Ozone profiling with UV and visible limb scatter data

Here we present an algorithm for retrieving ozone vertical concentration profiles using measurements of UV and visible light scattered from the limb of the atmosphere. Recently this technique was demonstrated in the 50-15 km region with data from the Shuttle Ozone Limb Sounding Experiment (SOLSE) and the Limb Ozone Retrieval Experiment (LORE), which was flown on STS-87 in Nov. 1997. In addition, the capability to take such measurements will be realized in the next few years by SAGE III, SCIAMACHY and ODIN/OSIRIS, as well as on the next generation of NOAA's polar orbiters by the Ozone Mapping and Profiler Suite (OMPS/NPOESS).

The UV measurements provide information about the ozone profile in the upper and middle stratosphere. Since the Rayleigh scattering optical depth can be quite significant for the uv channels, only visible wavelengths are capable of probing the lower stratospheric ozone profile. Calculations of the instrument pointing for the STS-87 data are done with images taken near 345 nm. Sensitivity to the underlying scene reflectance is greatly reduced by using measurements at a tangent height high in the atmosphere (50 km for the uv channels) as a normalization, and ratioing measurements taken at lower altitudes to this normalization point. These normalized measurements are then combined by pairing a wavelength where ozone absorbs strongly with one having weak absorption by ozone. For the visible channels, a triplet is used (525, 600, and 675 nm) to reduce the effect of stratospheric aerosol scattering. The presentation will include both a discussion of the sensitivity of the retrieval to the assumptions made and results from the STS-87 flight showing that this technique can successfully measure ozone down to at least 15 km with 3 km vertical resolution.