Changes in Precipitation Extremes in the Hawaiian Islands in a Warming Climate

发布时间：2013-12-27 14:39:39

Changes in Precipitation Extremes in the Hawaiian Islands in a Warming Climate P AO-S HIN C HU,Y ING R UAN C HEN,AND T HOMAS A.S CHROEDER Department of Meteorology,School of Ocean and Earth Science and Technology,University of Hawaii at Manoa,Honolulu,Hawaii(Manuscript received23October2009,infinal form29April2010)ABSTRACTFor thefirst time,trends offive climate change indices related to extreme precipitation events in theHawaiian Islands are investigated using daily observational records from the1950s to2007.Four indices[simpledaily intensity index(SDII),total number of day with precipitation$25.4mm(R25),annual maximumconsecutive5-day precipitation amount(R5d),and the fraction of annual total precipitation from eventsexceeding the1961–9095th percentile(R95p)]describe the intensity(SDII),frequency(R25),and magnitude(R5d and R95p)of precipitation extremes,and thefifth index[consecutive dry days(CDD)]describesdrought conditions.The annual probability density functions(PDFs)of precipitation indices for two epochs(i.e.,1950–79and1980–2007)are analyzed.Since the1980s,there has been a change in the types of pre-cipitation intensity,resulting in more frequent light precipitation and less frequent moderate and heavyprecipitation intensity.The other three precipitation-related indices(R25,R5d,and R95p)demonstratea shift toward the left of the distribution over time,suggesting shorter annual number of days with intenseprecipitation and smaller consecutive5-day precipitation amounts and smaller fraction of annual pre-cipitation due to events exceeding the1961–9095th percentile in the recent epoch relative to thefirst epoch.The changes of PDF distribution for SDII,R25,R5d,and CDD are significant at the5%level according toa two-sample Kolmogorov–Smirnov test.A nonparametric trend analysis is then performed for four periods,with different starting years(e.g.,the1950s,the1960s)but the same ending year(2007).Long-term downward trends are evident for fourprecipitation-related indices,and long-term upward trends are observed for CDD.Geographically,Kauai andOahu are dominated by long-term decreasing trends for four precipitation-related indices,while increasingtrends play the major role over the island of Hawaii.The upward trends of drought conditions in the long runare predominant on all the major Hawaiian Islands.To investigate whether the trends are stable throughout the time,the derivatives of trends for each of the30-yr running series are calculated(e.g.,1950–79,1951–80,...,1978–2007)for four precipitation-relatedindices at each station.For Kauai and Oahu,positive derivatives prevail for all indices in the presence of long-term negative trends,suggestive of a phase change in precipitation extremes and such extremes showing anupswing recently.For the island of Hawaii,there is also an indication of phase reversal over the last60yr,withnegative derivatives occurring in the presence of the background positive trends.A positive relationship is found between the precipitation indices and the Southern Oscillation index(SOI),implying more precipitation extremes during La Nin˜a years and vice versa for El Nin˜o years.Spatial pat-terns of standardized anomalies of indices are presented for the La Nin˜a/2PDO minus El Nin˜o/1PDOcomposites.1.IntroductionIt is well known that earth is undergoing an unprece-dented warming process since the Industrial Revolution. According to the Fourth Assessment Report(AR4)of the Intergovernmental Panel on Climate Change(IPCC; Solomon et al.2007),the rate of the global average surface temperature increased by0.0748C60.0188C decade21over the past100yr(1906–2005).Since1981, the rate of warming is faster,with a value of approxi-mately0.1778C60.0528C decade21.Consistent with the global warming trend,Hawaii temperature experienced an upward trend as well(Giambelluca et al.2008): 0.0438C decade21for the period of1919–2006and 0.1638C decade21for the past30yr.Corresponding author address:Pao-Shin Chu,Department ofMeteorology,School of Ocean and Earth Science and Technology,University of Hawaii at Manoa,Honolulu,HI96822.E-mail:chu@hawaii.edu15S EPTEMBER2010C H U E T A L.4881DOI:10.1175/2010JCLI3484.1Ó2010American Meteorological Society

Changes in Precipitation Extremes in the Hawaiian Islands in a Warming Climate

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