O3 profiles retrieved from limb scatter measurements:: Theory

An algorithm is presented for retrieving vertical profiles of O-3 concentration using measurements of UV and visible light scattered from the limb of the atmosphere. The UV measurements provide information about the O-3 profile in the upper and middle stratosphere, while only visible wavelengths are capable of probing the lower stratospheric O-3 profile. Sensitivity to the underlying scene reflectance is greatly reduced by normalizing measurements at a tangent height high in the atmosphere (similar to 55 km), and relating measurements taken at lower altitudes to this normalization point. To decrease the effect of scattering by optically thin aerosols/clouds that may be present in the field of view, these normalized measurements are then combined by pairing wavelengths with strong and weak O-3 absorption. Excluding pointing errors, we conclude that limb scatter can be used to measure O-3 between 15 km and 50 km with 2-3 km vertical resolution and better than 10% accuracy.