Inversion technique to obtain height profiles of ammonia

The measurements of the minor constituents in the atmosphere are of great significance to understand the radiation budget, chemistry and dynamics of the atmosphere in connection with global change. Ammonia is one of such gases in the atmosphere and is most poorly understood and difficult to measure. Ammonia plays an important role in determining the rate of formation of sulfate aerosols. The laser heterodyne spectrometer has the capability of measuring the vertical profiles of ammonia. In view of the above inversion technique based on inverse solution of radiative transfer equation has been used below 25 km while Voigt line profile has been used above 25 km where Doppler broadening is dominant. A large number of channels, one at line centre and others in the wing of the line were chosen to resolve the line to get good height resolution. The spectral intensity at these channels was computed using model profile. A uniform vertical distribution of ammonia was assumed to invert the computed spectral intensity on these channels. In the present communication the inversion technique developed to retrieve the vertical profiles will be discussed in detail.