plans to study horizontal no 2 distribution ankie piters, tim vlemmix, knmi data from: inta, iupb,...
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Plans to study horizontal NO2 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
IUPB, INTA, JAMSTEC (287o) 10-25 July
NASA_P2 (66o) 14-20 July
Leicester (326o) 10-22 July
NASA_P3 (187o) 14-20 July
KNMI (253o) 14-25 July
more directions anticipated from: BIRA, IUPB, IUPH
Idea
• use different times and viewing directions
• transport each measurement with the current wind to satellite overpass time
• determine horizontal distribution of NO2 inside satellite pixel
What is the effective location of the measurement?
• Somewhere between top op PBL and surface?
? ? ?
20 July, between 6 and 10:
• average wind speed at 200m: 8.7 m/s
• average wind direction at 200m: 264o
• line IUPB – NASA_P2: 266.5o
similar air mass observed by IUPB
and NASA_P2, with time delay
DSCD*AMFgeom
• time delay is clearly visible
• calculate correlation as a
function of time delay
elevation 30o
elevation 15o
R
time delay (hour)
-0.11-0.20
time delay distance
• 0.11 hour at 8.7 m/s 3.4 km for 30o elevation
• 0.2 hour at 8.7 m/s 6.3 km for 15o elevation
• variations in NO2 signal originate at 1.8 km for 30o
elevation and 3.4 km for 15o elevation (for this day)
3.4 km (6.3 km)
1.8 km (3.4 km)139o
20.5o
distance altitude
• the variations in NO2 we see
on 20 July, 6-10h, are
originating at ~0.9-1 km
• BLH, cloud base?
• other examples?
3.4 km 1.8 km
1 km
0.9 km30o
15o
How can the data be combined?
• All data processed with same settings (semi-blind
intercomparison)
• Correct for known differences between instruments
• Subtract dscd at 90o, closest in time
• Use measured AOT, BLH
• Use correct AMFs
• measurements
transported to OMI
overpass time
Cabauw
latitude
latitude
long
itude
long
itude
OMI pixel
OMI pixel
30o elevation
4o elevation
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
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, 30/15o 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.
to do ….
• collect data:
– NO2 DSCD data for the period 10-25 July: BIRA, IUPB, IUPH
– reference data: NO2 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
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