1 TCCON at Caltech, May 2008
New Line Parameters for Near-IR Methane and the Oxygen A-Band
presented by
Linda R. Brown (JPL)
New Line Parameters for Near-IR Methane and the Oxygen A-Band
presented by
Linda R. Brown (JPL)
World-wide Effort Belgium, Canada, France, Germany, Netherlands,
Russia, Switzerland, United States
CH4: BOUDON et al., NIKITIN et al. , QUACK et al., FRANKENBERG et al.,
ANTONY et al., SMITH et al., PREDOI-CROSS et al., TRAN et al.KASSI et al., GAO et al., LIU et al.
O2: TRAN et al., PREDOI-CROSS et al., ROBICHAUD et al., BROWN et al.
JPL: Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA).
HITRAN 2008
METHANE: The PolyadsMETHANE: The Polyads
G
lob
al f
it
new
From Boudon et al. EGU 2008
1.7 μm
2.3 μm
HITRAN 2008
Much improved analyses using really cold dataMuch improved analyses using really cold data ►Near-IR spectra at 78 K permitted more Octad bands to be assigned.
►Higher order terms were added to Hamiltonian models for Global fit.
Doppler-limited spectra from a Bruker FTS in Zurich (M. Quack) 2700 - 8000 cm-1
Reduced energy
(cm-1) vs J: Many new
assignments found using cold (78 K)
spectra.
Modeling the line positions improved by factor of 10!
Better predicted spectrum
←Pentad
← Octad
Tetradecad
Isocad →
HITRAN 2008
12CH4 Global modeling: 0–4800 cm-112CH4 Global modeling: 0–4800 cm-1
Fit of effective Hamiltonian parameters: 16 738 data (MW, IR, Raman)
Polyad Ground State Dyad Pentad Octad Global
# Parameters in model 10 62 228 596 896
# Fitted parameters 10 53 188 496 747
dRMS / 10 3 cm 1 0.0017 0.13 0.59 3.49 2.64
Fit of effective dipole moment parameters
Transition Dyad - GS Pentad - Dyad Pentad - GS Octad - GS
# Parameters in model 7 20 29 95
# Fitted parameters 7 19 29 80
dRMS / % 3.38 5.19 3.01 9.64
# Data 1189 1578 2586 3262
Albert et al. (almost submitted)
HITRAN 2008
Octad: measured line intensitiesOctad: measured line intensities
top: Log of measured line intensities bottom: %(observed – calc)
NEED: More and better measurements of weak lines (including 13CH4)!
Needed to Needed to obtain obtain betterbetter
modelling modelling of line of line intensitiesintensities
HITRAN 2008
12CH4: 4800 - 6300 cm-1: formerly intractable Must assign and model 60 sub-vibrational bands
12CH4: 4800 - 6300 cm-1: formerly intractable Must assign and model 60 sub-vibrational bands
from Kassi et al. accepted
NEW Hope: FTS and CRDS spectra at 78 Kelvin.
▪ Quack et al.
FTS spectra at 78 K : line positions & assignments ▪ Liu et al., Gao et al., Kassi et al. CRDS: Intensities and empirical lower state energy 5852-6181 cm-1 ▪ Frankenberg et al. FTS spectra 5998 – 6130 cm-1 (with N2- pressure broadening)
Best hope for HITRAN 2008: USE EMPIRICAL LINELISTS?
Tetradecad
2ν3 good for ground-based
retrievals
↔ H2O ←4800 cm-1 6400
HITRAN 1992: Margolis 1988, 1990: 5500-6184 cm-1: 2684 stronger lines with many empirical lower states
HITRAN 2004: Brown 2005: line positions, weaker intensities: for 4800-5500, 6184 – 9200 cm-1
(empirical E″ lost in reformating)
HITRAN 2008
CH4: 6600 - 7700 cm-1: ~intractable region Must assign and model 134 sub-vibrational bands
CH4: 6600 - 7700 cm-1: ~intractable region Must assign and model 134 sub-vibrational bands
Cold spectra:
hope to see new assignments by
inspection!
or
Solve for empirical lower state energies using line intensities
measured
at different temperatures
Kassi, Gao, Romanini and Campargue (in press).
Q
3 2 1
Need theoretical modeling to understand assignments!
HITRAN 2008
Status of 12CH4 ParametersStatus of 12CH4 Parameters
Polyad / Spectral region Line positions Line intensities Line shape
1 – Ground state
0–200 cm-1 (> 50 m)
Complete analysis,
J ≤ 24Few measurements to confirm analysis
2 – Dyad1000–1800 cm-1 (5.6–10.0 m)
Complete analysis,
J ≤ 23Complete analysis
with 9 hot bandsOld & New
measurements
3 – Pentad
2200–3300 cm-1 (3.0–4.6 m)
Complete analysis,
J ≤ 18Cold band ok; few hot band intensities
Old meas. &
New theory ν3 only
4 – Octad
3700–4800 cm-1 (2.0–2.7 m)
Good analysis,
Cold bands J ≤ 17~ Better analysis, cold bands only
~ 1100 air- widths and shifts
5 – Tetradecad
5400–6300 cm-1 (1.6–1.9 m)
Incomplete analysis,
J ≤ 10Partial analysis, cold bands only
A few hundred new measurements
6 – Icosad
6600–7700 cm-1
partial analysis
of 1 band?measurements
but No prediction
Upper polyads
> 7800 cm-1 (< 1.28 m)? ?
HITRAN 2008
Methane Work in ProgressMethane Work in Progress
HITRAN 2008
New Pressure Broadening for MethaneNew Pressure Broadening for Methane
• 7 μm: measured widths, shifts, temp. depend., Line mixing Benner, Devi, Predoi-Cross, Smith….. - in prep.
• 3.3 μm ν3: theoretical calculation of widths, shifts and temperature dependence of widths for A and F
Antony et al. J. Mol. Spectrosc. in press • 1.6 μm N2-widths and shifts of stronger lines above 5998 cm-1
Frankenberg et al. Atmos. Chem. Phys.-accepted.
• Line mixing: weak but needed in atmospheric retrievals: Smith et al. (poster) v4
Tran et al. JQSRT 2006 v4 and v3
Predoi-Cross et al. JMS 2007 v2+v3
Mondelain et al. 2007, 2008 P9 of v3 : temp dependence= 1.2 – 1.5
HITRAN 2008
Line mixing calculations for methaneLine mixing calculations for methane
HITRAN 2008
LINE MIXING + REQUIREDLINE MIXING + REQUIREDMondelain et al. 2008: Atmospheric spectra►Measured and calculated transmissions at a tangent height of ~ 18 km.
► Fitting residuals (observed–calculated) are (from top to bottom)
1) Voigt model with HITRAN values
2) Voigt model with their new line mixing 3) Voigt model with their new temperature dependence exponent4) a hard model without line mixing (using their new values) 5) a hard model (Rautian) with line mixing and their new temperature dependence exponents.
Need Line mixing (Rosenkranz) ζ
and Dicke Narrowing β
HITRAN 2008
Methane for HITRAN 2008 under constructionMethane for HITRAN 2008 under construction
REGION (cm-1) NEW POSITIONS AND INTENSITIES
0 - 4800: 12CH4 global fit
– (nothing new for 13CH4)
3300- 3700: CH3D (and maybe at 6600 cm-1)
4800- 7700: lots of work in progress, but not ready NEW Voigt Broadening Parameters
Apply ν3 calculated widths and temp. dep
Then replace with available measurements
New N2-broadening at 1.66 um + ???
(3000 out of 250000 transitions) Estimate shifts and use limited measurements Line mixing: tbd ??
HITRAN 2008
Oxygen A - Band at 760 nm (13122 cm-1)Oxygen A - Band at 760 nm (13122 cm-1)
New effort by Tran & Hartmann: Still Ordinary Voigt Full W-matrix Line mixing but with different line broadening parameters used empirical expression for widths
from Yang et al. 2005
Revised Collision Induced Absorption (CIA)
But still a problem:
Can’t retrieve right O2 abundance inaccurate line parameters? missing isotopes? wrong line shapes?
(a) Ground-based Atmospheric spectra
Park Falls FTS (P. Wennberg)
Voigt only : LINE MIXING REQUIRED!!!
(b) Tran et al. JGR-Atmos 2006
(c) New: Tran and Hartmann
( in press)
HITRAN 2008
HITRAN 2008
Oxygen A - Band at 760 nm using NIST CRDS (Joe Hodges) Line intensities and positions of P branch retrieved with Galatry profile:Oxygen A - Band at 760 nm using NIST CRDS (Joe Hodges) Line intensities and positions of P branch retrieved with Galatry profile:
Should lower calculated intensities:
Compared to HITRAN 2004:
NIST CRDS is -0.8%
Average of 9 studies is -1.3%
(how much of this difference is due to
the different line shapes used?)
HITRAN line positions (B&P) are within 0.0007 cm-1 of NIST calibrated measurements.
NIST/Caltech/JPL: Robichaud et al. 2008
Intensities measured with NIST samples
Line positions calibrated with atomic K transitions
With accuracies better than 0.00005 cm-1
30 MHz = 0.001 cm-1
Ratio of Ints. Others/HITRAN
HITRAN 2008
Oxygen A - Band at 760 nm Air-widthsOxygen A - Band at 760 nm Air-widths
Different line shapes produce different values of air-widths:
Red: line mixing with speed dependence
Green: Voigt with Dicke Narrowing &
No line mixing (NIST CRDS)
Blue: Voigt with line mixing
Which set gives the best accuracies?
Above: Robichaud et al. 2008
Air-widths: refit to Yang empirical eq.
HITRAN 2008
O2 Pressure shifts: uncertain because of
calibration of wavenumber scale and/or line shape choices?
O2 Pressure shifts: uncertain because of
calibration of wavenumber scale and/or line shape choices?
Alternative to Voigt profiles
Dicke narrowing?
Speed dependence?
Need consensus about best line shape!
Ciurylo and Szudy, JQSRT 1997
From Predoi-Cross in press
HITRAN 2008
Isotopologues of the Oxygen A - Band at 760 nm Isotopologues of the Oxygen A - Band at 760 nm
60
40
20
0
cavi
ty lo
sses
, ppm
13055130501304513040wavenumbers, cm
-1
16O2
16O17O
16O18O
17O18O
18O2
20 18
21 20 19 18
21 20 19 18
22 21 20 19
22 20
60
40
20
0
cavi
ty lo
sses
, ppm
13055130501304513040wavenumbers, cm
-1
16O2
16O17O
16O18O
17O18O
18O2
20 18
21 20 19 18
21 20 19 18
22 21 20 19
22 20
Work in progress at NIST/Caltech (Robichaud et al. in prep.)
Isotopologues measured with enriched samples using CRDS
Positions, many intensities and some “self-broadened” line widths
New results for 16O18O and 16O17O will be provided to HITRAN with broadening from the main isotope applied.
HITRAN 2008
Oxygen A - Band at 760 nm Weak line mixing: first order coefficients
Oxygen A - Band at 760 nm Weak line mixing: first order coefficients
Left: measured with
speed dependence Voigt vs Voigt
Predoi-Cross et al. in press
Tran and Hartmann in press
Measured using
Speed depend.
Voigt
or Voigt
R & P similar to Q at each m
Black: ECS calculated mixing
Gray: Measured Predoi-Cross et al.
HITRAN 2008
Oxygen A - Band at 760 nm New effort with Kitt Peak FTS lab spectra:
Oxygen A - Band at 760 nm New effort with Kitt Peak FTS lab spectra:
Combine Kitt Peak FTS lab data from Brown and Plymate (2000) with new higher pressure scans up to ~ 3 atm.
Brown, Pine, Miller
Best fit using
Rautian (narrowing) with
weak line mixing
HITRAN 2008
O2: test with synthetic spectra at infinite resolutionO2: test with synthetic spectra at infinite resolution
Lower panels are differences between top and other calculated spectra (offset by successive increments of - 0.2) --------------------------------------------Green: shows Pine’s software computes the same spectrum as Tran’s code
Rust: only Voigt used.
Teal: difference with W-matrix and Rosenkranz line mixing
Purple: Rosenkranz line mixing adjusted to match the top spectra
Brown: 4 other synthetic spectra o were computed at different gas conditions and fitted as test data using multi-spectrum fitting.
Didn’t quite match R branch band head.
Voigt inadequate!
Rosenkranz: good enough for atmosphere?
Black: synthetic spectrum calculated by Pine using Tran et al. 2006 code Line mixing is full “w” matrix.
Pressure = 1 atm of air; path = 1 km
HITRAN 2008
O2 A-band for HITRAN 2008: O2 A-band for HITRAN 2008:
Positions: use Robichaud et al. (NIST-CRDS): isotopes too
Intensities: scale using Robichaud et al. or average of many: ±0.5%
Widths: empirical expression Robichaud or Predoi-Cross model Shifts: ???????? Dependences on line shape model
Dicke narrowing (Robichaud et al. 2008 or Predoi-Cross et al. 2008) Temp. dependence of widths, shifts, mixing, narrowing: ???
Line mixing ????
Tran and Hartmann 2008 or Predoi-Cross et al. 2008
CIA: Trans and Hartmann (2008)
