Stratospheric Water Vapor Variability for Washington, DC/Boulder, CO: 1964–82

Measurements for Washington, DC and Boulder, CO are combined to provide a time series of midlatitude stratospheric water vapor data for the period 1964–82. The mean concentration for the data period is shown to be nearly constant with altitude for the low stratospheric layer between 16–22 km with a mass mixing ratio for the layer of 2.5–2.6 ppmm. Above 22 km the mixing ratio increase slightly with altitude. Evident in the 60 mb level time series is an annual cycle, a quasi-biennial cycle and a long-term nonlinear trend. The quasi-biennial cycle in water vapor at midlatitudes is consistent with variations in tropical stratosphere zonal winds and temperature and total ozone and suggests a modulation of the Hadley cell circulation. The long-term trend shows mixing ratio increasing during the 1960s and decreasing in the 1970s after 1972.