Greenhouse Gas Measurements from the Tropospheric Emission Spectrometer (TES) by Ray Nassar ([email protected]), Jennifer Logan, Helen Worden and the TES Team Ozone (O 3 ) 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 guess TES retrieval Sonde Sonde with TES op x sondeTESop = x prior + A TES [x sonde - x prior ] • 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/prior TES retrieval TES error range Future Plans for CH 4 • Validate with ACE-FTS and DACOM. • Compare with SCIAMACHY and GEOS-Chem distributions. • Calculate radiative forcing? 0 30 60 Water (H 2 O) • 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 O 3 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/m 2 (with = 0.24 W/m 2 ) 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 (CH 4 ) • 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 DJF 2005-2006 MAM 2006 SON 2006 JJA 2006 W/m 2 W/m 2 W/m 2 W/m 2 3-4 DOFS TES Transect Error Precision LOSU = Level Of Scientific Understandin g