Century-long rainfall structure in Macao: Implications for urban governance
Long-term climate records provide a historical evidence base for governing urban weather-related hazards. This study uses monthly total rainfall and monthly rainy-day records for Macao from 1901 to 2000 to construct a structured monthly panel. It descriptively examines annual totals, annual rainy days, rainfall per rainy day, the April–September wet-season share, monthly and seasonal patterns, 20-year subperiods, extreme years, and the data-quality boundaries of the published historical compilation. Among 97 years with complete monthly records, the mean annual rainfall was 1,879.3 mm (standard deviation: 454.3 mm). Annual rainfall showed a significant positive trend (ordinary least-squares slope, 6.24 mm/year; Theil–Sen slope, 6.61 mm/year), and annual rainy days also increased (0.36 days/year). Heteroscedasticity- and autocorrelation-consistent inference did not alter these substantive conclusions. By contrast, the linear trend in annual rainfall per rainy day was not statistically significant. Rainfall remained concentrated in late spring, summer, and early autumn: based on monthly climatology, April–September accounted for 82.9% of annual rainfall, while summer and spring accounted for 47.5% and 28.8%, respectively. For the shared 1961–2000 period, annual rainfall covaried strongly with the published Hong Kong Observatory record (Pearson r = 0.859; p < 0.001). These results support a seasonally differentiated maintenance calendar, tail-year scenario preparation, and a staged data architecture linking historical rainfall with real-time hydrometeorological, water-system, and service-impact records.
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