assessing the need for a o4 scaling factor for max -doas...

Mathematical formulation of the problem

Selection of well suited days during MADCAT

Available supporting data sets

Results, interpretation & outlook

Assessing the need for a O4 scaling factor for MAX-DOAS measurements during the MAD-CAT

campaign in Maing Germany, Summer 2013

T. Wagner, J. Remmers, R.Shaiganfar, J. Lampel, Y. Wang, S. Beirle, S. Dörner

Max-Planck-Institute for Chemistry, Mainz, Germany

measuredAMFVCDSCD

VCD

measured optical depth (of the O4 aborption at 360 nm) O4 aborption cross section SCD slant column density of O4 VCD vertical column density of O4 AMF Air mass factor

Are measurements and simulations in agreement for well defined situations, or is a scaling factor needed?

simulatedmeasured AMFAMF?

Are measurements and simulations in agreement for well defined situations, or is a scaling factor needed?

measuredAMFVCDSCD

VCD

measured optical depth (of the O4 aborption at 360 nm) O4 aborption cross section SCD slant column density of O4 VCD vertical column density of O4 AMF Air mass factor

simulatedmeasured AMFAMF?

Spectral analysis

T & p profiles

Different data sets, temperature dependence

Radiative transfer simulations

Two selected days

Clear days during MADCAT

Available data sets

Spectroscopy

MAX-DOAS measurements (4 azimuth directions)

Different O4 cross sections, including temperature dependence

AMF calculations & O4 VCD calculations

Ceilometer backscatter profiles (above 150m)

AOD from AERONET sun photometer

Surface measurements of pm2.5 and pm10

Temperature and pressure profiles from ECMWF

Surface measurements of temperature, pressure, rel. humidity

Standard O4 analysis at 360 nm

-wavelength range: 352 – 387 nm (two O4 bands)-Fraunhofer reference spectrum (FRS): 08.07., 10:05:35, SZA: 32.37°, elevation angle: 90°-calibration: using NDSC high resolution solar spectrum -cross sections:-O3, Bogumil et al., 223K-NO2 Vandaele, 298K-BrO, Fleischmann, 223K-O4, Thalmann, 293K-Ring 1-Ring 2 (Ring 1 -4)-polynomial of 5th order-intensity offset (second order polynomial)-measured spectrum is allowed to shift (versus FRS and cross sections)

Standard O4 analysis at 360 nm

Fit result for north-east direction, 08.07.2013, 11:21:54, elevation angle: 6°, SZA: 27.6°

Results for different spectral ranges

Fit result for north-east direction, 08.07.2013, 11:21:54, elevation angle: 6°, SZA: 27.6°

352-387nm:

O4 bands at 360nm and 380 nm

345-377nm:

O4 band at 360nm

335-377nm:

O4 bands at 340nm and 360nm

Influence of the wavelength range:Two other wavelength ranges are tested:-345-377nm: only the O4 band at 360nm-335-377nm: two O4 bands at 340nm and 360nm

Influence of the wavelength range:Two other wavelength ranges are tested:-345-377nm: only the O4 band at 360nm-335-377nm: two O4 bands at 340nm and 360nm

Influence of the wavelength range:Two other wavelength ranges are tested:-345-377nm: only the O4 band at 360nm-335-377nm: two O4 bands at 340nm and 360nm

0.8

0.9

1

1.1

1.2

3:36 6:00 8:24 10:48 13:12 15:36 18:00Time (08.07.2013)

Rat

io fo

O4

DS

CD

s (s

eque

ntia

l ref

.)

ratio_335_377nmratio_345_377nmRatio (340 & 360) / (360 & 380)Ratio (360) / (360 & 380)

1.00

0.97

The ratios are close to unity. The deviations of the results for 335 – 377nm can be explained by the wavelength dependence of the AMF.

Influence of the O4 cross section:-Greenblatt et al. (only interpolated)-Hermans et al.

The ratios of the O4 dSCDs are close to unity (especially if the Greenblatt et al cross section is allowed to shift)

0.8

0.9

1

1.1

1.2

2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12Time (08.07.2013)

Rat

io b

etw

een

O4D

SC

Ds

(fixe

d re

fere

nce)

ratio_burk_Thalratio_burkshift_Thalratio_Her_Thal

1.07

1.02

0.97

Only 293K

Only 203K

Both temperatures

Both temperatures, 293K orthogonalised

Both temperatures, 203K orthogonalised

Effect of the temperature dependence

Fit results for different combinations of O4 cross sections (original or orthogonalised)

7.68e-4

8.06e-4

7.65e-4

7.65e-4

7.65e-4

Effect of the temperature dependenceLarge difference are found for the retrieved O4 dSCDs:

colder effective temperatures in the morning

If low temperature cross section is used, the O4 dSCDs are underestimated by 30%

Effect of the temperature dependenceLarge differences are found for the retrieved O4 dSCDs (also forsequential FRS):

colder effective temperature in the morning

If low temperature cross section is used, the O4 dSCDs are underestimated by 30%

ECMWF

Surface measurements

O4 profile

temperature profile

18.06.2013

Profiles of pressuretemperaturehumidity

Calculation of the O4 VCDs for May to August 2013(based only on the surface pressure and temperature)

1.15

1.2

1.25

1.3

1.35

21.4 11.5 31.5 20.6 10.7 30.7 19.8 8.9

Time

O4

VC

D [1

043

mol

ec5/

cm²]

16.08. 08.07.

integration is performed between 150m and 30 km with a vertical resolution of 20m

RTM calculations are performed with MCARTIM (1)

-same t & p, and O4 profiles as used for determination of O4 VCD-vertical discretisation (150m =0m in RTM grid):-0m – 500m: 20m-500m – 2000m: 100m-2km – 12km: 200m-12km – 25km: 1km-25km – 45km: 2km-45km – 100km: 5km-100km – 1000km: 900km

-surface albedo: 5%, aerosol optical properties are varied-aerosol extinction profiles are derived from Ceilometer and AERONET AOD

Determination of aerosol extinction profiles1 8 .0 6 . , 0 8 :0 0 to 1 1 :0 0

- 1 .0 0 E + 0 9

0 .0 0 E + 0 0

1 .0 0 E + 0 9

2 .0 0 E + 0 9

3 .0 0 E + 0 9

0 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0A lt i t u d e [m ]

atte

nuat

ed b

acks

catte

r sig

nal

8 : 3 09 : 3 01 0 : 3 08 _ 1 1 h

1 8 .0 6 . , 0 8 :0 0 to 1 1 :0 0

0

0 .1

0 .2

0 .3

0 .4

0 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0a lt itu d e [m ]

Extin

ctio

n [1

/km

]

s lo p e _ 1 8 0 _ 2 4 0 md o u b le s lo p e _ 1 8 0 _ 2 4 0 mc o n s t

Extrapolation, smoothing, scaling to AERONET AOD

0

0 .1

0 .2

0 .3

0 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0a lt itu d e [m ]

Extin

ctio

n [1

/km

]

s lo p e _ 1 8 0 _ 2 4 0 ms lo p e _ 1 8 0 _ 2 4 0 mo r ig in a lw ith e x tin c tio n c o rre c tio n

0 8 .0 7 ., 0 4 :0 0 to 0 7 :0 0

Raw profiles from Ceilometer (1 hour averages)18.06., 8:00 – 11:00

Correction of aerosol self-extinction‘

Determination of aerosol extinction profiles

18.06., 08:00 to 11:00 18.06., 11:00 – 14:00 18.06., 14:00 – 19:00

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

08.07., 04:00 to 07:00 08.07., 07:00 – 11:00 08.07., 11:00 – 19:00

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

0

0.1

0.2

0.3

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240mslope_180_240moriginalwith extinction correction

Comparison of profiles without (blue) and with (magenta) extinction correction. Both profile versions are scaled to the same total AOD determined from the sun photometer.

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (08.07.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3

07:00 - 11:0004:00 - 07:0011:00 - 19:00

RTM results (AMF for 1° elevation, north-east direction)

Influence of time of day (T, p, O4, aerosol profiles)

08.07.2013

RTM results (AMF for 1° elevation, north-east direction)

Influence of extrapolation of aerosol profile below 180m

08.07.2013

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (08.07.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3

linearly extrapolated below 180mconstant below 180mlinearly extrap., double slope below 180m

RTM results (AMF for 1° elevation, north-east direction)

Influence of aerosol optical properties

08.07.2013

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (08.07.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3elev_3

HG, asymmetry parameter 0.68HG, asymmetry parameter 0.60HG, asymmetry parameter 0.75HG, asymmetry parameter 0.85

RTM results (AMF for 1° elevation, north-east direction)

Influence of aerosol optical properties

08.07.2013

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (08.07.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3

Single scattering albedo 0.95Single scattering albedo 0.90Single scattering albedo 1.00

RTM results (AMF for 1° elevation, north-east direction)

Influence of surface albedo

08.07.2013

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (08.07.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3

Surface albedo: 0.05Surface albedo: 0.03Surface albedo: 0.10

Comparison result for one azimuth direction

The RTM results systematically underestimate the measured AMF. Similar results for all azimuth directions and low elevation angles

08.07.2013, 3° elevation towards north-east

0

1

2

3

4

5

6

7

3:00 7:00 11:00 15:00 19:00Time (08.07.2013)

O4

DA

MF

measurementssimulations 4h – 7hsimulations 7h – 11hsimulations 11h – 19h

measurementssimulations 4h – 7hsimulations 7h – 11hsimulations 11h – 19h

O4 AMF

O4 DAMF

0

1

2

3

4

5

6

7

3:00 7:00 11:00 15:00 19:00Time (18.06.2013)

O4

DAM

F

s

On the morning of 18.06 RTM results are higher than measured O4 dSCDs

What is the reason?

O4 AMF

O4 DAMF

Aerosol concentration measured by in situ instruments

In the morning of 18.06. high aerosol load was found close to the surface

0

10

20

30

40

50

3:00 7:00 11:00 15:00 19:00Time

pm2.

5 [µ

g/m

³]

blue: 18.06.red: 08.07.

ZitadelleParcusstrasseWI Ringkirche

0

10

20

30

40

50

60

70

3:00 7:00 11:00 15:00 19:00Time

pm 1

0 [µ

g/m

³]

blue: 18.06.red: 08.07.

ParcusstrasseZitadelleMombachWI Schierst.WI Sued

Modified aerosol extinction profile for morning of 18.06. 2013

The values below 180m are set to three times the values of the profile with linear extrapolation below 180m. The total AOD is changed from 0.38 (average value) to 0.41 (close to maximum during that period).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 1000 2000 3000 4000 5000 6000altitude [m]

Ext

inct

ion

[1/k

m]

slope_180_240m

double slope_180_240m

const

three times extinction_AOD041

RTM results (AMF for 1° elevation, north-east direction)

Results for the modified profile are much smaller

18.06.2013

0

1

2

3

4

5

6

03:00 07:00 11:00 15:00 19:00Time (18.06.2015)

O4

AM

F (1

°)

elev_3elev_3elev_3Reihe4

linearly extrapolated below 180mconstant below 180mlinearly extrap., double slope below 180m3 times extinction below 180m, AOD 0.41

0

1

2

3

4

5

6

7

3:00 7:00 11:00 15:00 19:00Time (18.06.2013)

O4

DAM

F

s

measurementssimulations 8h – 11hsimulations 11h – 14hsimulations 14h – 19h

Profile inversions using parameterised methodComparison to Ceilometer

0

1000

2000

3000

4000

3:00 7:00 11:00 15:00 19:00Time

heig

ht [m

]

18.06. shape factor: 0.8sclaing factor: 0.8

0

1000

2000

3000

4000

3:00 7:00 11:00 15:00 19:00T ime

heig

ht [m

]08.07.

shape factor: 0.8scaling factor: 0.8

0

0.2

0.4

0.6

0.8

3:00 7:00 11:00 15:00 19:00Time

AO

D (3

60 n

m)

Reihe1Reihe2Reihe3Reihe4

fact: 0.7fact: 0.8fact: 0.9AERONET

18.06. shape factor: 0.8

0

0.2

0.4

0.6

0.8

3:00 7:00 11:00 15:00 19:00Time

AO

D (3

60 n

m)

Reihe1Reihe2Reihe3Reihe4

fact: 0.7fact: 0.8fact: 0.9AERONET

08.07. shape factor: 0.8

Profile inversions using parameterised methodComparison to Ceilometer

0

1000

2000

3000

4000

3:00 7:00 11:00 15:00 19:00Time

heig

ht [m

]

18.06. shape factor: 0.8sclaing factor: 0.8

0

1000

2000

3000

4000

3:00 7:00 11:00 15:00 19:00T ime

heig

ht [m

]08.07.

shape factor: 0.8scaling factor: 0.8

Comparison of aerosol extinction / pm2.5 & pm10 on both days

0

10

20

30

40

50

3:00 7:00 11:00 15:00 19:00Time

pm2.

5 [µ

g/m

³]

blue: 18.06.red: 08.07.

ZitadelleParcusstrasseWI Ringkirche

0

10

20

30

40

50

60

70

3:00 7:00 11:00 15:00 19:00Time

pm 1

0 [µ

g/m

³]

blue: 18.06.red: 08.07.

ParcusstrasseZitadelleMombachWI Schierst.WI Sued

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

3:00 7:00 11:00 15:00 19:00time

Ext

inct

ion

[1/k

m]

Reihe10Reihe118.06.201308.07.2013 MAX-DOAS aerosol extinction

(AOD / layer height)

Surface in situ measurements

Summary

-measured O4 AMFs (and dAMFs) on 08.07.2013 are by about 20% larger than simulated ones (on 18.06. differences are smaller)-RTM uncertainties or choice of cross sections and fit settings can not explain these differences

-for the selected days the calculation of the O4 VCD is very accurate (but changes of the O4 VCD are > 10% during the MADCAT period due to pressure and temperature variations)-temperature dependence of O4 cross section is large (30% change of O4 dSCD for 100K temperature difference), but can not explain the observed differences on the selected days.

-the need for scaling factor remains unexplained

-all steps should be repeated by other participants (using also measurements from other instruments)

I will send out email with detailed information soon.