[ferret_users] fitting zero centre line, at 0.5 mark and -0.5 mark horizontal lines

[afwande juliet <afwandej965@xxxxxxxxx>]

Dear users

I have made timeseries plot from standardized anomalies. Kindly help me on how to fit

1. trend line at zero line mark
2. trend line at 0.5 mark
   
3. trend line at -0.5 mark

The reason is I want  to define wet and dry years as those above or below -+0.5 mark

below is script and figure

Attachment: Int_annual_cycle_MAM_NEA.gif
Description: GIF image

Attachment: Inter_Annual_Cycle.jnl
Description: Binary data