Mapping of high resolution nitrogen dioxide vertical column densities with the Airborne Prism EXperiment (APEX) imaging spectrometer over Zurich, Switzerland

In this study, we describe the NO₂ retrieval from the Airborne Prism EXperiment (APEX) imaging spectrometer and present first results from data acquired over Zurich, Switzerland. APEX is a new high performance imaging spectrometer allowing to map air pollution at an unprecedented resolution of about 50 m which highly benefits local air pollution assessments. NO₂ vertical columns are estimated following a well-established two-step approach, i.e., the differential optical absorption spectroscopy (DOAS) technique is used to obtain differential slant column densities (dSCD) which are subsequently converted to vertical column densities (VCD) by radiative transfer simulations. First results reveal very plausible distributions of NO₂, e.g., peak concentrations in a shopping area or around the airport. We finally evaluated APEX NO₂ maps with ground-based air quality measurements and found good correlations with R of 0.73.