Laboratory spectroscopy at DLR

Manfred Birk, Georg Wagner, Joep LoosGerman Aerospace Center (DLR)

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014DLR.de • Chart 1

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

• Group established in 1990• Emphasis on quantitative spectroscopy of atmospheric trace gases• Support of atmospheric remote sensing• Initial focus on far infrared• Soon extended to mid and near infrared; extended to UV in 2010• Participation in several EU-, ESA- and nationally-funded projects• Member of HITRAN scientific advisory committee

Background

DLR.de • Chart 2

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

• Bruker IFS 120HR Fourier-transform spectrometer• Replaced by new Bruker IFS 125HR in August 2010, extension to UV (250 nm)• Coolable (190 K), heatable (950 K) cells, 170 m multireflection cell• Lab equipment for production/handling of stable/unstable species

Infrastructure

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• 20 cm absorption path• Path length accuracy 0.1 % - requires raytracing!• Coolable to 190 K• High temperature homogeneity (0.1 K)• Two window pairs allowing UV+MIR, MIR+FIR, UV+FIR

New short absorption path cell

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014DLR.de • Chart 4

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

• Designed at DLR in 1991, refurbished in 2012• 80 cm baselength, up to 170 m absorption path• Coolable to 190 K• Equipped for flow experiments with unstable species

Multireflection cell

DLR.de • Chart 5

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

• Adaptable detector FOV to reduce background photon noise• Coolable optical filter• Photoconductive MCT with 700 cm-1 cut-on @ 45 K

Improved detector design for thermal IR

DLR.de • Chart 6

Intercomparison standard Bruker MCT – DLR design• Optical band pass filter, varying central wavenumber• Detector @ 45 K• 200 cm filter bandwidth• 1 mm and 2 mm Bruker entrance aperture• No absorber- and 90% absorption-setup

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

New IDL multispectrum fitting tool

DLR.de • Chart 7

• Line models• Voigt• Speed-dependent Voigt (C. Boone)• Speed-dependent Galatry + LM (F. Hase)• pCqSDHC + LM (Ngo, Tran)

• Versatile interactive mode• Choice of line model, fitparameters• ILS, calibration factors, baseline, channelling, …

• Automatic mode• Microwindow-, spectra-, fitparameter selection (Voigt)• Goodness-of-fit• Residua analysis (planned)

• Identification/prevention of correlation between fitted parameters

• Filecuts (results of single-spectra-fits vs. ms-fit)• Identification of systematic spectrum-specific errors

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

New IDL multispectrum fitting tool

DLR.de • Chart 8

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014DLR.de • Chart 9

Spectroscopic database work at DLRspecies FIR MIR NIR purpose/application remark

O3 S, g(T) s, S, g(T), a(T, p) database improvement

ClONO2 a(T, p) database improvement, MIPAS difficult synthesis

N2O5 a(T, p) database improvement, MIPAS

OH/HO2 s new lethodology extremely unstable

BrO s, g(T) database improvement, MASTER/SOPRANO extremely unstable

ClO s, g(T) s, S database improvement, MASTER/SOPRANO unstable

ClOOCl s a(T, p) remote sensing, MIPAS sample preparation difficult

HOCl s FIR database

CO S, g(T) S, g(T) error characterisation, high temperature database, Q/A <1% radiometric accuracy

CO2 a(T, p) high temperature database

H2O s, S, g(T) s, S, g(T), g2high temperature database improvement, climate, MIPAS, IASI, WALES sample preparation difficult

NO s, S, g(T) high temperature database, engine emissions

NO2 a(T, p) high temperature database, engine emissions

BrONO2 a(T, p) stratospheric Br budget and -chemistry sample preparation very difficult

N2O s, S, g, g2, d, LM Test of multispectrum fitting code

CH4 s, S, g, g2, d, LM NDACC (Network for the Detection of Atmospheric Composition Change)

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

N2O: line mixing in n3 rovibrational band

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0,0

0,5

1,0

0.081 %

0.086 %

0.076 %

tran

smitt

ance

103.7 mb, 205.9 mb; 498.2 mb; 1000.2 mb

0.074 %

-0,40,00,4

0.036 %

0.053 %

0.061 %

0.049 %

-0,40,00,4

(ob

s - ca

lc) *

100

-0,40,00,4

-0,40,00,4

-0,40,00,4

-0,40,00,4

Voigt - profile:

(ob

s - ca

lc) *

100

qSDV+LM - profile:

-0,40,00,4

2190 2200 2210 2220 2230 2240 2250

-0,40,00,4

wavenumber (cm-1)

0,0

0,5

1,0

0.081 %

0.086 %

0.076 %

tran

smitt

ance

103.7 mb, 205.9 mb; 498.2 mb; 1000.2 mb

0.074 %

-0,40,00,4

0.036 %

0.053 %

0.061 %

0.049 %

-0,40,00,4

(ob

s - ca

lc) *

100

-0,40,00,4

-0,40,00,4

-0,40,00,4

-0,40,00,4

Voigt - profile:

(ob

s - ca

lc) *

100

qSDV+LM - profile:

-0,40,00,4

2240,4 2240,8 2241,2 2241,6 2242,0

-0,40,00,4

wavenumber (cm-1)

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

H2O: Linestrength intercomparison in 1 µm region

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• NIST: cavitiy ringdown by Joseph T. Hodges• HIT: HITRAN 2008, mainly experimental data by Robert A. Toth• Excellent agreement DLR-NIST, mostly < 1 %• HITRAN2008 shows bias and large scatter

H2O linestrengths

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

10580 10600 10620 10640 10660 10680 10700 10720 10740

Wavenumber (cm-1)

rela

tiv

e d

iffe

ren

ce

(%

)

NIST vs DLR

HIT vs DLR

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

H2O: Linestrength intercomparison in 1 µm region

DLR.de • Chart 12

• Lodi: ab initio calculations• Good agreement for 2 0 1 0 0 0 and 0 0 3 0 0 0 with occasional outliers• Entire subbands shifted: 1 2 1 0 0 0 , 3 0 0 0 0 0, 1 0 2 0 0 0 up to 8 %

Average differences

1 2 1 0 0 0 4.1%2 0 1 0 0 0 0.0% 3 0 0 0 0 0 4.0% 1 0 2 0 0 0 -7.6%0 0 3 0 0 0 -0.1%

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

Red: residuals DLR, pink: residuals HITRAN 2008

H2O: IASI retrieval improvements in H2O n2 region using DLR linestrength and pressure broadening parameters

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Plots provided by S.A. Clough

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

BrONO2: New absorption cross sections

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• Q-branch peak intensity increases by 50 % from 296 K to 203 K• Cross sections measured with 0.025 cm-1 resolution• High resolution measurements @0.0017 cm-1 recorded at 296 K and 223 K, showing resolved

features

802.5 803.0 803.5 804.0 804.50

200

400

-ln(t) x

T /

p

Wavenumber/cm-1

293 K 273 K 253 K 233 K 203 K

> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014

Summary and current work

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• Laboratory equipment for measurements of stable and unstable species from FIR to UV at atmospheric pressures and temperatures

• Data reduction software including various quality assessment procedures• Emphasis on defined error bars

• DFG-project• H2O & CH4 in 1750-4000 cm-1 spectral range• Application in ground based solar occultation atmospheric measurements

• ESA-project: SEOM-Improved Atmospheric Spectroscopic Databases (IAS)• TROPOMI on Sentinel-5 Precursor• Improve CH4, H2O, CO in the 2.3 µm region• Resolve discrepancy of O3 in the UV/10 µm regions• Improve SO2 in the UV