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Long-Term Changes in Stratospheric Age Spectra in the 21st Century in the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM)In this study we investigate the long-term variations in the stratospheric age spectra using simulations of the 21st century with the Goddard Earth Observing System Chemistry- Climate Model (GEOSCCM). Our purposes are to characterize the long-term changes in the age spectra and identify processes that cause the decrease of the mean age in a warming climate. Changes in the age spectra in the 21st century simulations are characterized by decreases in the modal age, the mean age, the spectral width, and the tail decay timescale. Our analyses show that the decrease in the mean age is caused by two processes: the acceleration of the residual circulation that increases the young air masses in the stratosphere, and the weakening of the recirculation that leads to the decrease of tail of the age spectra and the decrease of the old air masses. The weakening of the stratospheric recirculation is also strongly correlated with the increase of the residual circulation. One important result of this study is that the decrease of the tail of the age spectra makes an important contribution to the decrease of the main age. Long-term changes in the stratospheric isentropic mixing are investigated. Mixing increases in the subtropical lower stratosphere, but its impact on the age spectra is outweighed by the increase of the residual circulation. The impacts of the long-term changes in the age spectra on long-lived chemical traces are also investigated. 37 2
Document ID
20120011786
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Li, Feng (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Waugh, Darryn W. (Johns Hopkins Univ. Baltimore, MD, United States)
Douglass, Anne R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Newman, Paul A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Strahan, Susan E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ma, Jun (Computational Physics, Inc. Springfield, VA, United States)
Nielsen, J. Eric (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Liang, Qing (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 26, 2013
Publication Date
January 1, 2012
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC.JA.01154.2012
Distribution Limits
Public
Copyright
Public Use Permitted.

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