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Additional observations,comparison of datasets and validation


During the observation flights, additional observations were made to provide correlative comparisons and to validate APEX data. These additional observations were performed using ground based Differential Optical Absorption Spectroscopy (DOAS) instruments from BIRA. Two types of measurements were conducted:

(1) MAXDOAS measurements at a fixed location allowing for the determination of the NO2 vertical distribution every 20 minutes

(2) mobile DOAS measurements from a car providing NO2 vertical columns at a resolution of approximately 50 m, compatible with APEX measurements.

In addition, all available in situ observations from the measurement surface network of the Environment Agencies were gathered and aerosol information from operational CIMEL sunphotometers were used. During the APEX acquisition flights VITO-TAP performed additional in situ measurements for calibration/validation of the acquired data sets. For in situ, spectrometer data will be gathered as well as sunphotometer measurements by means of both Microtops and CIMEL sunphotometers.


This work package resulted in following deliverables:
- Additional observations performed during the WP2 campaigns based on ground-based MAX-DOAS and Mobile-DOAS
- Correlative comparison statistics and validation of the retrieved APEX NO2 columns.
- Full NO2 VCD error budget