Weather and Solar Radiation Reception in the Equatorial Trough

Abstract

Canton Island (2°49?S, 171°41?W) was selected to study equatorial trough weather conditions and their effects on incoming solar radiation. The chosen study period, July 1957?June 1958, was quite appropriate since the mean position of the trough for this year was about 4° south of its mean annual position and it frequently affected Canton. Cloud distribution, moist layer thickness, precipitable water content and weather conditions in the equatorial trough zone (out to 10° on either side of the trough axis) are discussed. Incoming solar radiation is considered in relation to opaque sky cover since the total sky cover often included an excessively large thin cirriform contribution which did not significantly reduce incoming solar radiation. In the vicinity (within 3°) of the trough axis only one out of five days was affected by disturbance type weather (extensive cloud cover and precipitation). In these disturbance cases, for an overall average, 34.6% of the solar radiation on a horizontal surface at the top of the atmosphere penetrated through to the earth's surface. For fair weather cases 61.3% penetrated through to the earth's surface.