Discussion of “Climatology since the year 1800”

Abstract

The writer would like to call attention to two more recent compilations of monthly mean cloudiness over the entire Earth which should be added to those listed under cloudiness.Brooks [1927] prepared monthly maps of mean cloudiness over the entire Earth (actually 90°N to 80° S) from which he computed values of mean cloudiness over the oceans and land masses by ten‐degree belts around the Earth. Although the original maps were not published, copies of the January and July maps may have been included in Simpson's [1929] classical paper, “The distribution of terrestrial radiation.” Simpson wrote: “The surface of the Earth between latitude 70° N and 70° S was divided into 10° squares, for each of which Brooks determined the mean temperature and the mean cloud amount for each of the two months, January and July. The values are shown on Figures 2, 3, 4, and 5.” Brooks' values of the mean monthly and annual cloudiness over the Earth derived from the original maps were published in the Memoirs of the Royal Meteorological Society [Brooks, 1927]. These values have been used extensively in computations of the albedo of the planet Earth, the distribution of terrestrial radiation, and the terrestrial heat balance. It is interesting to note that the maps which Leighly stated were apparently the latest compilations of mean cloudiness over the Earth (actually 80° N to the coast of Antarctica at approximately 70° S) and published in Shaw's Manual of Meteorology [Shaw, 1928; ed. 2, 1936], also were compiled by Brooks in 1919 and revised by him in 1921.