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- Author or Editor: Milton D. Shanklin x
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Abstract
More than three years of 3-hr high-contrast whole-sky photographs, sky-cover observations, and cloud-type observations were utilized to develop two methods for estimating cloud-free line-of-sight probabilities through the entire atmosphere for any desired geographical location. One method acquire a knowledge of the probability of each sky-cover category (tenths or eighths); the other method requires both sky-cover and cloud-type information.
Abstract
More than three years of 3-hr high-contrast whole-sky photographs, sky-cover observations, and cloud-type observations were utilized to develop two methods for estimating cloud-free line-of-sight probabilities through the entire atmosphere for any desired geographical location. One method acquire a knowledge of the probability of each sky-cover category (tenths or eighths); the other method requires both sky-cover and cloud-type information.
Abstract
Relative frequencies of cloud-free lines-of-sight were determined at specified elevation angles and directions by utilizing data from photographs taken with a camera with a 180° (fish-eye) lens and infrared film to produce high-quality photographs of the sky. Four summers of hourly daytime data were used to find relative frequencies as functions of viewing angle, sky cover, sunshine and cloud type. Persistence and recurrence relative frequencies, comparisons between “clear” and cloud-free lines-of-sight, and a general method for estimating probabilities of cloud-free lines-of-sight for any location are presented and discussed.
Abstract
Relative frequencies of cloud-free lines-of-sight were determined at specified elevation angles and directions by utilizing data from photographs taken with a camera with a 180° (fish-eye) lens and infrared film to produce high-quality photographs of the sky. Four summers of hourly daytime data were used to find relative frequencies as functions of viewing angle, sky cover, sunshine and cloud type. Persistence and recurrence relative frequencies, comparisons between “clear” and cloud-free lines-of-sight, and a general method for estimating probabilities of cloud-free lines-of-sight for any location are presented and discussed.
Abstract
Effects of sky cover variations on daylight total hemispheric radiation were determined from measurements made at Columbia, Mo. Total hemispheric radiation was measured by a Beckman and Whitley radiometer, solar radiation by an Eppley pyrheliometer, and sky cover by photoelectric scanning of whole-sky negatives. Regressions were calculated relating values of incoming radiation during daylight hours to sky cover. Daily total hemispheric radiation was expressed using values of sky cover and the amount of radiation received at the top of the atmosphere. Average hourly hemispheric and downward solar radiation received during daylight hours was expressed as functions of the second power of sky cover, except for large solar zenith angles. Decreases in total hemispheric radiation with increasing sky cover were attributed mainly to decreases in values of the incoming solar radiation component.
Abstract
Effects of sky cover variations on daylight total hemispheric radiation were determined from measurements made at Columbia, Mo. Total hemispheric radiation was measured by a Beckman and Whitley radiometer, solar radiation by an Eppley pyrheliometer, and sky cover by photoelectric scanning of whole-sky negatives. Regressions were calculated relating values of incoming radiation during daylight hours to sky cover. Daily total hemispheric radiation was expressed using values of sky cover and the amount of radiation received at the top of the atmosphere. Average hourly hemispheric and downward solar radiation received during daylight hours was expressed as functions of the second power of sky cover, except for large solar zenith angles. Decreases in total hemispheric radiation with increasing sky cover were attributed mainly to decreases in values of the incoming solar radiation component.
