Session 3.1 The total hydrogen budget of the equatorial upper stratosphere

Monday, 8 June 2009: 1:50 PM
Pinnacle A (Stoweflake Resort and Confernce Center)
Jonathan E. Wrotny, Naval Research Laboratory, Washington D.C.; and G. E. Nedoluha, C. Boone, G. Stiller, and J. P. McCormack

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Water vapor and methane data measured by the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment (ACE), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) along with simulations from the NRL CHEM2D middle atmosphere model are used to study time series of H2O and CH4 in the equatorial upper stratosphere. Multi-year time series of equatorial upper stratospheric H2O+2*CH4 show temporal variations during periods of relative long-term stability in water vapor and methane entering the stratosphere. These variations, which are anti-correlated to CH4, are quasi-biennial and seasonal in nature, and peak near 2 hPa with a magnitude of 3 % of the H2O+2*CH4 mixing ratio. We find that β, or the ratio of the change in water vapor to the change in methane, is consistently >2 over the entire equatorial upper stratosphere in HALOE, ACE and MIPAS data. β values calculated from the CHEM2D model are similar, but slightly smaller, and this model shows that the quantity H2O+2*CH4+H2 is nearly conserved. We use this relationship to calculate molecular hydrogen mixing ratios from the observations. Multi-year average profiles of H2O+2*CH4 from HALOE, ACE, and MIPAS show an ~ 0.4 ppmv increase between 7 hPa and 1.5 hPa in the equatorial upper stratosphere, which we conclude must be offset by a decrease in molecular hydrogen, so that total hydrogen is nearly conserved. Collectively, these results illustrate the importance of the inclusion of molecular hydrogen in the hydrogen budget of the equatorial upper stratosphere.
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