[MITgcm-support] phivel / psivel

[Ryan Abernathey]

Hello,

I am trying to use the new diagnostics PhiVEL and PsiVEL to perform a
Helmholtz decomposition of my velocity fields.
48 |PhiVEL  |  1 |    45 |SMR P   MR|m^2/s           |Horizontal Velocity
Potential (m^2/s)
49 |PsiVEL  |  1 |    48 |SZ  P   MR|m.m^2/s         |Horizontal Velocity
Stream-Function

Phi looks great. However, in Psi, there are some discontinuities at tile
boundaries. This makes it impossible to take the derivatives to recover the
non-divergent component of the velocity field.

Figures and data files can be seen here:
http://nbviewer.ipython.org/gist/rabernat/677b0c95635928d3f05c

Has anyone experienced this problem? Any idea how to fix it? Possible bug?

Thanks,
Ryan


p.s. I found these comments in diag_calc_psivel.F. This sounds similar to
my problem. But I am not using OBCS, so I guess they don't apply.

C- Note: OB may introduce discontinuity in domain & tile stream-function
map;
C     within a tile: define a local "is-set" mask (=kPsi) and
C                    propagate stream-function value without assumption.
C     between tiles: present code is not "general", likely to work with
C                    simple OB setting and/or simple tile connection (no
exch2).
C     A truly general algorithm requires to change CUMULSUM_Z_TILE (adding 1
C     more input dPsi/tile) and to account for disabled tile-connection due
C     to OB when setting cumsum tile-mapping (W2_SET_MAP_CUMSUM).
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20150707/363d539a/attachment.htm>