ABSTRACT
The air mass frequency model uses Venn diagrams to distinguish three basic climatic regions, each determined by the relative dominance of air masses. Subsequently sub-regions are distinguished on the basis of air mass type. The monthly air mass dominance is determined from actual station surface data by comparison with a specially prepared plan of realms of dominant air mass regimes. A station marked by a seasonal regime would extend from one shaded area to another, whereas a plot of monthly data for a compound regime station might fall between all of the shaded realms. Simulation procedures were desirable to indicate the probable cloud cover conditions that might be anticipated in connection with a particular proposed mission. Careful pattern comparisons should then help to indicate more positively where and why the chief variations in climate occur. Armed with knowledge, considerable progress might then be made by workers seeking to extrapolate past trends into the future, to the enormous benefit of mankind.
