Anomalous Orographic Rains of O'ahu (Hawai'i) Revisited: An Over-sea Origin Indicated

摘要

The first study of anomalous orographic rains of O'ahu, Hawai'i,utilized the average daily amounts and shower frequency characteristics as anindication of where they were first formed. In this renewed study I show that therain rates, rather than the amounts and shower frequency, are more appropriatefor revealing rain origin. Hourly amounts at gage sites alined about parallel andnormal to the winds are graphically presented. The graphs reveal that many ofthe rains, although concentrated over the island, apparently originated as lightrains over the windward sea along a crosswind line, intensifying as thewind-borne overcast of cumulus clouds was carried inland. This finding addsfurther support to early suggestions of an over-sea origin of many of O'ahu'sorographic rains. It is hypothesized that all of these anomalous rain lines, andperhaps the trade-wind cumulus showers as well, originate upwind of the island.The idea could be readily tested experimentally.