Hester Volten, Ellen Brinksma, Stijn Berkhout, Daan Swart, René van der Hoff,

Hans Bergwerff, Pieternel Levelt, Gaia Pinardi, Michel Van Roozendael

NO2 lidar profiles measured during the DANDELIONS validation

campaign 2006

“How representative is an OMI measurement for surface concentrations?”

DANDELIONS Sept. 2006 – Objectives

O3 : total column and profile (sondes)

tropospheric contributionNO2: lower tropospheric profile

(lidar) total columns (focus: pollution) MAXDOAS intercomparisonAerosol: radiosondes, CIMEL, SPUV,

aethalometer

CESAR site (Cabauw, 51.971°N, 4.927°E) • many continuous measurements• full meteorological info at location

2007 research questions (for NO2): 1) Shape of NO2 profiles (and influence

on OMINO2) for industrial area2) Homogeneity of the NO2 field

Dutch Aerosol and Nitrogen Dioxide Experiments for vaLIdation of OMI and SCIAMACHY

Cabauw

industry

industry

Clean air

CESAR

industry

Participating Institutes and Instruments OMI, SCIAMACHY

RIVM NO2 lidar, NO2 in-situ monitors, boundary layer lidar

BIRA-IASB MAXDOAS, Mini MAXDOASIUP Heidelberg MAXDOAS (three directions)IUP Bremen MAXDOAS NASA-GSFC Direct Sun Instrument (Pandora)KNMI Mini MAXDOAS, ozone sondes, radio sondes TNO Sun photometers, volatility system, aethalometer, nephelometer, etc.

Nine validation days on Sept 8-13, 20-22Data publicly available on AVDC http://avdc.gsfc.nasa.gov

 

The third dimension: NO2 lidar – ground level to about 2.5 km

NO2 in-situ monitor - on the ground and at 200 m Mini MAXDOAS - on the mast (200m)

Mobile NO2 Lidar telescope

Rapid switching between two wavelengths

55

50

45

40

35

30

25

20

Tra

nsm

itta

nce (

%T

)

451450449448447446

Wavelength (nm)

448.31 nm (on)

449.10 nm (off)

How to Measure a Profile

300 m

NO2 Lidar Measurements during the DANDELIONS campaign

• NO2 profiles during overpasses – seven different elevations 0.75, 1.5, 3, 6, 12, 24, 90 deg, 1 azimuth (39 degrees)

• Spatial variations – two azimuths (39 and -36 deg), 1 elevation (12 degrees)

• Time variations – 1 azimuth (39 degrees) , 1 elevation (12 degrees), long time series

EXAMPLE: 12 SEPTEMBER in-situ monitor comparison Mini MAXDOAS heterogeneity

Overview of all NO2 lidar measurementsSeptember 2006

Profile assumed in OMI retrieval

concentration NO2 (g/m3)500 10 20 30 40

500

1000

1500

60

Alti

tude

(m

)Profile shape influences OMI retrieval

OMI L4 tropospheric columns12 September-polluted day

NO2 lidar profile compares well with in-situ data

2500

2000

1500

1000

500

0

alti

tud

e (

m)

6050403020100

concentration NO2 (µg/m3)

profile 09:37 - 10:26 UT in-situ 09:37 - 10:26 UT

SCIA overpass 9:59 UT

12 September 2006

boundary layer 10:00 UT

0,1,2,3,4,5,6,8,10, 12,14,16,20,25,30

-10,-8,-6,-4,-3,-2,-1

Example Mini MAXDOAS measurementHigh sensitivity to the vertical NO2 distribution in the lowest 200 m

Zenith

Julian day

Boundary layer growth

NO2 layer below 200 m

NO2 layer above 200 m

NO2 lidar profile compares badly with in-situ data

2500

2000

1500

1000

500

0

alti

tud

e (

m)

605550454035302520151050

concentration NO2 (µg/m3)

profile 12:42 - 13:06 UT in-situ 12:42 - 13:06 UT

12 September 2006

boundary layer 13:00 UT

OMI overpass 12:47 UT

Heterogeneity on 12 SeptemberNO2 lidar - different azimuth angles

400

350

300

250

200

150

100

50

0

alti

tud

e (

m)

50454035302520151050-5

concentration NO2 (µg/m3)

12 September 2006

10:31 - 10:51 UT

azimuth -36 deg azimuth +39 deg

elevation 12 deg

Heterogeneity on 12 September NO2 lidar - time series

10:50 10:55 11:00 11:05 11:10 11:15 11:20 11:25 11:30 11:35

time

50

45

40

35

30

25

20

15

10

con

cen

tra

tion

NO

2 (

µg

/m3)

low altitude 75 m -155 m high altitude 160 m - 270 m

averages over 3.75 minutes

12 September 200610:55 - 11:33 UT

elevation 12 deg

Lidar values smaller or the same as in-situ values

60

50

40

30

20

10

0

conc

entr

atio

n N

O2 (

µg/

m3)

9/6 9/7 9/8 9/9 9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23

date

in-situ 0 m in situ 200 m lidar 0 m lidar 200 m

No problem

Problem !

Lidar versus in-situNH3 interference in-situ monitors?

60

50

40

30

20

10

0

conc

entr

atio

n N

O2 (

µg/

m3 )

9/6 9/7 9/8 9/9 9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23

date

in-situ 0 m in situ 200 m lidar 0 m lidar 200 m NH3 Zegveld 0 m

No solution: Error through NH3 interference cannot be larger than 6%

Conclusions• We had a hugely successful DANDELIONS

campaign in 2006. Data is available on AVDC.

• NO2 lidar profile shapes differ quite a lot from OMI assumption

• Concentrations on clear and polluted days show large variations, from ~3 to ~50 g/m3

• Heterogeneity in space and time is sometimes very large

• In-situ data and lidar data do not always agree