Some features of the structure of the tropical tropopause

Statistics of the minimum saturation humidity mixing ratio are extracted from 2 500 radiosonde ascents in the tropics (10°N to 10°S) and in the region of the Asian summer monsoon. Two periods of approximately 20 days are examined, one in the northern winter and one in the northern summer. The relation of the observations to an hypothesis, proposed by A. W. Brewer in 1949, of mass exchange between troposphere and stratosphere is briefly discussed.