Photoelectric measurements of the seasonal variations in daylight at Plymouth from 1947 to 1949

✍ Scribed by W. R. G. Atkins; Pamela G. Jenkins

• Publisher: John Wiley and Sons
• Year: 1952
• Tongue: English
• Weight: 386 KB
• Volume: 78
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49707833509

✦ Synopsis

Abstract

Daylight received on a horizontal surface has been measured for fourteen years using a Burt vacuum sodium cell and Cambridge thread‐recorder galvanometer. Mean monthly values of daily maxima, in kilolux, are tabulated, also mean monthly values of illumination in kilolux hours. These are compared with similar measurements at Kew in 1947 and 1948, obtained using a selenium cell. The kilolux hours for each month are shown as a percentage of individual years, with mean values for fourteen years and percentage range for variation. Annual totals were 108, 124 and 122 megalux hours for 1947, 1948 and 1949 respectively with 116 as the mean of the whole series. Between these and sunshine or rainfall there is no simple relation. Cloudless days are not the brightest owing to downward reflection from clouds. Darkest days in each month commonly show 17 to 40 per cent as many kilolux hours as do brightest, though smoke pollution may reduce illumination to 5 per cent.