Ankie Piters

Royal Netherlands Meteorological InstituteMinistry of Infrastructure and Environment

Measuring vertical profiles and tropospheric columns of NO2

photo: A. Apituley

photo: T. Vlemmix

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

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

MAX-DOAS

side-by-side intercomparison:

4 sondes + 2 NOx analysers

NO2 sonde preparation

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

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

MAX-DOAS

• spectrum of scattered sunlight at different elevation angles

• tropospheric NO2 from differential absorption w.r.t. zenith (strat. NO2)

Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments

overview: Piters et al, AMT, 2012

Wittrock et al., in prep., AMT

Photo: M. Kroon

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

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

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

The NO2 profiles

up to ~10km (balloon burst)

two profiles for each launch (‘up’ and ‘down’)

large variability in shapes

Winter 2010-2011

sonde on tethered balloon:

- build up of boundary layer

- development of detailed structures

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

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?

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

Comparing with AQ models

Thanks to: Henk Eskes and Patricia Castellanos, KNMI

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)

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)

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)

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