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Aerosol optical depth in CESM LME

engeir

Eirik Enger
New Member
I have recently been looking at the paper Climate variability and change since 850 CE (Climate Variability and Change since 850 CE: An Ensemble Approach with the Community Earth System Model) and the corresponding data sets that go with it at www2.cesm.ucar.edu/models/experiments/LME.
What I would like to grab from the data set are aerosol optical depth values from the volcano forcing runs, but I wonder if what I found is the correct one, or if this is included in the data set at all.

I have been looking at the variable fields AODVIS and AODABS, specifically the file (found here)
b.e11.BLMTRC5CN.f19_g16.VOLC_GRA.001.cam.h0.AODVIS.085001-184912.nc
and the corresponding files for the five ensemble members. Are these files and variable fields are the correct ones to use for looking at aerosol optical depth in CESM LME? (The attached file showing "CL AOD" is CESM LME AODVIS ensemble median.)

The reason I am asking is because, when I look at the time series both AODVIS and AODABS have very small perturbations. The perturbations due to volcanoes are easily seen, but they are and order of magnitude smaller than what is used for example in the attached Figure5 (from Toohey and Sigl (2017), ESSD - Volcanic stratospheric sulfur injections and aerosol optical depth from 500 BCE to 1900 CE). Also attached is a plot of the ensemble median of the AODVIS that I obtained from the file mentioned above.

view_shifted.png
toohey-saod.png
 

peverley

Courtney Peverley
Moderator
Staff member
Hi,

I asked the scientists who authored the paper and got two answers:
The volcanic forcing file is located at:/glade/p/cesmdata/cseg/inputdata/atm/cam/volc/IVI2LoadingLatHeight501-2000_L18_c20100518.ncIVI2LoadingLatHeight501-2000_L18_c20100518.nc

You can read more about the forcing files on the LME project page: Instructions | Community Earth System Model
And:
I believe that volcanic aerosols are imposed offline and their effects are therefore not included in the AODVIS or AODABS fields, though they are evident in the radiation fields such as FSNTOAC.

Hope that helps,
Courtney
 
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