The Madrid Intercomparison of Nitrogen Dioxide Measuring Instruments (MINDI)
Van Roozendael, Michel¹; Gil, Manuel²; Puentedura, Olga²; Hendrick, François¹; Tack, Frederik¹; Richter, Andreas³; Wagner, Thomas⁴; Piters, Ankie⁵; Saiz-Lopez, Alfonso⁶; Bojkov, Bojan⁷; Fehr, Thorsten^7
1Belgian Institute for Space Aeronomy, BELGIUM; ²Instituto Nacional de Tecnica Aeroespacial, SPAIN; ³University of Bremen, GERMANY; ⁴Max Planck Institute for Chemistry, Mainz, GERMANY; ⁵Royal Netherlands Meteorological Institute, NETHERLANDS; ⁶6. CIAC-CSIC, Laboratory for Atmospheric and Climate Science, SPAIN; ⁷ESA/ESRIN, ITALY

Air quality is an important theme within the Copernicus Global Monitoring of Environment and Security (GMES) programme, which aims at developing operational services addressing key environmental issues of importance for the European citizen. The observational space component is developed by ESA as part of the Sentinel programme. In particular Sentinels 4 and 5 are dedicated to atmospheric composition monitoring. However the first atmospheric Sentinel will be Sentinel 5 Precursor (S5-P), a mission scheduled for launch already in 2015. Having on board the Dutch/ESA TROPOMI instrument, S5P will provide global observations of a number of atmospheric pollutants (NO2, HCHO, SO2, O3, CO) with an unprecedented spatial resolution of 7x7 km2 adequate to resolve emissions at the city-scale. The validation of S5-P (and the subsequent Sentinels 4 and 5) trace gas column data products requires the development of adequate ground-truth instrumentation. Remote-sensing Max-DOAS instruments are well suited to this aim, however the current network of instruments is too sparse and lack homogeneity as well as a proper accuracy characterization. To address this issue, a large-scale intercomparison campaign (CINDI) was organised in Cabauw, The Netherlands during summer 2009, with a focus on nitrogen dioxide measurements. Important lessons were learned and significant progress made regarding instrumentation and data analysis. This success now calls for a follow up intercomparison exercise addressing unresolved issues on data harmonisation and interpretation of measurements. In particular, a major uncertainty for the satellite validation is coming from the temporal and spatial gradients, which are typical for short-lived trace gases with localised sources.
We present the plans for the Madrid Intercomparison of Nitrogen Dioxide measuring Instruments (MINDI). This campaign will be hosted in the INTA facilities nearby Madrid. Multiple ground-based remote-sensing and in-situ instruments will be deployed at and in the vicinity of the INTA site, and complemented by balloon measurements providing high resolution NO2 vertical profiles. In addition, the INTA research aircraft will be equipped with a nadir imaging instrument allowing for NO2 column mapping at the local (satellite sub-pixel) scale.