Difference between bottom bathymetry variable, ht, and actual data in ACCESS-OM2-01

Technical
1

Hi all,

Apologies if this was obvious to everyone, but I just realised that the ht variable in ACCESS-OM2-01 is different to the actual bottom st_ocean cell where data is not NaN (for instance, temperature). See below for the difference between the two, which can be up to 40m in places in my region of the Ross Sea.

I know people define isobaths using the ht variable, but wouldn’t it be better to do so using the coarser bottom st_ocean cell where data is actually available for analysis? Masking would also yield slightly different results if we use bounds defined by ht vs. the actual data depth. Same applies for hu…

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2

Hi Taimoor,
MOM5 uses bottom partial cells, which allows the bathymetry to be flexible in between specified levels of st_ocean. So using ht should be accurate in most cases. If you have large variations of sea level (using the z* coordinate), the dynamic variable dzt will be a more accurate representation of total water column height.