Measurement of the greenhouse radiation associated with CCl4

One of the gases which potentially can interfere with the remote sensing of gases of military interest is carbon tetrachloride (CCl4). Carbon tetrachloride is also a strong greenhouse gas with a global warming potential of 4,000. Ground-based, thermal emission measurements of the cold, clear sky have been made showing the v(3) fundamental emission band of carbon tetrachloride (CCl4) which is located in the 786806 cm(-1) region. A spectrum of the non-CCl4 background emission features has been simulated using the FASCD3P line-by-line radiation code with measured radiosonde parameters of pressure, temperature and humidity. The simulated spectrum has been used to extract the CCl4 thermal emission band from the atmospheric emission spectrum. Tropospheric CCl4 mixing ratios of 120+/-20 in 1995 and 135+/-10 pptv in 2003 were determined from these measurements. In addition, the downward long-wave flux associated with the v(3) emission band of CCl4 measured at the surface has been estimated to be 0.046 W/m(2) +/- 17%. This flux is about one third and one fifth of that corresponding to the chlorofluorocarbons CFC-11 and CFC-12, respectively.