On the Global Balance of Water Vapor and the Hydrology of Deserts

An attempt is made to measure the horizontal divergence of the vertically integrated moisture flux over the northern hemisphere for the calendar year of 1950. This is done through the evaluation of daily data for some 90 upper air stations at several levels up to 500 mb. The final map obtained indicates strong maxima of divergence not only over certain oceanic regions, but also over three separate arid regions. Such a result implies an unexpectedly large excess of evaporation over precipitation in these latter areas, which must be balanced by convergence of liquid water on and below the ground surface, unless the year studied was rather completely different from normal, this not being so likely, however.