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Ice Extent Timeseries not showing up

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bryamorihuela@...
Ice Extent Timeseries not showing up

Hi, 

This may be a dumb question but I could not fix it by myself.

I am using monthly output from cesm1.2, transforming the variables (MOC, PRECT, PSL, SNOWDP, TREFHT, TS and aice) to the right format and running the package.

It seems to run correctly without giving any error message and I got all the outputs correctly except for the Ice Extent Timeseries section which does not give any output.

Does someone have an idea on why this might be?

Cheers

Luis

P.S As mentioned, all the other plots work, including the Sea ICE (SH & NH) means and standard deviation

asphilli

Hi Luis,

The CVDP needs the area of each grid cell to calculate the ice extent timeseries. It does not calculate the area, but it does attempt to locate a file or array that contains this information in three ways:

1 - For CMIP data the package attempts to follow the same directory structure used by the ETH-Zurich archive, and to locate a file in fx/areacello/$run_name/r0i0p0/ directory that contains an areacello array. This solution is highly specific to the directory structure set up by ETH-Zurich and mirrored at NCAR.

2 - The CVDP looks for an array in the sic file itself named "AREA". The AREA array has to have a units attribute set to"m^2" or "km^2". 

3 - For CESM files, the package looks at the aice varable, and checks to see if there's a cell_measures attribute that is set to "area: tarea". If that attribute is set correctly, it then checks for the presence of a array named "tarea" in the file. If tarea is present, it uses that for the areas.

As you stated that you are analyzing CESM data, situation #3 should apply and you should check to make sure your aice array has a cell_measures attribute set as described above and that you have a tarea array present in the same file. 

For non-CESM data, if situation #1 does not apply, finding an existing array (or calculating the area for each grid point on your own) and putting that array in the model's sic file and naming it AREA is likely the best way to go.  If you happen to have a CMIP-equivalent areacello array for the model you are analyzing in an external file, adding this array to the model's sic file and renaming the array from areacello to AREA would work. 

Best,

Adam

 

 

bryamorihuela@...

Hi Adam,

That was very very useful! thanks a lot for your clear explanation.

I realised nco (command: cdo select,name=aice infile outfile) was not extracting that attribute (cell_measures) nor the tarea array. (If you happen to know anything about why is that, please let me know, if not, no worries I know this is not a cdo forum). I am also mentioning it, so that, if someone have the same issue in the future, by reading this, he/she can know what happened faster than me.

So, had to switch to NCO, which correctly passes the attribute and tarea.

Now is working fine.

Thanks again,

Luis

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