NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Insights on TTL Dehydration Mechanisms from Microphysical Modelling of Aircraft ObservationsThe Tropical Tropopause Layer (TTL), a transition layer between the upper troposphere and lower stratosphere in the tropics, serves as the entryway of various trace gases into the stratosphere. Of particular interest is the transport of water vapor through the TTL, as WV is an important greenhouse gas and also plays a significant role in stratospheric chemistry by affecting polar stratospheric cloud formation and the ozone budget. While the dominant control of stratospheric water vapor by tropical cold point temperatures via the "freeze-drying" process is generally well understood, the details of the TTL dehydration mechanisms, including the relative roles of deep convection, atmospheric waves and cloud microphysical processes, remain an active area of research. The dynamical and microphysical processes that influence TTL water vapor concentrations are investigated in simulations of cloud formation and dehydration along air parcel trajectories. We first confirm the validity of our Lagrangian models in a case study involving measurements from the Airborne Tropical TRopopause EXperiment (ATTREX) flights over the central and eastern tropical Pacific in Oct-Nov 2011 and Jan-Feb 2013. ERA-Interim winds and seasonal mean heating rates from Yang et al. (2010) are used to advance parcels back in time from the flight tracks, and time-varying vertical profiles of water vapor along the diabatic trajectories are calculated in a one-dimensional cloud model as in Jensen and Pfister (2004) but with more reliable temperature field, wave and convection schemes. The simulated water vapor profiles demonstrate a significant improvement over estimates based on the Lagrangian Dry Point, agreeing well with aircraft observations when the effects of cloud microphysics, subgrid-scale gravity waves and convection are included. Following this approach, we examine the dynamical and microphysical control of TTL water vapor in the 30ºS-30ºN latitudinal belt and elucidate the dominant processes in the winter and summer seasons. Implications of the TTL dehydration processes for the regulation of global stratospheric humidity will be discussed.
Document ID
20160005031
Acquisition Source
Ames Research Center
Document Type
Abstract
Authors
Ueyama, R.
(Oak Ridge Associated Universities Moffett Field, CA, United States)
Pfister, L.
(NASA Ames Research Center Moffett Field, CA, United States)
Jensen, E.
(Concentric Real Time, LLC Ellicott City, MD, United States)
Date Acquired
April 14, 2016
Publication Date
January 12, 2014
Subject Category
Geophysics
Meteorology And Climatology
Report/Patent Number
ARC-E-DAA-TN12138
Meeting Information
Meeting: SPARC General Assembly 2014
Location: Queenstown
Country: New Zealand
Start Date: January 12, 2014
End Date: January 17, 2014
Sponsors: Environmental Research Inst. of Michigan
Funding Number(s)
CONTRACT_GRANT: NNH06CC03B
CONTRACT_GRANT: NNG10CR08C
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
stratosphere
tropical regions
dehydration
No Preview Available