7 yr (composite tropical-only –65 mm to +76 mm across the window; p > 0.45 at every post-eruption lag). Individual eruptions divide roughly equally between wet and dry post-eruption responses: Tambora (+298 mm), Krakatau (+132 mm), Agung (+267 mm), and Katmai (+58 mm) show net-wet years +1 to +3, while Cosiguina (–245 mm), Santa Maria (–109 mm), El Chichón (–153 mm), Pinatubo (–184 mm), and Laki (–152 mm) show net-dry. (ii) Wavelet spectral analysis reveals two significant decadal-to-multidecadal modes above the AR(1) red-noise null: a quasi-40-yr Pacific mode and a quasi-60-yr Pacific decadal mode. The interannual ENSO-like band (3–5 yr) does not exceed the null at the global-spectrum level, and the AR(1) coefficient of detrended JJA rainfall is essentially zero (−0.026), substantially weaker than previously assumed for monsoon precipitation series. (iii) Time-frequency wavelet coherence between volcanism and Seoul rainfall does not exceed the 95 % AR(1) null at any period. We do detect a modest patch of elevated coherence in the 8–16 yr band around 1900–1915 (Santa Maria–Katmai era), but no analogous patch around the recent Pinatubo–Hunga Tonga era. These findings constitute a constraint, not a confirmation: even the longest pre-industrial daily precipitation record in the world is insufficient to attribute a CGT-consistent volcanic monsoon signal at an individual mid-latitude site. We interpret this as evidence that volcanic forcing, where present in Seoul rainfall, is overwhelmed by background ENSO and Pacific-decadal variability, with event-to-event response heterogeneity likely reflecting eruption-specific stratospheric loading and background-state conditioning. The Seoul record nonetheless complements gridded paleoclimate proxies (MADA v2, RAP) by anchoring them with high temporal fidelity at a single mid-latitude site where East Asian monsoon and putative volcanic teleconnections converge.</jats:p>