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Physical Processes Controlling the Spatial Distributions of Relative Humidity in the Tropical Tropopause Layer over the PacificThe spatial distribution of relative humidity with respect to ice (RHI) in the boreal wintertime tropical tropopause layer (TTL, is asymptotically Equal to 14-18 km) over the Pacific is examined with the measurements provided by the NASA Airborne Tropical TRopopause EXperiment. We also compare the measured RHI distributions with results from a transport and microphysical model driven by meteorological analysis fields. Notable features in the distribution of RHI versus temperature and longitude include (1) the common occurrence of RHI values near ice saturation over the western Pacific in the lower to middle TTL; (2) low RHI values in the lower TTL over the central and eastern Pacific; (3) common occurrence of RHI values following a constant mixing ratio in the middle to upper TTL (temperatures between 190 and 200 K); (4) RHI values typically near ice saturation in the coldest airmasses sampled; and (5) RHI values typically near 100% across the TTL temperature range in air parcels with ozone mixing ratios less than 50 ppbv. We suggest that the typically saturated air in the lower TTL over the western Pacific is likely driven by a combination of the frequent occurrence of deep convection and the predominance of rising motion in this region. The nearly constant water vapor mixing ratios in the middle to upper TTL likely result from the combination of slow ascent (resulting in long residence times) and wave-driven temperature variability. The numerical simulations generally reproduce the observed RHI distribution features, and sensitivity tests further emphasize the strong influence of convective input and vertical motions on TTL relative humidity.
Document ID
20170010359
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1002/2017JD026632
Authors
Jensen, Eric J. (NASA Ames Research Center Moffett Field, CA, United States)
Thornberry, Troy D. (National Oceanic and Atmospheric Administration Boulder, CO, United States)
Rollins, Andrew W. (National Oceanic and Atmospheric Administration Boulder, CO, United States)
Ueyama, Rei (Bay Area Environmental Research Inst. Moffett Field, CA, United States)
Pfister, Leonhard (NASA Ames Research Center Moffett Field, CA, United States)
Bui, Thaopaul (NASA Ames Research Center Moffett Field, CA, United States)
Diskin, Glenn S. (NASA Langley Research Center Hampton, VA, United States)
Digangi, Joshua P. (NASA Langley Research Center Hampton, VA, United States)
Hintsa, Eric (National Oceanic and Atmospheric Administration Boulder, CO, United States)
Gao, Ru-Shan (National Oceanic and Atmospheric Administration Boulder, CO, United States)
Woods, Sarah (Spec, Inc. Boulder, CO, United States)
Lawson, R. Paul (Spec, Inc. Boulder, CO, United States)
Pittman, Jasna (Harvard Univ. Blue Hill, MA, United States)
Date Acquired
October 30, 2017
Publication Date
February 10, 2017
Publication Information
Publication: Journal of Geophysical Research: Atmospheres
Publisher: AGU
Volume: 122
Issue: 11
ISSN: 2169-897X
e-ISSN: 2169-8996
Subject Category
Oceanography
Meteorology And Climatology
Numerical Analysis
Report/Patent Number
ARC-E-DAA-TN47591
Funding Number(s)
CONTRACT_GRANT: AFRC-Globa
CONTRACT_GRANT: AFRC DC-8
CONTRACT_GRANT: NNX12AD05A
CONTRACT_GRANT: AFRC-Globa
Distribution Limits
Public
Copyright
Portions of document may include copyright protected material.

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