Award Abstract # 1261948
Understanding Long-term Variations in Stratospheric Water Vapor

NSF Org: AGS
Division of Atmospheric and Geospace Sciences
Recipient: TEXAS A & M UNIVERSITY
Initial Amendment Date: April 4, 2013
Latest Amendment Date: April 4, 2013
Award Number: 1261948
Award Instrument: Standard Grant
Program Manager: Eric DeWeaver
edeweave@nsf.gov
 (703)292-8527
AGS
 Division of Atmospheric and Geospace Sciences
GEO
 Directorate for Geosciences
Start Date: April 1, 2013
End Date: March 31, 2017 (Estimated)
Total Intended Award Amount: $259,112.00
Total Awarded Amount to Date: $259,112.00
Funds Obligated to Date: FY 2013 = $259,112.00
History of Investigator:
  • Andrew Dessler (Principal Investigator)
    adessler@tamu.edu
Recipient Sponsored Research Office: Texas A&M University
400 HARVEY MITCHELL PKY S STE 300
COLLEGE STATION
TX  US  77845-4375
(979)862-6777
Sponsor Congressional District: 10
Primary Place of Performance: Texas A&M University
TAMU 3150
College Station
TX  US  77843-3150
Primary Place of Performance
Congressional District:
10
Unique Entity Identifier (UEI): JF6XLNB4CDJ5
Parent UEI:
NSF Program(s): Climate & Large-Scale Dynamics
Primary Program Source: 01001314DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 0000, OTHR
Program Element Code(s): 574000
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

This project seeks to understand changes in tropical stratospheric water vapor seen in observations and in model simulations of future climate change. Simulations of future climate consistently show an increasing trend in tropical stratospheric water vapor due to greenhouse gas increases, but satellite data since the 1980s show interannual and decadal variability but little trend. In addition, comparison of monthly stratospheric water vapor and 100hPa heating rate are negatively correlated in observational data, but positively correlated in future climate simulations. Negative correlations are expected if changes in water vapor and heating rates are linked to variations in the Brewer-Dobson circulation, as a stronger BD circulation is associated with stronger tropical heating (i.e. stronger diabatic upwelling) and colder tropical stratospheric temperatures. But future climate simulations show increases in both water vapor and the strength of the BD circulation. Moreover, increases in surface temperature are expected to produce increases in stratospheric water vapor, but surface temperatures rose over the observed record while tropical stratospheric water vapor did not. This project uses a suite of models including a domain-filling trajectory model, the Whole Atmosphere Community Climate Model (WACCM), and a one-dimensional radiative transfer model, to understand the underlying processes responsible for the changes in observed and simulated water vapor changes.

The work has broader impacts due to the climatic effects of stratospheric water vapor, and the relationship between stratospheric ozone and water vapor. In addition, the PI will conduct outreach to general audiences through new-media outlets, thereby working to increase public understanding of the phenomena addressed in this research. The project also supports and trains a graduate student, thereby providing for the development of the scientific workforce in this research area.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Dessler, A. E.H. YeT. WangM. R. SchoeberlL. D. OmanA. R. DouglassA. H. ButlerK. H. RosenlofS. M. DavisR. W. Portmann "Transport of ice into the stratosphere and the humidification of the stratosphere over the 21st century" Geophysical Research Letters , v.43 , 2016 10.1002/2016GL067991
Dessler, A.E., M.R. Schoeberl, T. Wang, S.M. Davis, and K.H. Rosenlof "Stratospheric water vapor feedback" Proc. Natl. Acad. Sci. , v.110 , 2013 , p.18,087 10.1073/pnas.1310344110
Dessler, A.E., M.R. Schoeberl, T. Wang, S.M. Davis, K.H. Rosenlof, and J.-P. Vernier "Variations of stratospheric water vapor over the past three decades" J. Geophys. Res. , v.119 , 2014 10.1002/2014JD021712
Schoeberl, M., A. Dessler, H. Ye, T. Wang, M. Avery, E. Jensen "The impact of gravity waves and cloud nucleation threshold on stratospheric water and tropical tropospheric cloud fraction" Earth and Space Sciences , v.3 , 2016 , p.295 10.1002/2016EA000180
Wang, T.Dessler, A. E.Schoeberl, M. R.Randel, W. J.Kim, J. E. "The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor" Atmospheric Chemistry and Physics , v.15 , 2015 , p.3517 10.5194/acp-15-3517-2015
Wang, T., W.J. Randel, A.E. Dessler, M.R. Schoeberl, and D.E. Kinnison "Trajectory model simulations of ozone (O3) and carbon monoxide (CO) in the lower stratosphere" Atmos. Chem. Phys. , v.14 , 2014 , p.7135 10.5194/acp-14-7135-2014

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

This proposal is focused on analyzing and understanding the mechanisms that control stratospheric water vapor and testing whether climate models appropriately simulate them.  Much of our work focused on demonstrating the existence and estimating the strenght of a stratospheric water vapor feedback, where a warming climate increases stratospheric water vapor, which in turn further warms the surface.  While it had been previously speculated, ours was the first analysis to demonstrate its existence in observations (Dessler et al., PNAS, 2013).  We leveraged this work to explain the variability of water vapor over the last few decades (Dessler et al., JGR, 2014).  That paper showed that there was little long-term trend in stratospheric water vapor; previous suggestions that a trend existed has mistakenly confused short term variability for long-term behavior.  That paper also yielded an estimate of the impact of Mt. Pinatubo on the humidity of the stratosphere.  Finally, we studied the cause of long-term trends in two climate models.  The conventional wisdom is that these trends are caused by a warming tropopause. We found that, while a warming tropopause is indeed a primary contributor, much of the trend is due to an increase in convectively lofted ice evaporating in the lower stratosphere (Dessler et al., GRL, 2016).

In addition to these major results, we also published several papers exploring particular mechanisms or phenomena of interest.  This includes the impact of small-scale, unresolved temperature fluctuations (Wang et al., 2015), transport of O3 and CO in the TTL (Wang et al, 2014), the details of convective ice injection (Yu et al., in prep), and the details of how the the seasonal cycle is generated (Wang et al., in prep). These studies were written by graduate students supported by this grant, contributing to the education of future members of the atmospheric sciences community.

 


Last Modified: 04/07/2017
Modified by: Andrew E Dessler

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