[Cesm2control] Coupled SC-WACCM vs CAM runs: 1850 and HIST

Michael Mills mmills at ucar.edu
Mon Feb 19 15:39:10 MST 2018

I have been running coupled SC-WACCM simulations for 1850 and for 1976-2014. Although progress has been hindered by machine issues this weekend, I have some early results in the linked slides. These runs were set up to be consistent with Cecile’s 269 runs, and are compared to them.

These runs were motivated by concerns about differences between WACCM and CAM that might affect surface climate. Specifically, we have noticed significant cooling in the winter polar stratosphere in CAM compared to WACCM. 

There were also concerns about the magnitude of cooling from volcanic eruptions in CAM, which are driven by output from a historical CAM-chem simulation with prognostic volcanoes. In the SC-WACCM historical run, I have replaced the CAM-chem forcings with those from a WACCM historical simulation. Unfortunately, that WACCM run was initialized in 1975 without volcanic input from the 1974 eruption of Fuego, so there is some missing stratospheric aerosol in the first few years of the SC-WACCM historical simulation.

Some observations follow, along with run information.

RESTOM is up by 0.25-0.3 W m-2 in SC-WACCM
case: /glade/p/work/mmills/case/b.e20.BWsc1850.f09_g17.269
run: /glade2/scratch2/mmills/b.e20.BWsc1850.f09_g17.269/run
archive: /glade2/scratch2/mmills/archive/b.e20.BWsc1850.f09_g17.269/

The WACCM volcanoes are shorter-lived than the CAM-chem volcanoes. This has been seen in multiple free-running WACCM simulations. Therefore the forcing from volcanoes in CAM may be reduced when the switch is made to using WACCM volcanoes following the full (1850-2014) coupled historical WACCM simulation.
While the cooling in response to Pinatubo in the CAM run appears to be strong, little cooling is seen following the 1974 and 1982 eruptions. Both models also exhibit inter-annual cooling that appears unrelated to large eruptions. 
case: /glade/p/work/mmills/case/b.e20.BWscHIST.f09_g17.269
run: /glade2/scratch2/mmills/b.e20.BWscHIST.f09_g17.269/run
archive: /glade2/scratch2/mmills/archive/b.e20.BWscHIST.f09_g17.269/

Cheyenne has just been returned to service, and these runs are now continuing.

https://www.dropbox.com/s/ane6icyfv8v3z8q/2018.02.18%20WACCM%20Coupled%20SC.pptx?dl=0 <https://www.dropbox.com/s/ane6icyfv8v3z8q/2018.02.18%20WACCM%20Coupled%20SC.pptx?dl=0>

Mike Mills
CESM WACCM Community Liaison
Atmospheric Chemistry Observations & Modeling Laboratory
National Center for Atmospheric Research
P.O. Box 3000, Boulder, Colorado 80307-3000
phone: 303.497.1425       fax: 303.497.1400        email: mmills at ucar.edu <mailto:mmills at ucar.edu>
https://acomstaff.acom.ucar.edu/mmills/ <https://acomstaff.acom.ucar.edu/mmills/> 
WACCM forum: https://bb.cgd.ucar.edu/forums/whole-atmosphere-modeling-waccm <https://bb.cgd.ucar.edu/forums/whole-atmosphere-modeling-waccm>
Packages mail to: 3090 Center Green Dr. Boulder, CO 80301

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