laboratory spectroscopy at dlr
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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
DLR.de • Chart 3
• 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
DLR.de • Chart 10
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
DLR.de • Chart 11
• 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
DLR.de • Chart 13
Plots provided by S.A. Clough
> 2014 GEISA Workshop > J. Loos • Laboratory spectroscopy at DLR > 03.06.2014
BrONO2: New absorption cross sections
DLR.de • Chart 14
• 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
DLR.de • Chart 15
• 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
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