Help with interpreting Cable soil moisture output

Hi everyone,

I’m hoping to send soil moisture output from ESM1.5 to colleagues who are interested in analysing the soil moisture at 10cm. I haven’t found much information online and so was wondering if anyone had advice on interpreting the model output. I have the soil moisture variables mrsol_1, …, mr_sol_6 (moisture_content_of_soil_layer), though I’m not sure which one is suitable for ~10cm deep.

I was also wondering if anyone would be happy to clarify the “pseudo_level” coordinate in each of these variables?

Many thanks,

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Hi Spencer,

Quick replies - first you need to be sure whether your colleagues want soil moisture at 10cm down into the soil column, or soil moisture averaged over the upper 10cm layer of soil. These are different - the standard CMOR variable (mrsos) is the latter (and would be what I would guess they are looking to use).

Soil moisture in CABLE is calculated as layer averaged variable for each of 6 soil layers - these are the variables mrsol_1 etc. Layer depths are 0.022, 0.058, 0.154, 0.409, 1.085 and 2.872m. This means that the soil moisture at 10cm down is best represented by mrsol_3, whereas the mrsos is the weighted average of mrsol1_ through _3.

Finally ‘pseudo-level’ in this context refers to the use of tiled soils by CABLE - there is one soil column per land cover type within a grid cell. (In contrast the usual Met Office land model - MOSES in the case of ESM1.5 - uses only one soil column per grid cell). If your colleagues wish for grid-cell averaged soil moisture then you would have to take the appropriate area-weighted average across the different tiles.

There is a post-processing script which translates ESM/CABLE output into standard CMORised variables and deals with these problems (and others such as whether you’re interested in liquid/ice fractions and which may include unit conversions as well). It may be a good idea to reach out to the ACCESS-NRI to see whether that script could be applied to the runs you are looking at sharing.

More detail on CABLE in ESM1.5 is given in Kowalczyk et al. (2013) and the more recent ESM description papers led by Tilo Ziehn and Rachel Law.

cheers, Ian H


Hi Ian,

Thanks so much for clarifying how these variables are structured. Good point about the difference between mrsos and the moisture at 10cm.

I’ve had trouble using the post-processing scripts in the past, so will have a go at the calculations manually for now. Looking into the APP4 post-processing scripts here, it looks like it uses slightly different layer depths (e.g. 0.022, 0.08 , 0.234, 0.643, 1.728, and 4.6m in the cableSoilLevels() function). I was just hoping to double check whether these would be the right ones to use.

Many thanks,