[ecco-support] A question about ECCO-V4r2 Release2 data

[HONG ZHANG]

Hi Songna,
UVELMASS and VVELMASS in MITgcm are for native grid (here LLC90).
When plotted geographically, they should be rotated first.
Here is the reference
https://ecco.jpl.nasa.gov/products/latest/user-guide/
especially section 3.3.2.
In case you can't access, here are the copy of text and LLC grid map:
====
3.3.2 Native and Geographical Velocity ComponentsUsers are advised to be
aware of the directional convention used in the model especially when
analyzing the vector fields of the model. Figure 1b illustrates the
directional convention used in the LLC grid. Within each face (tile), the
x- and y-directions point left-to-right and bottom-to-top in the figure,
respectively. As such, in faces 4 and 5, the x- and y-directions point to
the south and to the east, respectively. In face 3, the x-direction points
to the Pacific Ocean away from the Atlantic, whereas y-direction points to
North America away from Asia. For user convenience, conventional eastward
and northward velocity components (EVEL and NVEL) are provided as
diagnostic output, in addition to that in the model’s native direction
(UVEL and VVEL). (See Table 1.)

====

cheers

Hong
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