Orographic Cloud over the Eastern Slopes of Mauna Loa Volcano, Hawaii, Related to Insolation and Wind

Abstract

During the period 1?11 June 1978, solar radiation and other meteorological data were gathered at eight stations arranged in a nearly linear transaction extending from the coast at Hilo, Hawaii to Mauna Loa Observatory, 60 km inland and 3400 m higher. Solar radiation distributions followed climatological rainfall patterns; the driest areas were sunniest. At the wettest sites, underneath the orographic cloud, measured global solar radiation was only 50% of clear-sky potential, and the diffuse component probably accounted for more than 50% of the global radiation. The orographic cloud developed during the day in upslope winds, and sharply reduced afternoon solar radiation at all sites. Total cloudiness, and hence insulation, varied greatly from day to day due to the passage of trade wind cloud masses and jet stream cirrus.