Re: [ferret_users] How to flip a variable? U is read at reverse

Hi Karen,

There is the 'positive' netcdf attribute for the Z-axis, which can be 'up' or 'down'. In your case,

depth_u:positive = "up";

If not specified, Ferret assumes 'down' for an axis whose name starts with 'depth', and assumes 'up' for names starting with 'elev', 'height', 'level', 'layer'. So you could also try a different name that is more typical for positive values going up.

Kind regards,

Karl

On Wed, Jan 31, 2018 at 1:32 PM, karen guihou <karen.guihou@xxxxxxxxx> wrote:

Hi all

I am struggling with some ROMS files that I try to read. The surface is at level 40, and the bottom at level 1.
When I import the netcdf, Ferret automatically flips (I do not understand how/why) the U,V,T,S variables so that k=1 is now at the surface and k=40 is at the bottom. However, it does not flip the depth variable. My depths levels are negative values.

If I do u*depth, I end up multiplying the bottom by the surface. If I plot a vertical section of U, the max velocities are at the bottom...

Any idea of option to give, or some missing attribute in the netcdf? I created the nc from a mat file.
Thank you in advance!

netcdf U_climato_CMM {
dimensions:
z = 40 ;
lat = 384 ;
<

Karl M. Smith, Ph.D.
JISAO Univ. Wash. and PMEL NOAA
"The contents of this message are mine personally and do
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