Use of Differential Optical Spectroscopy for Satellite Diagnostics of Methane Content in a Scattering Atmosphere

The application of differential optical absorption spectroscopy (DOAS) for the diagnostics of localized methane emission based on data from satellite spectral measurements is discussed. It is shown that the application of DOAS in a scattering atmosphere can lead to significant errors in estimates of the concentration of methane. It is proposed that it be supplemented by a filtering procedure for signals distorted by atmospheric scattering effects which takes into account the correlation of the errors in the recovered concentrations of methane and water vapor owing to the uncertainty in the trajectory of the photons propagating in a scattering atmosphere. This correlation has been estimated by numerical calculations of these errors for a model atmosphere that includes cirrus clouds and two types of surface aerosols.