Greenhouse Gas Measurements from the Tropospheric Emission

Spectrometer (TES)by Ray Nassar (ray@io.harvard.edu), Jennifer Logan, Helen Worden and the TES Team

Ozone (O3)

TES on Aura• TES is a Fourier transform spectrometer that measures infrared emission of the atmosphere with an emphasis on the troposphere. • It is one of four science instruments on the Aura satellite, launched on 2004 July 15.• TES makes nadir observations from a 705 km sun-synchronous near-polar orbit.• Its nadir footprint is 5.3 km x 8.3 km and it obtains a global survey of the Earth in 16 orbits (~26 hours) and global coverage in 16 days.

Radiative Forcing

The net mean annual radiative forcing (RF) (best estimate value and probable range) up to the year 2005 [IPCC, 2007] are shown on the right. The direct radiative forcing of CO (not shown) is 0.024 Wm-2.

Version 002 R2971 Seq0100 Scn003

Hohenpeissenberg (48N, 11W)2005-07-18

Initial guessTES retrievalSondeSonde with TES op

xsondeTESop = xprior + ATES[xsonde-xprior]

• Approximately 1600 TES/sonde pairs with coincidence criteria of 300 km radius, ±9 hours (October 2004 - October 2006).• TES v002 nadir ozone profiles typically have a positive bias of 3-10 ppbv (~5-15%) in all latitude zones relative to ozonesondes (after removing flagged profiles and applying a cloud filter). • Good linearity in TES vs. sonde correlations, therefore relative variations in ozone measured by TES are meaningful.• High variability is related to atmospheric variability so an upper limit for of 7-16 ppbv.• R. Nassar, et al. (2007), Validation of Tropospheric Emission Spectrometer (TES) Nadir Ozone Profiles Using Ozonesonde Measurements, JGR submitted.• Also N. Richards et al. (2007), Validation of TES Ozone Profiles with Aircraft Observations During INTEX-B, JGR submitted.

Ocean near Galapagos islands 2006 July 16,

4.16ºS, 91.97ºW

DOFS = 1.48, H = 1.46

Alluvial sand in Saudi Arabia 2006 July 16, 21.38ºN,

47.10ºE

DOFS = 1.85, H = 3.94

Initial guess/priorTES retrievalTES error range

Future Plans for CH4

• Validate with ACE-FTS and DACOM.

• Compare with SCIAMACHY and GEOS-Chem distributions.

• Calculate radiative forcing?

• Source/Sink Inversions?0

30

60

Water (H2O)• Positive bias of 5-40% compared with the Cryogenic Frostpoint Hygrometer (CFH) and 5-15% compared with Radiosondes (RS).

• M. Shepherd et al. (2007), Comparison of Tropospheric Emission Spectrometer (TES) Water Vapor Retrievals with In Situ Measurements, submitted.

Carbon Monoxide (CO)• Validation using Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) and Differential Absorption CO Measurements (DACOM).

• C.P. Rinsland et al. (2007), JGR submitted.

• M. Luo et al. (2007), JGR submitted. Green line – difference if AK not used

O3 Radiative Forcing

• Use TES spectra along with retrieved surface and cloud properties, and ozone profiles to investigate Outgoing Longwave Radiation (OLR) sensitivity.• Integrate radiance spectra over the strong ozone band at 985-1080 cm-1 to obtain radiative forcing.• At present, only carried out for observations over oceans and with cloud free conditions. • To understand the contributions in a spectral region from ozone, water, and sea surface temperature (SST), a singular vector decomposition (SVD) is carried out. Water and ozone are mostly orthogonal. • TES total annual average ozone forcing = 0.48 ± 0.13 W/m2 (with = 0.24 W/m2) for 45°S to 45°N.• Worden, H. M., K. W. Bowman, J. R. Worden, A. Eldering, A Satellite Perspective of Tropospheric Ozone as a Greenhouse Gas, soon to be submitted.

B. Fisher

Methane (CH4)• Currently have a beta version of the data product. The ‘science ready’ release is still undergoing development.

• Profiles have some vertical information (typically ~1.5 but sometimes ~2.0 degrees of freedom).

• Peak sensitivity in mid to upper troposphere, but depends on surface type (thermal contrast).

• Will improve profile shape by revisiting microwindow selection, developing and applying a better a priori and/or initial guess, or correlating levels in the lower and upper troposphere.

DJF 2005-2006 MAM 2006

SON 2006JJA 2006

W/m

2W

/m2

W/m

2W

/m2

3-4 DOFS

TES Transect

Error

Precision

LOSU = Level Of Scientific Understanding