The vertical distribution of tritium in water vapor in the lower troposphere

A series of 16 aircraft soundings was made during the summers of 1966 and 1967 to measure the vertical distribution of tritium in water vapor from the surface to an altitude of 5 km. Three types of tritium distributions were found. The type I soundings showed a generally increasing tritium concentration with increasing height. Type II soundings were characterized by a constant tritium concentration with increasing altitude. On type III soundings the tritium concentration gradually decreased to approximately 2.4 km and then abruptly increased. These soundings are discussed in terms of the origin of the air masses, evapotranspiration, and the water vapor mixing ratio.