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Ankie Piters
Royal Netherlands Meteorological InstituteMinistry of Infrastructure and Environment
Measuring vertical profiles and tropospheric columns of NO2
photo: A. Apituley
photo: T. Vlemmix
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Atmospheric Composition Research
Main Scientific Themes: ozone layer, air quality, and chemistry-climate interactionDivision: 76 people (of which ~40 on OMI/TROPOMI - PI)
Observation group:Satellite observations: retrieval, validation and distribution of data. OMI, TROPOMI/S5p, GOME, SCIAMACHY, GOME-2, SEVIRI.
Main products: O3, NO2, aerosols, cloudsGround-based measurements important for satellite and model validation
Modelling group:
Coupling TM5 to EC Earth , focus: aerosols and non-CO2 GHGAir quality forecastsData assimilation
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Ground-based measurements of O3 and NO2
operational measurementsozonesondes in De Bilt since 1992ozonesondes in Paramaribo (Surinam) since 1999
Brewer (O3 column) in De Bilt and Paramaribo (1994/1999)
2 MAX-DOAS (trop NO2) in De Bilt/Cabauw (2008)participation in global networks: GAW/WOUDC, SHADOZ,
NDACC
instrument development: NO2 sonde development since 2008
campaigns in Cabauw (focus NO2)DANDELIONS 2005 & 2006CINDI 2009PEGASOS, 2012
other campaigns (with NO2 sonde)DISCOVER-AQ, Washington/Baltimore, 2011ACTRIS, Hohenpeissenberg, 2012DISCOVER-AQ, California, Jan-Feb 2013VOGA-NCP, Beijing area, June 2013
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MAX-DOAS
side-by-side intercomparison:
4 sondes + 2 NOx analysers
NO2 sonde preparation
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Cabauw – increasing satellite validation potential (chemistry)
Cabauw:• Tropospheric air representative for
satellite pixel sizes• Wide range of pollution levels, no local
sources nearby (except for farms!)• Vertical information (tropospheric columns)
with remote sensing instruments, complemented with in-situ on site and in tower.
Gases of interest:• O3, NO2, CO2, AOD, CO, CH4, HCHO, H2O and SO2
Long-term goals• Organise campaigns for satellite validation• Maintain current operational NO2 measurements• Increase potential of Cabauw with an FTS instrument measuring vertical columns
and profiles of GHG (together with ECN)
picture: Ronald van der A, KNMI
global NO2 distribution based on OMI data
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FTIR visit in Cabauw
Mobile FTIR from BIRA
Columns and profiles of CH4, CO, and N2O between May and July 2013 (PEGASOS and INGOS)
CO
N2O
CH4
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MAX-DOAS
• spectrum of scattered sunlight at different elevation angles
• tropospheric NO2 from differential absorption w.r.t. zenith (strat. NO2)
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Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments
overview: Piters et al, AMT, 2012
Wittrock et al., in prep., AMT
Photo: M. Kroon
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MAX-DOAS tropospheric NO2 compared to OMI
Vlemmix et al, AMT, 2010
When aerosol correction applied: no sign. bias between OMI and MAX-DOAS
σGB< 30% : R=0.64 (grey)
σGB< 20% : R=0.73 (black)
σGB< 10% : R=0.88 (red)
Spread larger than expected from retrieval errors alone.
Difference in spatial representativity
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Use of MAX-DOAS data in model verification
Average trop NO2 for different wind directions(5.1015 molec cm-2 per circle)
National Air Quality Model Lotos-Euros
Sunday
Vlemmix et al., ACPD 2012
measurements from De Bilt
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The NO2 sonde
- Measures high resolution NO2 profiles
- Light weight- Low power consumption- Can be launched on small weather
balloon
Idea: Wesley Sluis
Design: Marc Allaart
Chemistry: Mirjam den Hoed
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The NO2 profiles
up to ~10km (balloon burst)
two profiles for each launch (‘up’ and ‘down’)
large variability in shapes
Winter 2010-2011
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sonde on tethered balloon:
- build up of boundary layer
- development of detailed structures
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Measurement principle
based on chemiluminescent reaction of NO2 with luminol
photons are detected with photodiode array
electronics: converts femto-amperes to millivolts
luminol reservoir prevents acidification by CO2
Sluis et al., AMT, 2010
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NO2 variations are very well captured.
RMS difference is <10%
absolute calibration still to be optimized (here: constant scaling factors applied)
How accurate can we measure NO2?
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Demonstration for OMI NO2 validation
Red: a priori (model) profile used for satellite retrievals
Black: NO2 sonde profile
Difference in profile shape results in errors up to 50% in satellite NO2
21 May 2012
error: ~5%
22 May 2012
error: ~50%
Piters et al., ACVE, 2013
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Comparing with AQ models
Thanks to: Henk Eskes and Patricia Castellanos, KNMI
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Modeled NO2 above boundary layer
24h backtrajectory at 1km height= measured air mass
The Lotos-Euros model shows:
NO2 vertical transport to the free troposphere
Horizontal transport of free tropospheric NO2
Possible origin of difference with sonde:
Life time of NO2
Vertical/horizontal transportSurface emissions
1km, start of back-trajectory
BL (model)
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Weather balloon
NOx analysersRIVM/LML
Photo: A. Apituley
PEGASOS campaign May 2012, Cabauw
(only NO2 instruments are shown)
zeppelin
Marc and Ankie with NO2 sondes
NOx analyser @200mRIVM
NO2 lidarRIVM
mobile lab (Juelich)
MAX-DOAS (2x)
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500 m
6:00 7:00 8:30 9:45
EURAD model (Univ. Cologne) 1200 m
0 m
27-5-2012
NO2 concentration (arbitrary offset and scaling)
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Future plans ...
• Optimisation of the calibration• Optimisation of the design• Transfer knowledge to industry for
serial production• Use it for the validation of models,
MAXDOAS and indirectly of satellites
Marc and Deborah recovering a sonde
Photo: A. Apituley