[MITgcm-devel] woes with exf interpolating

[Matthew Mazloff]

Hello,

A problem has been found (thanks Fabien!) regarding a discontinuity in  
the wind fields around longitude 0/360.

My set-up is 1/6 of a degree and I use NCEP on a 1 degree grid and use  
exf interpolation.  Within ~1 degree east and west of longitude 0  
there is a discontinuity in the wind field -- it is small but quite  
significant in the x-derivative.  My guess is that the interpolation  
routine is not properly accounting for periodicity -- and instead  
perhaps incorporating zeros.

Some important stuff -- I am using NCEP winds -- not stress -- and I  
have switched to interp_method=2 instead of the hard-coded  
interp_method=1.  This is because with interp_method 1 (linear) there  
are discontinuities in the wind-stress curl everywhere.  With bicubic  
interp the curl is smooth -- with this exception around longitude 0

I was hoping someone with more expertise could shed light on this  
before I go digging in the code

Thanks!
-Matt