Simultaneous occurrence of different cloud types.

Abstract

Cloud observations from land stations and from ships in the ocean are used to investigate the frequency of observation and the co-occurrence of different cloud types, and the geographical and seasonal variations of these co-occurrences. Ground-based observations are used because they provide a more definitive identification of clouds by type than do satellite observations. It is found that, on the average at all latitudes and in all seasons, clear skies occur more frequently, by a factor of about 4, over land than over the oceans; cumulus occurs twice as frequently over the oceans than over land but cirrus is reported with a somewhat higher frequency over land. -from Authors