The explanatory note gives the criteria used for the different desertification classes distinguished on the accompanying maps. The climate-aridity index maps was composed from calculations of net radiation from about 3,600 stations, using the Budyko ratio as criteria. An experimental world scheme of aridity and drought probability was compiled by Kovda and explained in a table giving 14 classes of aridity and drought probability, delineated on a world map.
1. Cover title: Map of the world distribution of arid regions : explanatory note.
- "The base map, at a scale of 1:25,000,000, has been obtained by photographical reduction of the 1:5,000,000 scale map of the world of the American Geographical Society of New York, and by a contraction of ocean areas. For the Americas, the bipolar oblique conformal projection has been used; elsewhere, the Miller stereographic projection, modified in three conformal zones and adopted for the FAO/​Unesco Soil map of the world in 16 sheets, has been utilized."
2. Accompanied by: Map of the world distribution of arid regions : explanatory note. (54 p. : ill. ; 27 cm.)