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Re: [ferret_users] seeing some strange output in curvilinear grids


On 2/24/2014 3:25 AM, Ghansham Sangar wrote:

HI All

Thanks a lot for find precious time to try this dataset.
It is a geostationary satellite output.
And we expect the data to be like that. 
that means there is a bug when the curvilinear data gets plotted near the edges?
Can we submit this bug somehow?

You can always write here to the list, or to the contact_ferret email, mentioned here, http://ferret.pmel.noaa.gov/Ferret/support, if you think there is a bug.

The curvilinear plotting commands are not designed to work when the location data is missing.  I'll try to have a quick look at your dataset and see if I can see a way to make this work.

Meanwhile, is there a way to do some type of substituion in ferret.
Like I have a variable called count in the dataset and variable call bt_lut.
I want to generate another variable which is by subistuting bt_lut values into count variable.
That will get me the bt_image.

There is a syntax, IF-THEN masking,

Have a look at that and see if it's the kind of thing you want to do:

   yes? let out_var = if count gt 10 then bt_lut
Or, do you want a regridding operation to put data from one variable onto the grid of another variable?  If these don't answer your question, write back and show the grids of the variables, and explain more about what you want to do.

I hope I am able to convey.
One more issue:
Is "hPa" not a valid Pressure level unit string?

For some coordinate-axis units, Ferret is set up to do  internal conversions, particularly units of time, longitude, latitude. This means that a time axis in units of seconds and a time axis in units of days can be handled together, with data regridded from one time axis to the other, or plotted on the same plot.  A longitude axis with a range of -180:180 can be reconciled with another longitude axis in 0:360.

Ferret doesn't do anything of this sort with units of pressure. If hPa is listed as a unit on a coordinate axis or variable, Ferret will use that in the label, but it does not do any conversion between pressure and other units internally.  That is what is meant if you use a dataset with units of hPa and you see

yes? use my_pressures.nc
 *** NOTE: Units on axis "zaxis" are not recognized: hPa
 *** NOTE: They will not be convertible:


On Mon, Feb 24, 2014 at 2:09 PM, Hein Zelle <hein.zelle@xxxxxxxxxxxxx> wrote:
Russ Fiedler wrote:

> Actually this looks like a bug(?) with how the end points are being
> handled when the x/y coordinates contain missing values.

That's indeed the problem: curvilinear plots break when the coordinate
variables contain missing data.  The same thing can happen in some
mp_projection scripts when your (global) data includes a pole.

The solution in this case is to filter out any data points that have
missing data in the longitude or latitude variables.

Kind regards,


Dr. Hein Zelle
Senior consultant meteorology & oceanography

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