A global study of satellite observations of clouds in the Tropics and their relationship with dew point temperatures

Abstract

Charts showing isopleths of long-term monthly mean dew points over the world at sea level between 75^o N and 65^oS have been prepared for the months January, April, July and October.  The isopleths on these charts between 30^oN and 30^oS have been compared with the isopleths of average cloudiness based on satellite observations of 2 years over the same range of latitudes.  It has been shown that the sea level dew point isopleths have a high correlation with the cloudiness gradients and the orientation of the isopleths of cloudiness in the tropics in the northern as well as the southern hemispheres.  A general examination has also been made of the isopleths of dew points over the northern hemisphere at the 850 and 700-mb levels as available in recent published literature for the months January and July.  It is has been found that the isopleths at the 850-mb level resemble those at sea level in regard to their orientation and thus resemble the isopleths of average cloudiness, although to a less satisfactory extent than the sea level patterns.  The patterns at the 700-mb level differ appreciably from those at the 850-mb level particularly north of 15^o N.  The significance of these factual findings and the possible usefulness of the dew point temperatures in studies of the moisture-field and the water-budget of the atmosphere are discussed.