Measurements of solar occultation - The error in a naive retrieval if the constituent's concentration changes

The stratospheric concentrations of many minor constituents change rapidly at sunrise or sunset. If this happens, there is an inherent error when retrieving the vertical profiles of the constituents from measurements of their absorption of sunlight. For retrievals of NO at sunset the error can be estimated from in situ measurements alone, without appeal to a model of stratospheric photochemistry. Below 20 km this error can approach 100 percent, so that the retrieved NO is zero. But at 40 km, and at 25 km when the absorption is strong and Lorentzian, it can be less than 20 percent. Precise calculations of the error, even if small, require model calculations of the sunset and sunrise changes. Using a model, the error for NO, NO2, OH, and ClO has been calculated.