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Impacts of the Convective Transport Algorithm on Atmospheric Composition and Ozone-Climate Feedbacks in GEOS-CCMConvective transport is one of the dominant factors in determining the composition of the troposphere. It is the main mechanism for lofting constituents from near-surface source regions to the middle and upper troposphere, where they can subsequently be advected over large distances. Gases reaching the upper troposphere can also be injected through the tropopause and play a subsequent role in the lower stratospheric ozone balance. Convection codes in climate models remain a great source of uncertainty for both the energy balance of the general circulation and the transport of constituents. This study uses the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM) to perform a controlled experiment that isolates the impact of convective transport of constituents from the direct changes on the atmospheric energy balance. Two multi-year simulations are conducted. In the first, the thermodynamic variable, moisture, and all trace gases are transported using the multi-plume Relaxed-Arakawa-Schubert (RAS) convective parameterization. In the second simulation, RAS impacts the thermodynamic energy and moisture in this standard manner, but all other constituents are transported differently. The accumulated convective mass fluxes (including entrainment and detrainment) computed at each time step of the GCM are used with a diffusive (bulk) algorithm for the vertical transport, which above all is less efficient at transporting constituents from the lower to the upper troposphere. Initial results show the expected differences in vertical structure of trace gases such as carbon monoxide, but also show differences in lower stratospheric ozone, in a region where it can potentially impact the climate state of the model. This work will investigate in more detail the impact of convective transport changes by comparing the two simulations over many years (1996-2010), focusing on comparisons with observed constituent distributions and similarities and differences of patterns of inter-annual variability caused by the convective transport algorithm. In particular, the impact on lower stratospheric composition will be isolated and the subsequent feedbacks of ozone on the climate forcing and tropopause structure will be assessed.
Document ID
20120015000
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Pawson, S. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nielsen, Jon E. (Science Systems and Applications, Inc. Greenbelt, MD, United States)
Oman, L. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Douglass, A. R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Duncan, B. N. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Zhu, Z. (Science Systems and Applications, Inc. Greenbelt, MD, United States)
Date Acquired
August 26, 2013
Publication Date
January 1, 2012
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC.ABS.6958.2012
Meeting Information
Meeting: American Geophysical Union
Location: San Francisco, CA
Country: United States
Start Date: December 3, 2012
End Date: December 7, 2012
Distribution Limits
Public
Copyright
Public Use Permitted.

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