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Changes in Hawaiian Island Precipitation Extremes, 1950-2007

Reference
Chu, P.-S., Chen,Y. R. and Schroeder, T. A. 2010. Changes in precipitation extremes in the Hawaiian Islands in a warming climate. Journal of Climate 23: 4881-4900.
Authors Chu et al. (2010) examined five climate change indices related to extreme precipitation events in the Hawaiian Islands based on daily observational records over a period 1950-2007. The five indices were (1) simple daily intensity index, (2) total number of days with precipitation exceeding 25.4 mm( 1 inch), (3) annual maximum consecutive five-day precipitation amount, (4) the fraction of annual total precipitation from events exceeding a threshold value and, (5) the consecutive number of dry days. These five indices were examined in detail for two time periods (1950-79 and 1980-2007) in an effort to determine how recent warming may have changed the precipitation characteristics over the Hawaiian Islands.

Results indicated, according to the authors, that "there has been a change in the type of precipitation intensity since 1980, resulting in more frequent light precipitation and less frequent moderate and heavy precipitation intensity." The study further showed that the Hawaiian Islands in recent years have experienced shorter annual number of days with intense precipitation, smaller consecutive five-day precipitation amounts and a lengthening of annual maximum number of consecutive dry days. The study also found that ENSO (El Niño-Southern Oscillation) dominates Hawaiian Islands precipitation patterns, with the La Niña (cold) phase providing more extreme precipitation events.

It is of interest to compare the findings of this study with model projections that suggest a warmer climate provides more moisture in the atmosphere and will result in more frequent and intense precipitation events. Yet, as the results of this study show, the availability of more moisture in the atmosphere does not necessarily produce more extreme (heavy) rainfall, which suggests that the models still have a long way to go before they get it right.

Archived 9 May 2012