[Thread Prev][Thread Next][Index]

Re: [ferret_users] vertical coordinates

Hi Patrick,
Also, once you have opened your file in Ferret, you can just use the command 


to have Ferret treat it as a depth axis.  Note how there is now a minus sign in the #pts column on the SHOW AXIS listing.
yes? use multipleaxis.nc
yes? sh axis/all   
 name       axis              # pts   start                end

 SIGMA     Z                   11 i   0.019148             0.98942
 ALT       Z (Km)              11 i   0.12948              37.295

yes? set axis/depth sigma
yes? sh axis/all
 name       axis              # pts   start                end

 sigma     Z                   11 i-  0.019148             0.98942
 ALT       Z (Km)              11 i   0.12948              37.295

and when you plot a variable whose Z axis is sigma, its upper axis will have the axis in the correct direction.


Ansley Manke wrote:
Hi Patrick
Yes, you can have vertical axes with different senses, positive upwards or or downwards.

If you are creating the netcdf file, then adding this attribute to the axis will ensure that it is treated as a depth axis.

               sigma:positive = "down" ;

Or if defining an axis in Ferret, just add the qualifier /DEPTH to the definition of the axis when it is to be positive in the downward direction.


Brockmann Patrick wrote:
Hi all,

How to store two vertical coordinates in different order in a netCDF file ?

I have a 3D variable XYZ where Z is a sigma vertical coordinate
(from 1 at ground to 0 at the top of the atmosphere).
The netcdf variable is stored with k=1 ground, k=11 top of the atm

Now, if I define sigma as
sigma = 0.989417, 0.9596861, 0.9065547, 0.8214576, 0.7043947, 0.5639313,
   0.4149028, 0.2744395, 0.1573766, 0.07227948, 0.01914804 ;
So with a decreasing order
when I open the file with ferret, the axis is reordered and variable is then available with
an increase axis.
Thus I get
yes? shade var[k=1] representing top of the atmosphere. It should be ground.

The problem could be a simple convention to accept but it is more complicated to explain
if you have 2 vertical axis such as an altitude (with an increasing order) and a sigma (with a descreasing order).
In first case k=1 will represent ground, k=11 in the second case.
k=1 should reprensent the ground in both case.

So is there a way to store in a netcdf file, one vertical axis in a descreasing order and one in
an increasing order ?


[Thread Prev][Thread Next][Index]

Contact Us
Dept of Commerce / NOAA / OAR / PMEL / TMAP

Privacy Policy | Disclaimer | Accessibility Statement