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Dust information in CMIP5 CESM1(CAM5)

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psagar@...
Dust information in CMIP5 CESM1(CAM5)

I am looking at the CMIP5 results of CESM1 (CAM5). I know that the compsets used in historical and RCP experiments are B_1850-2000_CAM5_CN and B_RCP4.5_CAM5_CN respectively which are fully coupled simulations. In the forcing information page http://www.cesm.ucar.edu/CMIP5/forcing_information/, it is written that dust (Ds) and Mineral Dust (MD) forcing is 'varying'. What is the difference between Ds and MD? Could you please tell what does this 'varying' mean? Is the mineral dust prescribed or is it simulated by the CAM5 dust model or CLM dust model?


Thank you,


-Sagar

mahowald@...

Hi!

I did not do the CAM5 runs, but I think what happened was that the prognostic dust (as described in Mahowald et al., 2006, Liu et al., 2013) was turned on, and thus dust emission was calculated prognostically within the model, allowed to vary, but there was no attempt to FORCE the dust emissions to match any particular trend (e.g. the historical trends from Mahowald et al., 2010) or account for changes in land use (e.g. as done in Ward et al., 2014).  Thus, the time trends were from soil moisture or vegetation trends, wind changes or chagnes in atmospheric transport, and which tend to be quite small compared to what we see in the obs (as you can see in those papers).

It is possible that the emissions were prescribed from the CAM4 runs (Lamarque et al., 2010), but my memory was that they were prognostically calculated.  I do not think at this time that the ability to have prescribed aerosols was in the CAM5.  If you need this verified, you should contact Steve Ghan or Phil Rasch, although Rich Neale or Cecile Hannay might know also when the prognostic aerosols were enabled for CAM5.


I do not know why they put Ds and MD in the table: there is only one of these.  Maybe because also deposition impacts the land snow albedo, and thus someone else entereed it there, on accident?

 

CAM5 dust uses calculations for emissions in the CLM dust module, to some extent, although modified by a soil erodibility map and sizes when it comes into the CAM5.

 

Please note that the optics and the soil erodibility map were later improved for cam5: the ones in the cmip5 archive aren't very good: Albani et al., 2014, available from my web page.I would not reocmmend using the CMIP5 dust output from any of either CAM4 or CAM5 for science purposes, except to interpret CMIP5 results, because of the problems in the dust.

If you have more specific quesitons, feel free to email me directly.

 

Thanks

Natalie

xiongfelin@...

Hi!

Thanks for your answer. And may I ask you a question?

When I use simulating surface air temperature  from CCSM4 historicalMisc experiment in CMIP5, I also hope to use  sulfate concentration from the sulfate direct effect experiment (r1i1p15). Just like this information  http://www.cesm.ucar.edu/CMIP5/forcing_information/

I can not find or download this simulation data form "ESGF-Node at DKRZ".Would you tell me where can I download or search  the sulfate concentration? 

 

Thank you  so much 

Felin

strandwg

All CMIP5 data from NCAR is available from the NCAR gateway at

https://www.earthsystemgrid.org

For the CMIP5 run you mention, start here:

 

https://www.earthsystemgrid.org/search.html?Project=CMIP5&Experiment=historicalMisc&Ensemble=r1i1p15

mahowald@...

Hi!

I don't thnk there is really a difference between MD and D, unless it is whether they are prognostic or prescribed.  Whoever wrote this document would have to tell you if there was a difference, but int he model there is only mineral dust, which we also refer to as dust.

I assume varying (which I can't see where you finding this) indicates that the forcing is from prognostic dust. Prognostic dust is calculated within the model based on vegetation, soil moisture, surface winds using the dust module.  prescribed is read in from a tape.

Please recognize that the default version of CAM4 and CAM5 included in CESM1 and all the way untill CESM2 had errors in it (the optics used for dust in the default version were outdated): see Albani et al., 2014 to see that these errors are important for the climate response and radiative forcing.

Thanks

Natalie Mahowald

strandwg

What the "varying" means is that the dust is changing during the course of the run, not fixed.

 

xiongfelin@...

Hi

Thanks for your answer, I want to know is there output data for changing dust after the course of the run. If there is that, where can I download?

 

Felin

mahowald@...

Hi!

I'm not sure what you mean.  Do you mean you want to look at what the dust is doing during the run and have output?  Or you want to drive the dust with the prescribed aerosol?  There are many dust variables that you can trigger to get output, and there is a new flag: history_dust = .true, in CESM2 which will trigger a bunch of output variables so you can evaluate the dust.  If it is the second, just use the prescribed aerosol flag instead of prognostic: I think that works, but I do not usually use that compset.

Thanks

Natalie

xiongfelin@...

Hi!

I am understand what your mean. I don't konw how to run the model and only want to analysis the CMIP5 output data. According to your opinion,  I think there isn't aerosol output data in CCSM4 of CMIP5. But no matter what, thank you

Felin

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