Changing albedo climatology in JULES

Hi,

I’m looking to run a UKESM1.0 AMIP version of the UM. I would like to prescribe my own forcing through changes to the albedo climatology within JULES, but I haven’t been able to find where I could specify this.

In the JULES radiation options menu there is an option to select “l_albedo_obs” (Scale albedo of land-surface tiles to agree with obs) but ticking it doesn’t bring up any additional fields. The help for this tickbox says this “Allows the UM to read in an ancillary file containing albedos (either SW(STASH 243) or VIS(STASH 244) and NIR(STASH 245)). […]” ).

Can you advise where I would be able to specify these files? In the Configure ancils and initialise dump fields menu I was able to find a stash_req item with 244,245, which lists the ancilfilename as $UM_ANCIL_GENLAND_DIR/$UM_ANCIL_GENLAND_FILE, which is a directory I wasn’t able to find. I also didn’t find a stash_req item #243 to specify SW albedo and was wondering if it would work to just add it under the same item as the one containing 244,245?

I’m working in u-de347.

Thanks in advance for any help!

Michaela

Hi Michaela:
Have you had any luck?
To find the path to: $UM_ANCIL_GENLAND_DIR (according to one of my colleagues), look "in an ancil versions file - possibly something like:

[env]
ANCILDIR=$ROSE_DATA/etc
ANCILVNFILE=$ROSE_DATA/etc/um_ancils_gl

in app/install_ancil/rose-app.conf/ or the equivalent in your suite."
Patrick McGuire

Hi Patrick,

Thanks for your help with this. Following your instructions, I found the desired directory listed as $ROSE_DATA/etc/ancil/qrclim.land.

Now that still left me wondering what directory $ROSE_DATA is referring to exactly, but I was then able to find a list of different qrclim.land files in /work/y07/shared/umshared/ancil/atmos (inspired by this post). A search in that folder returns several matches for “qrclim.land”, all of which are albedo files. I’m still not 100% clear on what the difference between all of them is and which one is being actually used in the run, as there are 15 different ones just for the n96e resolution, but they all seem to be in the same format so I think either will work for the creation of my own ancil file.

I will create my own SW albedo ancil file with forcings included and, unless anyone reading this thinks it’s an absolutely stupid idea and will not work, I am going to go ahead and change the existing stash request 244,245 to 243 so that I can input the SW albedo, instead of having to specify VIS and NIR separately (in Configure ancils and initialise dump fields).

Michaela

Hi Michaela
I’m glad you figured things out, and I think your plan (at least on the surface) sounds good.
One small issue: isn’t the range of wavelengths for SW (shortwave) the same as for VIS? I would guess that the NIR range of wavelengths is the same as would be any LW (longwave) file. But I guess you’d have to check such things.
Patrick

Hi Patrick,

I think this won’t be a problem; it seems that in JULES “SW flux” is defined as a combination of NIR and VIS (by default 50/50); this is at least my understanding of the “JULES radiation options” settings. This is also consistent with how MODIS defines SW for the purpose of albedo calculation. Hopefully the approach I outlined should therefore be fine (well, there might be other issues with it, but this is one fewer to worry about…)

Thanks again!
Michaela