1. Plans to study horizontal NO 2 distribution Ankie Piters, Tim Vlemmix, KNMI data from: INTA, IUPB, JAMSTEC, KNMI, Leicester, NASA Objectives: –Satellite pixel inhomogeneity –3D-field of view of MAXDOAS-like instruments

2. IUPB, INTA, JAMSTEC (287 o ) 10-25 July NASA_P2 (66 o ) 14-20 July Leicester (326 o ) 10-22 July NASA_P3 (187 o ) 14-20 July KNMI (253 o ) 14-25 July more directions anticipated from: BIRA, IUPB, IUPH

3. Idea use different times and viewing directions transport each measurement with the current wind to satellite overpass time determine horizontal distribution of NO 2 inside satellite pixel

4. What is the effective location of the measurement? Somewhere between top op PBL and surface? ? ? ?

5. 20 July, between 6 and 10: average wind speed at 200m: 8.7 m/s average wind direction at 200m: 264 o line IUPB – NASA_P2: 266.5 o  similar air mass observed by IUPB and NASA_P2, with time delay

6. DSCD*AMF geom time delay is clearly visible calculate correlation as a function of time delay elevation 30 o elevation 15 o

7. R time delay (hour) -0.11-0.20

8. time delay  distance 0.11 hour at 8.7 m/s  3.4 km for 30 o elevation 0.2 hour at 8.7 m/s  6.3 km for 15 o elevation variations in NO 2 signal originate at 1.8 km for 30 o elevation and 3.4 km for 15 o elevation (for this day) 3.4 km (6.3 km) 1.8 km (3.4 km) 139 o 20.5 o

9. distance  altitude the variations in NO 2 we see on 20 July, 6-10h, are originating at ~0.9-1 km BLH, cloud base? other examples? 3.4 km1.8 km 1 km 0.9 km 30 o 15 o

10. How can the data be combined? All data processed with same settings (semi-blind intercomparison) Correct for known differences between instruments Subtract dscd at 90 o, closest in time Use measured AOT, BLH Use correct AMFs

11. measurements transported to OMI overpass time Cabauw latitude longitude OMI pixel 30 o elevation 4 o elevation

12. dAMF, 8 UT AOT=0.2, BLH=1.0 km AOT=0.3, BLH=1.0 km AOT=0.2, BLH=0.9 km NASA_P2 IUPB

13. summary Effective measurement location for 20 July is near the boundary layer height, how about other days/situations? The lower elevation angles can be used to ‘fill up’ an OMI pixel, 30/15 o will give only one dimension Trying to get overlapping data consistent will give more insight in the validity of the AMFs and the assumptions used in the calculation of the AMFs.

14. to do …. collect data: –NO 2 DSCD data for the period 10-25 July: BIRA, IUPB, IUPH –reference data: NO 2 lidar (RIVM), in-situ data (Bremen, RIVM, EMPA), direct sun (BIRA, NASA) and zenith sky (CNRS) –auxiliary data: aerosol, BLH, clouds study (in-)consistencies for same air mass observations determine horizontal gradients for selected days, possibly combined with the mobile measurements (BIRA, CNRS, MPI) compare to satellite data make recommendations on observation strategies