The Climatology of Relative Humidity in the Atmosphere

Abstract The present paper deals with the analysis of the time-average relative humidity fields in the atmosphere. Twice-daily estimates of relative humidity are used. After some theoretical considerations on the relations between relative humidity, other moisture parameters, and temperature, a critical analysis of the various sources of data is made considering their possible limitations. Various methods of computing relative humidity are formulated and discussed. The global distribution of relative humidity at various levels shows that it is not zonally uniform with centers of various intensities at all latitudes. The global maps show maxima in the equatorial zone and minima in the dry subtropical belts around 30°N and 30°S. The land–sea contrast and variations related to the orographic relief are also apparent. The general pattern of relative humidity is similar at all levels but its magnitude decreases with altitude. The seasonal analyses show a similar pattern as the annual analyses but are slightly ...