Measurements of the isotopic composition of ice and vapor above a tropical convective system
Abstract
We present observations of the isotopic composition of condensed and vapor water in the lower tropical tropopause layer (TTL) above a large summertime tropical convective system obtained by the Hoxotope and ICOS isotope instruments flown on the NASA WB-57 during TC4. A simple ice isotopic physics model is used in conjunction with our observational data to determine the origin of the condensed phase encountered above the cloud top. Regions of ice that are characteristic of both convective lofting, where the ice is isotopically heavier than the surroundings, and in situ condensation, where the ice shows little difference in isotopic composition with respect to the vapor, are encountered above the convective cell with convective lofting being the dominant mechanism by which water is transported to this altitude. While ice lofting is an important component of water transport models in the TTL, the isotopic composition of ice has been a relatively unconstrained parameter. Observations of condensed isotopes coupled with the vertical profile of vapor in the summertime TTL suggests that there is a seasonal variation in convective timescales that needs to be accounted for in convectively-influenced trajectory models describing the transport of water in the TTL.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A31D0130O
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud physics and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry