Turnover times of¹³⁷Cs and HTO in the troposphere and removal rates of natural aerosol particles and water vapor

The average vertical fluxes 〈J〉 of 137Cs and HTO between 40° and 50°N are calculated from the mixing ratio profiles in the upper troposphere and from the surface deposition. During spring 1966, 〈JCs〉 = 0.67 127Cs atoms/cm2 sec and 〈JT〉 = 51 HTO molecules/cm2 sec. From these fluxes and from the vertical profiles of the mixing ratio the turnover times are estimated as a function of altitude. These times increase from a few days in the surface layer to 20 days for HTO and 30 days for 137Cs at the tropopause. It is, shown that the turnover times and their altitude dependence should hold approximately for all seasons between 30° and 50°N. The tracer turnover times can be interpreted as removal times of natural aerosol particles and water vapor. In particular, they can be used to estimate the removal times of water vapor and aerosols injected by commercial aircraft in the upper troposphere.