It does not work because hdivg(u,v) or du/dx + dv/dy require varying x and y. But in vertical cross section Grads is set for single x or y as you showed.

You may try to calculate the divergence at each height level by using loop in grads script and write the result down to a binary file with 'gxout fwrite' command. And then create a new control file for cross-section plotting.

Hi Muhammad.

I think, if you write commond on Grads is better than. And, you attention script, line 4, you don't put ' in end line.

I hope, you can solve, but if you can't, i put my email and you could send me emaill, for meeting in the platform skype. Maybe i can help you.

My emaill: [email protected].

Thanks

I used fwrite function (after heavy trial and error effort) to create a binary file with divergence already calculated (hdivg) from the original netCDF file (as per Muhammad Rais Abdillah suggestion). However, the calculated divergence data, 'hdivg(u,v)', in a binary is suspect, because the map or vertical cross-section images are rather funny/suspicious (see attached image). Funny enough, to countercheck my script, I used the same script to write correct u-wind data in an output binary file; this means that my script is correct!

I ask myself, is there any issues with hdivg function? Does the function work differently in different data formats?

Also, thank you Arman Jahedi for your offer; I have discovered that I can straight get divergence field from ERA5 dataset; I don't need to calculate. From this data I can just display the vertical cross-sections.

Hi Elisa.

I think, you shouldn't write commnd in the between ' ' , because you know in the program grads, this case associate with error. But if you write commnd in the script, this is correct, but in the program grads with state you're wite, it's mistake. And that's one important, it's time in the netcdf file, in this commnd you writed 'set t 3015, for other commnd you put ' in the end, but you don't put ' for set t 3015 in the end commond. Let me write for you commnd in the Grads, like this:

sdfopen u.nc

sdfopen v.nc

set lon 15 55

set lat -9

set lev 925 200

set t 3015

set gxout shaded

d hdivg(u,v.2)

Thanks