Sea-Surface Cooling After TRMM-Defined Heavy-Rain Records in the South China Sea: Geographic-Seasonal Heterogeneity and Scale-Dependent Limits

Heavy rainfall records over the South China Sea accompanies weather systems that can also alter sea-surface temperature (SST), but the magnitude, heterogeneity, and scale dependence of the associated post-event cooling remain unclear. Using 1,192,517 TRMM-defined heavy-rain grid-cell/day records and matched same-grid, same-calendar-month controls during 1998–2015, we quantified the 1–3–day post-event SST contrast and examined rainfall–SST correspondence at daily, monthly, and pooled spatial resolutions. The mean event-minus-control contrast was −0.228 °C (cross-year sensitivity interval: −0.243 to −0.214 °C). Cooling varied geographically, from −0.427 °C at Dongsha to −0.169 °C at Nansha, and seasonally, from −0.315 °C in March–April to −0.130 °C in December–February. Same-grid overlap between SST-response and heavy-rain records was weak on the exact date (F1 = 0.059) and remained limited within ±2 days (F1 = 0.276). Across 216 held-out months in reciprocal temporal folds, basin-wide monthly TRMM heavy-rain counts and weighted SST-response record equivalents co-varied strongly (r = 0.854), whereas their de-seasonalized anomalies were only weakly associated (r = 0.197). Pooled January and July maps retained broad spatial structure after combining 18 held-out instances. Because atmospheric and oceanic covariates were not controlled, the SST contrast represents a conditional association rather than an isolated rainfall effect. These findings identify geographically and seasonally heterogeneous post-event cooling, while showing that strong correspondence in aggregated diagnostics largely reflects shared seasonal structure rather than daily record-level or monthly anomaly agreement.