The isotopic composition of near-surface water vapor at the Maido observatory (Reunion Island, southwestern Indian Ocean) documents the controls of the humidity of the subtropical troposphere - fdi:010071408 - Horizon

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Guilpart E., Vimeux Françoise, Evan S., Brioude J., Metzger J. M., Barthe C., Risi C., Cattani O. (2017). The isotopic composition of near-surface water vapor at the Maido observatory (Reunion Island, southwestern Indian Ocean) documents the controls of the humidity of the subtropical troposphere. Journal of Geophysical Research : Atmospheres, 122 (18), 9628-9650. ISSN 2169-897X

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Lien direct chez l'éditeur doi:10.1002/2017jd026791

Titre
The isotopic composition of near-surface water vapor at the Maido observatory (Reunion Island, southwestern Indian Ocean) documents the controls of the humidity of the subtropical troposphere
Année de publication2017
Type de documentArticle référencé dans le Web of Science WOS:000416388000006
AuteursGuilpart E., Vimeux Françoise, Evan S., Brioude J., Metzger J. M., Barthe C., Risi C., Cattani O.
SourceJournal of Geophysical Research : Atmospheres, 2017, 122 (18), p. 9628-9650. ISSN 2169-897X
RésuméWe present a 1 year long record of the isotopic composition of near-surface water vapor (delta O-18(v)) at the Maido atmospheric observatory (Reunion Island, Indian Ocean, 22 degrees S, 55 degrees E) from 1 November 2014 to 31 October 2015, using wavelength-scanned cavity ring down spectroscopy. Except during cyclone periods where delta O-18(v) is highly depleted (-20.5%), a significant diurnal variability can be seen on both delta O-18(v) and q(v) with enriched (depleted) water vapor (mean delta O-18(v) is -13.4% (-16.6%)) and moist (dry) conditions (mean q(v) is 9.7 g/kg (6.4 g/kg)) during daytime (nighttime). We show that d18Ov diurnal cycle arises from mixing processes for 65% of cases with two distinct sources of water vapor. We suggest that delta O-18(v) diurnal cycle is controlled by an interplay of thermally driven land-sea breezes and upslope-downslope flows, bringing maritime air to the observatory during daytime, whereas at night, the observatory is above the atmospheric boundary layer and samples free tropospheric air. Interestingly, delta O-18(v) record also shows that some nights (15%) are extremely depleted (mean delta O-18(v) is -21.4%). They are among the driest of the record (mean q(v) is 2.9 g/kg). Based on different modeling studies, we suggest that extreme nocturnal isotopic depletions are caused by large-scale atmospheric transport and subsidence of dry air masses from the upper troposphere to the surface, induced by the subtropical westerly jet.
Plan de classementHydrologie [062] ; Sciences du milieu [021]
Descr. géo.REUNION ; OCEAN INDIEN ; MAIDO MONT ; ZONE SUBTROPICALE
LocalisationFonds IRD [F B010071408]
Identifiant IRDfdi:010071408
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010071408

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