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Can CESM LME decade averages be used to force WRF?

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I am planning to investigate CESM1.1 LME output from the period from 1000 CE to 1300 CE. I remember a 2015 paper written by Cindy Bruyere et al., "Bias-Corrected CMIP5 CESM Data in WRF/MAPS Intermediate File Format" (Bias-Corrected CMIP5 CESM Data in WRF/MPAS Intermediate File Format | OpenSky) that describes how to force WRF with CESM output.

I am curious to know if CESM LME output can be first averaged over a number of decades and then be used to force WRF?

If you plan to run WRF for long-term climate simulation, then yes you can use the average soil data as input. Note that some spin-up time will be needed for the model to adjust between the upper air and soil condition.
Aloha Ming Chen!
I recently learned that I can use the nco operator ncra to average netCDF files. As a preliminary test, I plan to first average reanalysis data files by first converting them from grib format into netCDF format using cdo operators. It seems that one of the most obvious problems will be the spin up. Although the spin up of a six month long wrf simulation that I perform now only amounts to about 0.14% of the simulation time (6hrs/4320hrs), if I were to average 6 months of reanalysis data then the percentage of spin up would jump concomitantly to about 0.83% (6hrs/720hrs). If I were to average 50 years of reanalysis into one year, the spin up would comprise about 3.5%. A while ago, when I was planning to remove the spin up from my 6-month long simulations, I would include an extra day preceding the time period of interest, e.g., Oct31. I then planned to cut it out, but never figured out how to do it. Do you have any ideas about how to remove spin up from a run?
It's interesting that you mentioned using average soil data as input b/c I was thinking but what if the time period simulated included an extended drought? Thanks too for describing how the air and soil temperatures come into equilibrium during spin up; I never knew that.
There is consensus how long the spin-up time should be. Generally, soil condition is less important for short-term weather forecast because the weather is mainly determined by synoptic condition. For long-term climate simulation, however, the feedback and interaction between surface-atmosphere could accumulate and eventually affect the simulated climate. This is why we need a balanced (or to say realistic) soil-atmosphere condition.
Unfortunately we don't have a consensus how long the spin-up time should be. I remember reading a paper that run WRF for climate simulation. In that paper, the spin-up time is set to 9 months. Personally I think the spin-up time of 6-month to 1-year should be fine.
Hope this is helpful for you.