Observational constraints on the efficiency of dehydration mechanisms in the tropical tropopause layer. Issue 6 (19th March 2016)

• Record Type: Journal Article
• Authors: Rollins, A. W.; Thornberry, T. D.; Gao, R. S.; Woods, S.; Lawson, R. P.; Bui, T. P.; Jensen, E. J.; Fahey, D. W.
• Is Part Of: Geophysical research letters. Volume 43:Issue 6(2016)
• Page Start: 2912
• Page End: 2918
• Publication Date: 2016-03-19
• Subjects: cirrus -- dehydration -- TTL -- stratospheric water vapor; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL067972
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The efficiency of dehydration in the tropical tropopause layer (TTL) determines how closely water vapor will be reduced to the lowest saturation mixing ratio encountered along a trajectory to the stratosphere, thereby strongly influencing stratospheric humidity. The NASA Airborne Tropical Tropopause Experiment (ATTREX) provided an unprecedented number and quality of in situ observations to constrain the key mechanisms controlling this dehydration. Statistical analyses of the ATTREX data show that nucleation, growth, and sedimentation each result in TTL dehydration becoming increasingly inefficient at temperatures below 200 K. Because of these inefficiencies, models that ignore these mechanisms likely underestimate water vapor at the stratospheric entry point by ~10–20% at the lowest temperatures. Key Points: New data set of TTL water and cirrus microphysical observations Ice nucleation, growth, and sedimentation are important limiting factors in dehydration Dehydration efficiency decreases with temperature below 200 K