Journal article
Ice nucleation and dehydration in the Tropical Tropopause Layer
Proceedings of the National Academy of Sciences - PNAS, Vol.110(6), pp.2041-2046
02/05/2013
DOI: 10.1073/pnas.1217104110
PMCID: PMC3568347
PMID: 23341619
Abstract
Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth's radiation budget and climate. Recent high-altitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: (i) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to similar to 70%) with respect to ice; and (ii) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L-1 (often less than 20 L-1), whereas the high ice concentration layers (with concentrations up to 10,000 L-1) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as similar to 1.7 times the ice saturation mixing ratio.
Details
- Title: Subtitle
- Ice nucleation and dehydration in the Tropical Tropopause Layer
- Creators
- Eric J. Jensen - Ames Research CenterGlenn Diskin - Langley Research CenterR. Paul Lawson - cSPEC, Inc., Boulder, CO 80301;Sara Lance - cSPEC, Inc., Boulder, CO 80301;T. Paul Bui - Ames Research CenterDennis Hlavka - Science Systems and Applications (United States)Matthew McGill - Goddard Space Flight CenterLeonhard Pfister - Ames Research CenterOwen B. Toon - Laboratory for Atmospheric and Space PhysicsRushan Gao - NOAA, Chem Sci Div, Earth Syst Res Lab, Boulder, CO 80305 USA
- Resource Type
- Journal article
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.110(6), pp.2041-2046
- DOI
- 10.1073/pnas.1217104110
- PMID
- 23341619
- PMCID
- PMC3568347
- NLM abbreviation
- Proc Natl Acad Sci U S A
- ISSN
- 0027-8424
- eISSN
- 1091-6490
- Publisher
- National Academy of Sciences
- Number of pages
- 6
- Grant note
- NASA Radiation Sciences Program; National Aeronautics & Space Administration (NASA) NASA Airborne Tropical Tropopause Experiment
- Language
- English
- Date published
- 02/05/2013
- Academic Unit
- Physics and Astronomy; Chemical and Biochemical Engineering
- Record Identifier
- 9984276451302771
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