The AROMAPEX campaign was carried out in April 2016 in Berlin. The scientific team involved in the project includes researchers from Germany (FUB, University of Bremen, DLR, MPIC), Belgium (BIRA, VITO), Netherlands (KNMI, TNO, TU Delft) and Romania (INCAS, UGAL).
The primary objective of the AROMAPEX experiment was the inter-comparison of APEX and AirMap; two airborne imagers dedicated to tropospheric NO2, a major air pollutant in urban areas and a key species in tropospheric chemistry. The airborne imagers were operated from two planes: APEX was on board DLR's Do-228-112 D-CFFU and AirMAP on board the FUB Cessna C-207D-EAFU (Fig. 1).
Fig 1. The DLR Dornier (D-CFFU) and the FUB Cessna (D-EAFU) which were used in parallel during the AROMAPEX campaign
Two additional compact imagers were operated from the Cessna: the SWING instrument and the Tropolite. These instruments are respectively designed to be operated from a UAV and a 12-Unit CubeSat. The FUBISS sun photometer and a compact KNMI NO2 sonde completed the experimental set-up in the Cessna.
In parallel with the airborne operations, car-based DOAS systems (MPIC, BIRA, UGAL) covered Berlin from North to South and West to East (Fig. 2). A set of static instruments (including two MAX-DOAS and a ceilometer) were installed and operated continuously at FUB for the period of the campaign. The campaign dataset also includes the measurements from the Berlin governmental in-situ network for air quality monitoring.
Fig 2. Two car-based DOAS systems operated in synergy with the aircraft (resp. MPIC-left and BIRA-right)
During this campaign, a major challenging factor was the spring weather, in particular the cloud cover. Indeed, operating airborne imaging instruments above an extended area such as Berlin requires stringent atmospheric conditions. Starting from the 11th of April (instruments integration on board of Cessna) until the 21th (the ''golden day"), the evolution of clouds development was continuously forecasted and the research flights were decided accordingly on a daily basis.
On April 21, the sky was finally clear and permitted two sets of flights (morning and afternoon) with both aircraft platforms (Cessna ≈3km altitude and Dornier ≈6km altitude), which were synchronised with the ground-based platforms. The preliminary results are promising and show a good concordance between the AirMAP, SWING, and mobile-DOAS retrievals of NO2 columns, which shows the same NO2 pattern of a large plume crossing the city in WE direction (Fig. 3), following the wind direction.
Fig 3. Preliminary mobile-DOAS and AirMAP measurement results of the morning flight, 21 April 2016
The AROMAPEX dataset is now being evaluated and will provide useful information, both on the air quality in Berlin and about the performances of the different instruments. The findings will be valuable in particular for space-based validation studies but they also may be of interest to constrain local air quality models.
The AROMAPEX project is supported both by EUFAR through its transnational access scheme which provided 10 fully-funded flight hours on board the Do-228 with the APEX instrument on-board, and by ESA in the framework of the Copernicus programme and the preparation of the Sentinel missions.