Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 9, 2459-2470, 2016
https://doi.org/10.5194/gmd-9-2459-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
25 Jul 2016
A consistent prescription of stratospheric aerosol for both radiation and chemistry in the Community Earth System Model (CESM1)
Ryan Reynolds Neely III1,2, Andrew J. Conley2, Francis Vitt2, and Jean-François Lamarque2 1National Centre for Atmospheric Science (NCAS) and the School of Earth and Environment (SEE), University of Leeds, Leeds, UK
2National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
Abstract. Here we describe an updated parameterization for prescribing stratospheric aerosol in the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM1). The need for a new parameterization is motivated by the poor response of the CESM1 (formerly referred to as the Community Climate System Model, version 4, CCSM4) simulations contributed to the Coupled Model Intercomparison Project 5 (CMIP5) to colossal volcanic perturbations to the stratospheric aerosol layer (such as the 1991 Pinatubo eruption or the 1883 Krakatau eruption) in comparison to observations. In particular, the scheme used in the CMIP5 simulations by CESM1 simulated a global mean surface temperature decrease that was inconsistent with the GISS Surface Temperature Analysis (GISTEMP), NOAA's National Climatic Data Center, and the Hadley Centre of the UK Met Office (HADCRUT4). The new parameterization takes advantage of recent improvements in historical stratospheric aerosol databases to allow for variations in both the mass loading and size of the prescribed aerosol. An ensemble of simulations utilizing the old and new schemes shows CESM1's improved response to the 1991 Pinatubo eruption. Most significantly, the new scheme more accurately simulates the temperature response of the stratosphere due to local aerosol heating. Results also indicate that the new scheme decreases the global mean temperature response to the 1991 Pinatubo eruption by half of the observed temperature change, and modelled climate variability precludes statements as to the significance of this change.

Citation: Neely III, R. R., Conley, A. J., Vitt, F., and Lamarque, J.-F.: A consistent prescription of stratospheric aerosol for both radiation and chemistry in the Community Earth System Model (CESM1), Geosci. Model Dev., 9, 2459-2470, https://doi.org/10.5194/gmd-9-2459-2016, 2016.
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Short summary
We describe an updated scheme for prescribing stratospheric aerosol in the Community Earth System Model (CESM1). The inadequate response of the CESM1 to large volcanic disturbances to the stratospheric aerosol layer (such as the 1991 Pinatubo eruption) in comparison to observations motivates the need for a new parameterization. Simulations utilizing the new scheme successfully reproduce the observed global mean and local stratospheric temperature response to the Pinatubo eruption.
We describe an updated scheme for prescribing stratospheric aerosol in the Community Earth...
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