Towards tomographical MAX DOAS profile retrieval: sensitivity studies

The ground-based Multiple Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurement technique is of high interest to measure local scale pollution events like trace gas plumes above cities or power plants. Besides vertical column densities and especially for the comparison with in-situ measurements and model simulations, vertical profiles of aerosol extinction and trace gas concentrations are retrieved. In this the horizontal extent of the plume is usually neglected in the forward modelling (i.e. horizontally homogeneous distribution is assumed).

Here we investigate by sensitivity studies on simulated measurements 1) the systematic errors induced when in fact a horizontally limited plume is measured while neglecting the limited horizontal  plume extent in the retrieval, 2) the capabilities to correct for these errors by a tomographic measurement scheme scanning the same air masses by two instruments, and 3) we provide an outlook to the practical applicability of such a measurement concept.