TES methane: Recent validations and comparisons

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• TES methane Recent validations and comparisons
• Vivienne Payne, Mark Shephard, Janusz
  Eluszkiewicz, Karen Cady-Pereira
• Atmospheric and Environmental Research, Inc.
• Tony Clough
• Clough Radiation Associates
• Brendan Fisher, Greg Osterman, Bill Irion
• JPL
• Ray Nassar
• University of Toronto
• Jennifer Logan
• Harvard University
• TES Science Team Meeting
• 23rd-25th February 2009

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Overview

• Introduction to TES methane
• V04 vs V03
• Validation to date
• Planned validation
• Potential applications

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TES CH4 Averaging kernels and DOFS
Tropical, over ocean
Low latitude, over desert

• Antarctica (polar winter)

Siberia (polar summer)
TES is most sensitive to CH4 in mid to upper
troposphere.
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RTVMRs

• Representative Tropospheric Volume Mixing Ratio
• One value to represent CH4 in altitude region
  where TES is sensitive
• Reflects the information available in the TES CH4
  measurement
• Relatively insensitive to the prior
• Payne et al., (2009) JGR, in review

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Updates in V04 compared to V03

• Updated strategy for temperature and H2O
  retrievals
• Update to a priori constraints for CH4
• Ten latitude bands instead of five
• More realistic representation of variation of
  tropopause altitude
• Update to N2O climatology
• N2O is an interferant in the CH4 microwindows
• Increases of 0.25 per year based on NOAA
  ground-based measurements
• Impact of this change was small
• V04 values are generally 1 higher than V03
• V04 and V03 show the same large-scale features
• Although differences do vary somewhat with
  season/location
• An increase is not the direction that we would
  have liked.
• Influence of different factors listed above to be
  investigated.

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TES/GEOS-Chem comparisons
V03 (minus 3.5 bias)
V04 (minus 4.5 bias)
V04
V03
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DACOM flights for INTEX-B Comparisons between
DACOM, TES v004, AIRS v5.0

• DACOM Differential Absorption CO Measurement
• PI Glen Sachse, NASA Langley
• INTEX-B DACOM flights March/April/May 2006
• TES/AIRS
• Both mid-IR instruments, sensitive to CH4 in mid-
  to upper troposphere
• AIRS CH4 has already been compared with aircraft
  measurements from a range of latitudes
• Xiong et al, JGR-B (2008)
• Different spectral resolution
• TES 0.06 cm-1 unapodized
• AIRS 1.0 cm-1 in CH4 region
• Different forward models
• AIRS v5.0 CH4 absorption coefficients tuned using
  tropical aircraft profiles
• Different retrieval techniques
• Retrieval approach
• Retrieval grid

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TES/AIRS/DACOM comparisons example case

• Comparable sensitivity
• TES sensitive lower down
• TES has slightly more DOFS
• Helpful at high latitude
• TES biased high wrt DACOM
• Reasons for bias under investigation
• AIRS biased low wrt DACOM
• Plans to re-examine tuning in future versions

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TES/AIRS/DACOM scatter plots

• TES 3.7 bias wrt DACOM
• Investigate physical reasons for bias

AIRS -2 bias wrt DACOM Tuning to be
re-evaluated for v6.0
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NDACC FTIR comparisons(Network for the Detection
of Atmospheric Composition Change)
FTIR column data publicly available from
http//www.ndsc.ncep.noaa.gov/

• -77.825 166.65 Arrival Heights, Antarctica
• -45.038 169.684 Lauder, New Zealand
• 28.3 343.52 Izana, Tenerife
• 43.66 280.60 Toronto, Canada
• 53.107 8.854 Bremen, Germany
• 60.200 10.800 Harestua, Norway
• 67.84 20.41 Kiruna Sweden
• 76.52 291.24 Thule, Greenland
• 78.92 11.92 Ny-Aalesund, Spitsbergen
• 80.050 273.58 Eureka NDSC

Future work Comparisons with FTIR tropospheric
VMRs through collaboration with instrument teams.
A. Goldman (U. Denver), J. Hannigan (NCAR)
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FTIR comparisons

• Work with Jim Hannigan (NCAR) and Aaron Goldman
  (U. Denver)
• Start with Thule dataset
• Compare methane measurements in a representation
  where both instruments have sensitivity

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Reasons for the observed high bias?

• Investigate impact of adding methane line
  coupling
• Interfering species in TES microwindows N2O and
  H2O
• Influence of the cloud retrieval for this step?
• TSUR is 295 K for this case - dont see the
  surface here
• Offset in background could introduce a bias?

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Future validation work

• DACOM comparisons from ARCTAS
• Mid-tropospheric comparisons with the NDACC FTIRs
• Start with Thule dataset
• Global-scale comparisons with AIRS
• Do both instruments see the same large-scale
  features?
• Comparisons with SCIAMACHY?
• Further investigation of cause of the high bias
• TES methane validation paper

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Regional Transport Model

• WRF-STILT regional transport model
• Stochastic Time Inverted Lagrangian Transport
  (STILT) model (Harvard), descendant of HYSPLIT
• Driven by customized output from the Weather
  Research and Forecasting (WRF) model (improved
  mass conservation, inclusion of convective mass
  fluxes, analysis nudging) - maximum accuracy and
  meteorological realism
• Coupled with high-resolution a priori flux
  models, e.g., Kort et al. 2008 for CH4 and N2O,
  Miller et al. 2008 for CO (BRAMS instead of WRF
  to drive STILT)
• Receptor-orientated Lagrangian model ideal for
  source attribution and inversion work, provides a
  high-resolution lens to global models
• Development funded by multiple agencies (NASA,
  NOAA, NSF)
• Validation and Science Analysis
• Preliminary simulations of localized measurements
  give confidence in the models performance

Simulated CO2
Measured CO2
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Does TES See the Local Surface?
10-day mean
Altitude m AGL
Longitude deg W

• Local surface influences evident in selected
  cases (top left)
• Potential surface influences for a given receptor
  quantified by concentration footprints (top
  right)
• Adjoint
• Jacobian of concentration wrt surface fluxes
  units ppmv/(?mol/m2/s), weighted by the TES
  sensitivity function
• Convolution with a flux model necessary for
  quantitative comparisons
• Boundary conditions from global models
  (GEOS-Chem) or in-situ observations

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Constraints on methane fluxes

• Initial work with WRF-STILT over North America
• Possibilities for use of TES methane to constrain
  fluxes in other regions
• Wetland release (high latitude and tropical)
• Biomass burning
• Rice paddies
• Release from Artic permafrost
• Decaying gas hydrate deposits
• No measurements north of 70N after August 2008

High values here in September, all years Also
noted by AIRS team - Xiong et al. 2008
September 2007
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Summary

• V04 is higher than V03
• Validation is ongoing
• High bias of 3-5 in TES methane
• compared to aircraft meas. and GEOS-Chem
• Reasons for bias are under investigation
• Updates to consider for R12
• Line coupling?
• Choice of microwindows?
• Next link TES CH4 to fluxes

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Backup slides
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Global spatial features
TES (2006) minus GEOS-Chem (2001), after 3.5
bias removal
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TES CH4 representative tropospheric VMR
TES RTVMR minus GEOS-Chem 2001 RTVMR field (after
removal of 3.5 high bias from TES)
High CH4 over Indonesia in October 2006
associated with increased biomass burning during
the El Nino?
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Northern Hemisphere CH4
High CH4 values Possible sources? Transport
across Pacific?
TES CH4 RTVMR (July 2006)
Effective pressure
Difference from GEOS-Chem