11 Collisional effects on spectral shapes and remote sensing H. Tran LISA, CNRS UMR 7583,...
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1 Collisional effects on spectral shapes and remote sensing H. Tran LISA, CNRS UMR 7583, Université Paris-Est Créteil and Université Paris Diderot HiResMIR@CAES-Frejus-2013
11 Collisional effects on spectral shapes and remote sensing H. Tran LISA, CNRS UMR 7583, Université Paris-Est Créteil and Université Paris Diderot HiResMIR@CAES-Frejus-2013
11 Collisional effects on spectral shapes and remote sensing H.
Tran LISA, CNRS UMR 7583, Universit Paris-Est Crteil and Universit
Paris Diderot HiResMIR@CAES-Frejus-2013
Slide 2
22 Outline Introduction: Atmospheric observation and spectral
shape Isolated line : - The Doppler, Lorentzian and Voigt profiles
- Limits of the Voigt profile - Laboratory studies - Influence on
atmospheric retrieval Line-mixing for closely spaced lines -
Line-mixing effects - Laboratory studies - Influence on
spectroscopic data extraction - Influence on atmospheric retrieval
Conclusions HiResMIR@CAES-Frejus-2013
Slide 3
33 Measured spectra (satellite, balloon, ground,) - P, T
profiles - Molecule mole fraction profiles - Cloud altitude,
aerosol - etc. Input spectroscopic data (Position, Intensity,
spectral shape,) Spectral shapes Collisional (pressure) effects on
the spectral shape Radiative transfer Forward model Introduction:
Atmospheric retrievals HiResMIR@CAES-Frejus-2013
Slide 4
44 Pressure DopplerDoppler+CollisionCollisions
GaussienVoigtLorentzian Comparaison between the Gaussian, the
Lorentz and the Voigt profiles. Introduction: The Voigt profile
HiResMIR@CAES-Frejus-2013
Slide 5
55 Bernath et al., GRL, 32, L15S01 (2005) ACE spectra at
different tangent altitudes (1-0) R(0) 3 R(9) Introduction:
isolated lines and closely spaced lines
HiResMIR@CAES-Frejus-2013
Slide 6
66 Isolated lines HiResMIR@CAES-Frejus-2013
Slide 7
77 Measured and adjusted spectra using the Voigt profile. H 2
O/N 2, 3 band, 11 1,11 10 1,10 11 0,11 10 0,10 Limits of the Voigt
profile HiResMIR@CAES-Frejus-2013
Slide 8
88 Limits of the Voigt profile HiResMIR@CAES-Frejus-2013 It
neglects: 1.The velocity changes induced by collisions. The
detailed balance: change from v to v v. reduction of the Doppler
broadening Dicke narrowing effect 2.The speed-dependences of the
collisional width (v) and shift (v) of the line. This also (in
general) leads to a narrowed line
Slide 9
99 - For the velocity changes effect: The Galatry (soft
collisions) and Rautian (hard collisions) line-shapes. Introducing
a parameter VC (or ) - the velocity changing collisions frequency.
- For the speed dependences of the line-width and shift: The
speed-dependent Voigt profile, assuming a simple quadratic
dependence on the absolute speed or polynomial dependence on the
relative speed Simple and widely used non-Voigt approaches
HiResMIR@CAES-Frejus-2013
Slide 10
10 In situ absorption spectrum of tropospheric H 2 O recorded
by balloonborne diode laser and its fits using the Voit profile and
the Hard Collision profile Durry et al, JQSRT 94, 387,2005
Influence of non-Voigt effects on atmospheric retrievals
HiResMIR@CAES-Frejus-2013
Slide 11
11 Barret et al, JQSRT 95, 499, 2005 HF profile retrieved from
ground-based absorption FTIR measurements (Jungfraujoch station) in
the (1-0) R(1) micro-window by using the Voigt profile and the Soft
Collision model, compared with the HALOE profiles smoothed.
Influence of non-Voigt effects on atmospheric retrievals
HiResMIR@CAES-Frejus-2013
Slide 12
12 (Diode laser) Measured absorption of pure H 2 O (left) and H
2 O in air (right) and their differences with those adjusted using
the VP, HC, and SDVP HC Influence of non-Voigt effects on line
parameters determination HiResMIR@CAES-Frejus-2013
Slide 13
13 Ratios of the self-broadening coefficients and intensity
obtained by the HC (o) and SDVP ( ) to those obtained by the VP,
for 13 H 2 O lines in the near-infrared. Influence of non-Voigt
effect on line parameters HiResMIR@CAES-Frejus-2013
Slide 14
14 VC rate in red (SC) Rohart et al, J Mol Spectrosc 251, 282,
2008 Dependence of VC on pressure Relaxation of the 317.2 GHz line
of O 3 in collision with O 2 at 240 K. Remaining problems with
these non-Voigt approaches HiResMIR@CAES-Frejus-2013 Need to take
into account both Dicke and speed dependence effects
Slide 15
15 2 limits Hard collision model Soft collision model : memory
parameter KS more realistic than these two extreme cases and more
suitable for intermediate cases Velocity changing by the Keilson
and Storer model HiResMIR@CAES-Frejus-2013
Slide 16
16 With the model we compute the line shape. Then we fit the
calculated spectra (as the measured ones) by Voigt profiles and
look at the residuals. Pure H 2 O, 296K, 2 1 + 2 + 3 band:
measured, calculated 6 06 7 07 5 15 4 14 Model-experiment
comparison : pure H 2 O HiResMIR@CAES-Frejus-2013
Slide 17
17 H 2 O/N 2, 296K, 3, 11 111 10 110, 11 011 10 010 doublet H 2
O/air, 296K, 2 1 + 2 + 3, 5 15 4 14 line measured, calculated
Model-experiment comparison: H 2 O/air
HiResMIR@CAES-Frejus-2013
Slide 18
18 Model-experiment comparison: H 2 /N 2 Collisional width 296
K, Q(1) m = 0.92, 0 = 0.41 Bonamy et al., Eur. Phys. J. D, 2004 995
K, Q(1) m = 0.95, 0 = 0.50 HiResMIR@CAES-Frejus-2013
20 In some cases, for closely spaced lines, the Voigt profile
fails when P increases. It predicts shapes that are too broad.
Collisions induce transfers of populations between the levels of
the two lines that lead to transfers of intensity between the
lines. Line-mixing effects HiResMIR@CAES-Frejus-2013
Slide 21
21 Line-mixing effects: Absorption coefficient k populations d
k matrix element of radiation-matter coupling tensor L 0 matrix of
positions W relaxation operator. All effects of collisions.
Independent of within the impact approximation (not too far in the
wings) W lk 0 Line coupling between |k> and |l> W lk =0 No
line coupling (Lorentz ) HiResMIR@CAES-Frejus-2013
Slide 22
22 For moderate line overlapping, a first order perturbation
approach is possible. Then we only need to know one coupling
parameter (Y, related to the W matrix elements) per line
Line-mixing effects: Relaxation matrix HiResMIR@CAES-Frejus-2013
Relations for W
Slide 23
23 HiResMIR@CAES-Frejus-2013 Nadir looking instruments onboard
satellites Greenhouse gases Observation SATellite (GOSAT,
JAXA-NIES, in orbit) Orbiting Carbon Observatory (OCO 2, NASA)
MicroCarb (CNES, under study), CarbonSat (ESA, under study)
Spectral regions and aims - CO 2 from 1.6 m (weak) and 2.1 m
(strong) bands - Air mass from O 2 A band (0.76 m) - CH 4 from 2 3
band (near 1.7 m) - aerosols from CO 2 and O 2 bands
Detection/quantifying sinks and sources (1 ppm for x CO2, 0.3 %)
Extreme accuracy of spectra modelling. Huge constraints on the
spectroscopic data and the prediction of pressure effects
(collisions and spectral-shape) Line-mixing and remote sensing:
Monitoring GreenHouse Gases from space
Slide 24
24 Sza 79.9, Park Falls, region 2.1 m Wrong air-mass (and time)
dependences CO 2 retrieved Sza 79.9, Park Falls, region 1.6 m CO 2
: ground-based measurements HiResMIR@CAES-Frejus-2013
Slide 25
25 Sza 79.9, Park Falls, 1.27 m band Sza 79.9, Park Falls, A
band Wrong time (and air-mass) dependences O 2 : Ground-based
measurements HiResMIR@CAES-Frejus-2013
Slide 26
26 Spectra: air mass 5.7, Park Falls Wrong time and airmass
dependences Largely erroneous conclusions on sinks and sources CH 4
: Ground-based atmospheric solar absorption
HiResMIR@CAES-Frejus-2013
Slide 27
27 No use CO 2 bands: Scaling model, self consistent model for
all bands. Adjustment of model in 720 cm -1 Q branch. No use of
present NIR bands CH 4 : Semi-classical model. Self consistent
model for 3, 4 and 2 3 bands. Adjustment of model in 3 band at high
pressure. No use of present 2 3 band No use O 2 A-band: Scaling
model. Model developed from O 2 A band at elevated pressure. No use
of low pressure spectra Collision induced absorption: From analysis
of O 2 A band at elevated pressures Modeling of line-mixing effect
HiResMIR@CAES-Frejus-2013
Slide 28
28 O 2 /N 2 A band 76.0 atm 47.6 atm 28.1 atm ___ measurement,
___ Line-mixing ___ Lorentz CO 2 /N 2 Line-mixing effects:
Laboratory studies HiResMIR@CAES-Frejus-2013
Slide 29
29 Line-mixing effects: Influence on spectroscopic parameters
retrieval CH 4 /N 2, 2 3, R(6), 296 K
HiResMIR@CAES-Frejus-2013
Slide 30
30 12990130201305013080131101314013170 -0.05 0.00 0.05 0.10
0.15 observed-(LM+CIA) Residual wavenumber (cm ) -0.05 0.00 0.05
0.10 0.15 observed-Voigt 0.0 0.2 0.4 0.6 0.8 1.0 Transmission
Influence on retrievals: O 2 ground-based measurements
HiResMIR@CAES-Frejus-2013 Spectra: Sza 79.9, Park Falls O 2 A band
region O 2 A band: Relative errors on surface pressures retrieved
from atmospheric spectra
Slide 31
31 Fits of a ground based transmission spectra in the region of
the 2 1 + 3 band of CO 2 Significant errors (10%) on the CO 2
atmospheric amount. Sinks and sources !!! Influence on retrievals:
CO 2 ground-based measurements HiResMIR@CAES-Frejus-2013
Slide 32
32 Influence on retrievals: CH 4 ground-based measurements
Methane amounts retrieved from atmospheric spectra
HiResMIR@CAES-Frejus-2013
Slide 33
33 Jupiter ISO/SWS spectrum in the 4 band region of CH 4
Influence on planetary spectra HiResMIR@CAES-Frejus-2013
Slide 34
34 Summary Spectral shape has become a key issue for high
precision soundings (OCO, ACE, ) When line is isolated: - The Voigt
profile fails to model isolated line-shape -> need to take into
account Dicke narrowing and speed dependence effects (velocity
effects) - Influence of velocity effects on atmospheric retrieval
is quite small (but few studies available) When lines are closely
spaced (especially at high pressure): - line-mixing can be observed
- Increasing evidences of influence of line-mixing for remote
sensing - Need to take into account both line-mixing and velocity
effects HiResMIR@CAES-Frejus-2013