[gradsusr] How to make zero line visble in GrADS line plot

[Mubashar Ahmad]

Dear GrADS users,

I have plotted an area averaged temperature anomaly (let say) with
time  in GrADS and wanted to make zero line visible on y axis so that
my graph clearly tell how many values of my plotted line are above and
below zero line on the y axis. How to do that?

Thanks,

Mubashar