Hydration, dehydration, and the total hydrogen budget of the 1999/2000 winter Arctic stratosphere

• Published in: Journal of Geophysical Research. D. Atmospheres 2002-03, Vol.107 (D5), p.SOL 63-1-SOL 63-12
• Main Authors: Herman, R. L., Drdla, K., Spackman, J. R., Hurst, D. F., Popp, P. J., Webster, C. R., Romashkin, P. A., Elkins, J. W., Weinstock, E. M., Gandrud, B. W., Toon, G. C., Schoeberl, M. R., Jost, H., Atlas, E. L., Bui, T. P.
• Format: Article
• Language: English
• Subjects: Arctic; Atmospheric composition. Chemical and photochemical reactions; dehydration; Earth, ocean, space; Exact sciences and technology; External geophysics; hydration; Physics of the high neutral atmosphere; SOLVE; stratosphere; water
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2001JD001257

Stratospheric H2O, CH4, and H2 measured during the 1999/2000 Arctic winter are used to examine the total hydrogen budget and to quantify hydration and dehydration within the Arctic polar vortex. The mean volume mixing ratio of equivalent water, H2Oeq = H2O + 2*CH4, was found to be 7.38 ± 0.11 ppmv in the vortex and 7.35 ± 0.10 ppmv in the extravortex and vortex edge regions, implying insignificant net loss of H2O from the 50–90 hPa layer of the Arctic stratosphere. However, isolated occurrences of hydration and dehydration were observed on several flights. In particular, an average dehydration of 0.31 ppmv was encountered for 440 km along the NASA ER‐2 aircraft flight path on 27 January 2000 (0.63 ppmv maximum dehydration). Diabatic back‐trajectory calculations indicate that this dehydrated air parcel may have encountered temperatures below the ice frost point two weeks earlier. In addition to these isolated events, measurements of equivalent water indicated a decrease with altitude throughout the lower stratospheric vortex and vortex edge. Potential causes of this altitude dependence are quantified.