Updating to bedmachine landfrac

[PeterHjortLauritzen]

Rene Wijngaard has updated our MODIS land fraction dataset to GrIS and AIS high resolution bedmachine data over Greenland and Antartica. The difference between updated dataset and GMTED2010 is here:

[adamrher]

It seems the MODIS dataset considered the Antarctic ice shelves as ocean. This is technically correct (the ice shelves are floating on top of the ocean ... like sea ice). Rene purposefully considered ice shelves as land because for our purposes, it is better that we not zero out the ice shelves, since they are a 100 meters or so above ocean surface.

[JulioTBacmeister]

So what have we decided to do? If they are permanent year round features at 100m elevation it may be OK to treat them as land. I think the physically significant change we are after is reducing temperature biases over rapidly flowing coastal currents.

On Thu, May 19, 2022 at 3:30 PM Adam Herrington @.***> wrote:

It seems the MODIS dataset considered the Arctic ice shelves as ocean. This is technically correct (the ice shelves are floating on top of the ocean ... like sea ice). Rene purposefully considered ice shelves as land because for our purposes, it is better that we not zero out the ice shelves, since they are a 100 meters or so above ocean surface.

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[adamrher]

(corrected above post because I incorrectly referred to Arctic instead of Antarctic ice shelves). Those big Ross and Ronnie ice shelves are perennial. We should consider them land in our topo software, since we don't want to zero out elevations over ice shelves. So this new merged BM+MODIS landfrac product is a better dataset.

[PeterHjortLauritzen]

Here is plot of LANDFRAC on ~3km intermediate cubed-sphere grid

[JulioTBacmeister]

Sorry for a naive question - but why is there so much structure over land?

On Fri, May 20, 2022 at 9:39 AM Peter Hjort Lauritzen < @.***> wrote:

Here is plot of LANDFRAC on ~3km intermediate cubed-sphere grid

[image: Screen Shot 2022-05-20 at 9 39 16 AM] https://user-images.githubusercontent.com/8782989/169563332-4c66ce51-4061-4a49-8bde-afa5c9b9d125.png

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[PeterHjortLauritzen]

Here is screenshot of raw ~1km data:

Currently we are binning from ~1km lat-lon grid to ~3km intermediate cubed-sphere grid. I think the cubed-sphere data looks correct.

For comparison here is surface height of ~1km raw data: