Atmos. Chem. Phys. Discuss., 10, 25355-25388, 2010
© Author(s) 2010. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Estimate of bias in Aura TES HDO/H2O profiles from comparison of TES and in situ HDO/H2O measurements at the Mauna Loa Observatory
J. Worden1, D. Noone2, J. Galewsky3, A. Bailey2, K. Bowman1, D. Brown2, J. Hurley3, S. Kulawik1, J. Lee1, and M. Strong3
1Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA, USA
2University of Colorado, Boulder, CO, USA
3University of New Mexico, Albuquerque, NM, USA

Abstract. The Aura satellite Tropospheric Emission Spectrometer (TES) instrument is capable of measuring the HDO/H2O ratio in the lower troposphere using thermal infrared radiances between 1200 and 1350 cm−1. However, direct validation of these measurements is challenging due to a lack of in situ measured vertical profiles of the HDO/H2O ratio that are spatially and temporally co-located with the TES observations. From 11 October through 5 November 2008, we undertook a campaign to measure HDO and H2O at the Mauna Loa observatory in Hawaii for comparison with TES observations. The Mauna Loa observatory is situated at 3.1 km above sea level or approximately 680 hPa, which is approximately the altitude where the TES HDO/H2O observations show the most sensitivity. Another advantage of comparing in situ data from this site to estimates derived from thermal IR radiances is that the volcanic rock is heated by sunlight during the day, thus providing significant thermal contrast between the surface and atmosphere; this thermal contrast increases the sensitivity to near surface estimates of tropospheric trace gases. The objective of this inter-comparison is to better characterize a bias in the TES HDO data, which had been previously estimated to be approximately 5% too high for a column integrated value between 850 hPa and 500 hPa. We estimate that the TES HDO profiles should be corrected downwards by approximately 4.1% and 5.6% for Versions 3 and 4 of the data, respectively. These corrections must account for the vertical sensitivity of the TES HDO estimates. We estimate that the uncertainty of this bias correction is approximately 1%. However, future comparisons of TES data to other sensors are needed to refine this bias estimate because these uncertainties are primarily derived from only three sets of measurements.

Citation: Worden, J., Noone, D., Galewsky, J., Bailey, A., Bowman, K., Brown, D., Hurley, J., Kulawik, S., Lee, J., and Strong, M.: Estimate of bias in Aura TES HDO/H2O profiles from comparison of TES and in situ HDO/H2O measurements at the Mauna Loa Observatory, Atmos. Chem. Phys. Discuss., 10, 25355-25388, doi:10.5194/acpd-10-25355-2010, 2010.
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