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Published December 16, 2017 | Supplemental Material + Published
Journal Article Open

Radiative and Chemical Response to Interactive Stratospheric Sulfate Aerosols in Fully Coupled CESM1(WACCM)

Abstract

We present new insights into the evolution and interactions of stratospheric aerosol using an updated version of the Whole Atmosphere Community Climate Model (WACCM). Improved horizontal resolution, dynamics, and chemistry now produce an internally generated quasi-biennial oscillation and significant improvements to stratospheric temperatures and ozone compared to observations. We present a validation of WACCM column ozone and climate calculations against observations. The prognostic treatment of stratospheric sulfate aerosols accurately represents the evolution of stratospheric aerosol optical depth and perturbations to solar and longwave radiation following the June 1991 eruption of Mount Pinatubo. We confirm the inclusion of interactive OH chemistry as an important factor in the formation and initial distribution of aerosol following large inputs of sulfur dioxide (SO_2) to the stratosphere. We calculate that depletion of OH levels within the dense SO_2 cloud in the first weeks following the Pinatubo eruption significantly prolonged the average initial e-folding decay time for SO_2 oxidation to 47 days. Previous observational and model studies showing a 30 day decay time have not accounted for the large (30–55%) losses of SO_2 on ash and ice within 7–9 days posteruption and have not correctly accounted for OH depletion. We examine the variability of aerosol evolution in free-running climate simulations due to meteorology, with comparison to simulations nudged with specified dynamics. We assess calculated impacts of volcanic aerosols on ozone loss with comparisons to observations. The completeness of the chemistry, dynamics, and aerosol microphysics in WACCM qualify it for studies of stratospheric sulfate aerosol geoengineering.

Additional Information

© 2017. American Geophysical Union. Received 20 APR 2017. Accepted 23 OCT 2017. Accepted article online 6 NOV 2017. Published online 7 DEC 2017. Special Section: Simulations of Stratospheric Sulfate Aerosol Geoengineering with the Whole Atmosphere Community Climate Model (WACCM) This article is a companion to MacMartin et al. (2017), https://doi.org/10.1002/2017JD026868, Richter et al. (2017), https://doi.org/10.1002/2017JD026912, Kravitz et al. (2017), https://doi.org/10.1002/2017JD026874, and Tilmes et al. (2017), https://doi.org/10.1002/2017JD026888. We thank Vladislav Gerasimov and Vladimir V. Zuev for providing lidar data from Tomsk. Mauna Loa lidar data were provided by NOAA ESRL Global Monitoring Division, Boulder, Colorado, USA (http://esrl.noaa.gov/gmd/). We thank Richard Allan for providing the merged ERBS data. We thank Diane Ivy for providing the polar cap average SBUV data. We thank Anne Smith, Dan Marsh, and three anonymous reviewers for providing many helpful comments on this manuscript. This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions, and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government. We acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation. The CESM project is supported by the National Science Foundation (NSF) and the Office of Science (BER) of the U. S. Department of Energy (DOE). The National Center for Atmospheric Research is funded by the NSF. The Pacific Northwest National Laboratory is operated for the U.S. DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. The output of all model simulations discussed in this study are available at the NCAR Earth System Grid at doi:10.5065/D6PC313T. Data presented in this work, including the source code used for these simulations, may be obtained from M. J. M. (email: mmills@ucar.edu).

Attached Files

Published - Mills_et_al-2017-Journal_of_Geophysical_Research__Atmospheres.pdf

Supplemental Material - jgrd54224-sup-0001-2017JD027006-SI.doc

Supplemental Material - jgrd54224-sup-0002-2017JD027006-ts01.xlsx

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