Measurements of stratospheric chlorine monoxide (ClO) from groundbased FTIR observations

Stratospheric chlorine monoxide was measured at a site near sea level at Aberdeen, UK, using ground-based Fourier-transform infrared (FTIR) spectroscopy. Measurements were made based on the identification of 13 ClO adsorption lines. The instrumentation is described. The ClO column was measured at 3.42 10 super(15) molecules/cm super(2), which was consistent with very high ClO mixing ratios in the lower stratosphere. These high levels were related to significant ozone depletion. The total inorganic Cl column, when summed from the concentrations of ClO, hydrogen chloride, and ClONO sub(2), was found to be lower than that estimated from previous ground-based infrared measurements.