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Item Description Ekern, Paul C. en_US 2008-10-16T01:20:49Z 2008-10-16T01:20:49Z 1993-08 en_US
dc.identifier.citation Ekern PC. 1993. Evaporation along a transect across southern Oahu, Hawaii. Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC project report, 94-01. en_US
dc.description.abstract Near O'ahu the annual oceanic evaporation is 65 in. (1651 mm) and the rainfall is 18 in. (457.2 mm), giving a 47-in. (1 193.8-mm) deficit. In 1981, evaporation over central O'ahu was 27 in. (685.8 mm) and rainfall was 197 in. (5 003.8 mm), for a 170-in. (4 318-mm) surplus. The pattern of evaporation over an island differs from that over the open ocean, just as the pattern of rainfall and cloudiness is changed by island topography. Evaporation measurements that were begun in 1980 at five leeward sites were expanded to include measurements at four windward sites in southern O'ahu from October 1985 through September 1987. Specially designed small rain-shielded evaporimeters were calibrated against class A pan evaporation. Such pertinent factors as rainfall, sunlight, wind, and air temperature were recorded for correlation with evaporation. Although monthly class A pan evaporation was 0.53 the evaporimeter measurement for the entire 1980-1987 period, a 0.55 ratio was finally adopted as a more reliable transformation value. Correlation coefficients of determination (r^2) values between monthly evaporimeter and pan evaporation readings ranged from 0.77 to 1.0, between pan evaporation and sunlight readings from 0.79 to 0.87, and between evaporimeter and sunlight readings from 0.66 to 0.93. A fivefold increase in pan level wind across the transect only increased the sunlight energy used as latent heat by 50%. Evaporation relative to the Manoa Mauka campus calibration site ranged from 0.79 on the windward coast, to 0.56 at the windward base of the Ko'olau Range, to 0.65 at the leeward base, to 1.2 at the extreme leeward site. Evaporation equivalent to 0.91 the windward net radiation but 1.23 the leeward value suggests negative advection onshore from the ocean and strong positive advection from the dry leeward surroundings. The annual water balance for October 1985 through September 1987 was a deficit of 20.4 to 32.4 in. (518.2 to 823.0 mm) at the windward coast, a surplus of 37.9 in. (962.7 mm) at the windward Ko'olau base, a surplus of 100 in. (2 540 mm) at the leeward Ko'olau base, and a deficit of 55.9 in. (1419.9 mm) at the leeward valley floor. en_US
dc.description.sponsorship Board of Water Supply City and County of Honolulu Grant/Contract No. C12355 en_US
dc.format.extent x + 23 pages en_US
dc.language.iso en-US en_US
dc.publisher Water Resources Research Center, University of Hawaii at Manoa en_US
dc.relation.ispartofseries WRRC Project Reports en_US
dc.relation.ispartofseries 94-01 en_US
dc.subject evapotranspiration en_US
dc.subject evaporimeters en_US
dc.subject pan evaporation en_US
dc.subject rainfall en_US
dc.subject water balance en_US
dc.subject sunlight en_US
dc.subject transect en_US
dc.subject southern Oahu en_US
dc.subject Hawaii en_US
dc.subject.lcsh Evaporation (Meteorology) -- Hawaii -- Oahu. en_US
dc.title WRRCPR No.94-01 Evaporation Along A Transect Across Southern Oahu, Hawaii en_US
dc.type Report en_US
dc.type.dcmi Text en_US

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