Some aircraft observations of fluxes of solar radiation in the atmosphere

Abstract

AbstractAn account is given of some recent observations of solar‐radiation fluxes from aircraft of the Meteorological Research Flight. This account consists of two parts: High‐level measurements of the albedo of the earth and atmosphere from a Canberra aircraft over southern England in 1958 and 1959, and over the Sahara Desert and Equatorial East Africa in June 1958 and January 1960. Observations from a Hastings aircraft of the absorption and reflection of total and visible solar radiation from a cloud‐free atmosphere over the English Channel. From (1), frequency distributions of observations within given albedo ranges have been extracted and correlation of albedo with the observed cloud cover attempted. The mean of albedo observations over southern England was 0·5 in 1958 and 0·3 in 1959; over the Sahara Desert about 0·3 and over Equatorial Africa about 0·2.The Hastings flights show that instantaneous heating rates in excess of 5°C/day at some level below 10,000 ft occur quite frequently. When allowance is made for heating due to absorption by the near infra‐red bands of water vapour and carbon dioxide (1‐2°C/day) it is found that the residual absorption does not depart significantly from greyness except in a few cases when the absorption appears to be concentrated in the near infra‐red.For the lowest levels, the absorption coefficient due to haze for total radiation is estimated to average about 20 per cent and for visible radiation about 5 per cent of the attenuation coefficient. Back‐scattered radiation accounts for about 5 per cent of the total attenuation.