Infrared quantitative

spectroscopy and

atmospheric satellite

measurements

Jean-Marie Flaud

Laboratoire Interuniversitaire des Systèmes

Atmosphériques

CNRS, Universités Paris Est Créteil et Paris Diderot

THE MIPAS EXPERIMENT

• Phosgene (COCl2), • H14NO3 , • Questions/Comments

OUTLINE

MIPAS

• The MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) instrument is a Fourier transform spectrometer that measures earthlimb emissions in the 685-2410 cm−1 range with an unapodized resolution of 0.035 cm−1, and with high sensitivity,

• The spectral resolution of the instrument permits to obtain the atmospheric spectra with an unprecedented accuracy.

• Day and night

(J.-M. Flaud and H. Oelhaf, Infrared spectroscopy and the terrestrial atmosphere, C. R.

Physique 5 (2004) 259–271)

A MIPAS SPECTRUM

Phosgene (COCl2) in the UTLS:

vertical distribution from MIPAS

observations using new

spectroscopic data at 11.65µm

Phosgene in the UTLS region

• It is absorbing in the same spectral region as CFC11!

• Phosgene (COCl2) in the 20th century was mainly used by

chemical industry in the preparation of insecticides,

pharmaceuticals and herbicides.

Why to study phosgene?

Previous studies • First study about atmospheric phosgene: Singh (1976) studied the surface

distribution of phosgene using data from six stations in California.

• Wilson et al. (1988) measured phosgene at various altitudes during an aircraft

flight over Germany.

• Toon et al. (2001) used the Jet Propulsion Laboratory - MkIV Interferometer,

onboard stratospheric balloons, to retrieve different VMR profiles of phosgene

from 1992 to 2000.

• First satellite measurements of stratospheric phosgene: Fu et al. (2007) used

ACE-FTS measurements to make the first analysis of the global distribution of

phosgene.

• Using data acquired by the same experiment, Brown et al. (2011) focused their

work on the study of phosgene inter-annual variations.

But these studies were not using high resolution spectra

Cross sections from PNNL are not sufficient

because not covering the atmoshere

temperatue range

High resolution spectra of the ν5 bands of

CO 35Cl 37Cl, CO 35Cl 37Cl and CO 37Cl 37Cl

were recorded and analysed

Estimation of the abundances of the

various isotopic species of phosgene

Abundance Abundance

35Cl 0.7578 CO 35Cl 35Cl 0.5743

37Cl 0.2422 CO 35Cl 37Cl 0.3671

CO37Cl 37Cl 0.0587

High resolution analysis of the ν1 and ν5 bands

of phosgene 35Cl2CO and 35Cl37ClCO

FTS spectra of phosgene have been recorded in the 11.75 μm and 5.47 μm spectral regions at a resolution of ~0.00125 cm-1 leading to the observation of the ν5 and ν1 bands of the three isotopologues 35Cl2CO, 35Cl37ClCO and 37Cl2CO. The upper state ro-vibrational levels were fit to within the experimental accuracy i.e. ~0.17 x10-3 cm-1. using Hamiltonians accounting for resonance effects when necessary and in this way it proved possible to simulate the observed spectra to within experimental accuracy.

Hot bands

Phosgene low resolution spectrum

[PNNL] around 11.65µm

Bands calculated to model the absorption cross

sections of Phosgene at 11.65µm

ISOTOPIC

SPECIES

VIBRATION

AL BAND

INTENSITY

(cm-1 /

molecule.cm-2)

Number of

lines

3535Cl2

GROUND--

>V5 0.216D-16

46052

3535Cl2 V3-->V3+V5 0.105D-16 42104

3535Cl2 V6-->V5+V6 0.602D-17 38440

3535Cl2 V2-->V2+V5 0.162D-17 29500

3537Cl2

GROUND--

>V5 0.139D-16

43784

3537Cl2 V3-->V3+V5 0.625D-17 38699

3537Cl2 V6-->V5+V6 0.313D-17 33872

3737Cl2

GROUND--

>V5 0.387D-17

35361

(The intensities account for the isotopic abundances)

Observed (red) and calculated (green) X- sections at 5 C

Missing hot band

Summary and conclusions

We studied the phosgene global distribution using:

• the new phosgene spectroscopic database ,

• the new MTR functionality of the ORM (COCl2 and CFC-11 joint retrieval),

• more than 28000 profiles retrieved from MIPAS in the 2008 year.

MIPAS allowed to highlight the seasonal and latitudinal variations:

• largest values in the tropical regions,

• less peaked vertical distributions in the mid-latitude and polar regions,

• no seasonal variability in the UTLS apart for a weak seasonality in the polar regions,

• the lowest average values occur in the South Polar Winter (JJA).

Results – Polar bands

The average profiles do not exceed 30 pptv with maxima at around 100 hPa. Only in the polar regions we observe a weak seasonality.

MIPAS database

Goal: Retrieve HNO3 using

simultaneously the 11 and 7.6 µm regions

New H14NO3 line parameters at 7.6 µm

derived from MIPAS satellite measurements and

laboratory intensity measurements

MW & n9 {n5,2n9) {n4,n3} n2

0-10cm-1 458cm-1 879, 896cm-1 1303, 1326cm-1 1709cm-

Far-IR 22µm 11µm 7.6µm

MIPAS

Enables a simultaneous measurement of

HNO3 both at 11 µm & 7.6 µm using MIPAS

spectra

¤ As a starting point, we use the 2013 list of

line positions and relative line intensities at

7.6 µm

Process

¤The 11 µm band line parameters were kept as

they are in HITRAN or GEISA

¤The new 7.6 µm parameters (line positions

and relative intensities) were improved

relatively to those at 11 µm.

Strategy for improving the

7.6 µm region (H14NO3)

We used and combined three sets of experimental data

¤ A list of laboratory experimental (individual) line

positions and intensities measured in the 7.6 µm region

using FTS spectra recorded in 2004 at Giessen.

¤ MIPAS spectra (orbit 04712 from 24 january 2003)

¤ The Pacific Northwest Laboratory (PNNL) cross sections

Hamiltonian matrix

Old database at 7.6 µm

New database at 7.6 µm

About 350 line intensities were measured using an FTS

spectrum recorded in the 7.6 µm region (P?)

Ratio R=MIPAS-new/ Measured line intensities

The Pacific Northwest Laboratory cross sections

(https://secure2.pnl.gov/nsd/nsd.nsf/Welcome)

HITRAN-2012

HITRAN-2012

Conclusion

Atmospheric spectra can be used

to improve spectroscopic

databases

What are the problems?

3 Many species( O3, HCHO, H2O,C2H6, …) are measured in various spectral regions with different instruments

•How to perform really meaningful comparisons of concentration

profiles obtained by spectrometric measurements in various spectral

regions

•How to perform simultaneous retrievals in different spectral regions

if the corresponding the line parameters are not consistent

1 The possibility of the retrievals is directly linked to the availablity of the spectroscopic parameters

2 The quality of the retrievals is directly linked to the quality of the spectroscopic parameters

SEED QUESTIONS

• What are the spectroscopic needs?

• Where are recognised weaknesses?

• Which new species are relevant and why ?

Together with other groups!

• What about line shapes, continuum absorption

• How is the consistency between different

wavelength ranges (e.g. UV, SWIR, TIR)?

• Auxiliary data: what/how/why? (e.g. micro-

windows, climatology)

Spectroscopy for infrared limb/nadir sounders

Some comments:

• Only a small amount of the MIPAS data is used in the level 2 analysis

• Is redundant and new information properly used?

• Independent set of (micro)windows in level 2 can be used to assess

data product uncertainty including spectroscopy

Status of IR spectroscopic databases

• Still missing quantified uncertainties ( Especially for air broadening

and temperature dependences, and air pressure shifts and

temperature dependences).

• Line narrowing almost entirely missing

• In case of absorption cross sections: often insufficient spectral

resolution, missing air pressure and temperature dependences, errors

due to temperature inhomogeneity

• Some molecules like CO2, H2O, CO, HCl, HF, N2O and O3 seems to be

in “reasonable” shape

Spectroscopy for infrared limb/nadir sounders

Error propagation into level 2

• Global scalar error for trace gas profiles (contributing errors are scalar

line intensity errors): this error is not fully critical since, in principle, it

can be removed by validation. However accuracies of 1-10% are

extremely difficult to reach

Need to use laboratory and/or atmospheric spectra

• Spectroscopic errors with contributions varying with pressure and

temperature and thus height, geolocation, time of year, day – night are

extremely difficult to estimate.

Question: Can rigorous retrieval simulations for the MIPAS data products

regarding these issues give an answer? How can the microwindow

selection tackle these issues?

Spectroscopy for infrared limb/nadir sounders

Some “ideas” to improve the spectroscopic databases:

• Identify species where specific scientific issues require an improved

data quality and consistency

• Test the impact of spectroscopic error by doing retrievals with

different microwindow sets, however this does not unambiguously

point out to spectroscopic errors

• Perform the “right spectroscopic” studies

• ………………………………

I WOULD LIKE TO THANK:

H14NO3

A. Perrin, M. Ridolfi, J. Vander-Auwera, M. Carlotti

THANK YOU FOR YOU ATTENTION

Phosgene

M. Valeri , M. Carlotti, P. Raspollini, M. Ridolfi, B. M. Dinelli