Cloud cover Cloud cover Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds when observed from a particular location. Okta is the usual unit of measurement of the cloud cover. The cloud cover is correlated to the sunshine duration as the least cloudy locales are the sunniest ones while the cloudiest areas are the least sunny places. The global cloud cover averages around 0.68 when analyzing clouds with optical depth larger than 0.1. This value is lower (0.56) when considering clouds with an optical depth larger than 2, and higher when
History of measurement to use their customary units. Among the numerous customary systems, many have been adapted to become an integer multiple of a related metric unit: The Scandinavian mile is now defined as 10 km, the Chinese jin is now defined as 0.5 kg, and the Dutch ons is now defined as 100 g. The American system is unusual in that its units have not been adapted in such a manner. History of measurement The earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction,