I have been trying and failing to reproduce a domain from the RACMO group over Antarctica as shown here:
I would normally do this by setting the domain centre, but as you can see the desired domain is slightly tilted, which I can’t achieve just by setting the domain centre.
I managed to create it in Lampos on pumatest (by the way, is lampos available anywhere on pumanew? How can I run it if so?) using the coordinates specified below:
ny, nx = 688, 560
Centre of domain lon/lat: 20.000 -85.000
Pole lon/lat: 20, -175
BLC lon/lat: -37.400 -29.500
grid spacing = 0.1 degree
You can see the results here:
There are a couple of differences between RACMO and the UM: 1) RACMO specifies longitudes as -180 to +180 instead of the 0-360 in the UM. 2) RACMO’s pole latitude for this domain is -175, which is obviously unphysical and is their way of forcing the domain centre to be at -85. Given that the UM rotation works by rotating lats by 90 degrees relative to the domain centre and leaves lons alone, I would’ve thought that in UM notation this should be written as 5, 20. However, as you can see in the above image, I could only force the domain to be in the southern hemisphere by setting the pole lat to -5.
There are also some differences between the coordinates in the image and the ones I’m using because I was originally going for 0.11 degree, and am now using 0.1, plus lampos only accepts whole numbers.
After I adapt the inputs given these two things and put them into the suite to generate ancils, the domain is shifted very slightly to the right, such that it includes Macquarie island, which is outside the right-most boundary in the image and doesn’t include enough of the South American continent. The rounding to whole numbers between lampos/the suite also doesn’t really explain the differences I’m seeing.
It’s driving me up the wall because I can’t figure out why this might be happening! Has the rotation routine changed since vn4.5? I’m also struggling to get my head around how the rotation works when you’re specifying the BLC instead of domain centre. Do I need to adjust my BLC somehow?
If anyone can help me out of my misery I will be most grateful.