Retrieval of NO2 vertical profiles from ground-based UV-visible measurements: Method and validation

Abstract

Vertical profiles of NO2 are retrieved from ground-based UV-visible slant columns by sequential estimation, using a forward model that consists of a stacked box photochemical model and a radiative transfer model. The retrieval method is characterized, and a rigorous error analysis is presented. The vertical resolution of the retrieved profiles is shown to vary from 5 to 10 km, depending on the retrieval altitude. The retrieved profiles are found to be moderately sensitive to the assumed vertical profiles of ozone and aerosol, to the range of solar zenith angles of the observations, and to the error in the slant column. However, in the altitude range 10 to 35 km they are relatively insensitive to a priori information and agreed well with profiles from simultaneous balloon-borne measurements.