Dear ferret users
I want to do 7 year lowpass filtering on a 60 year monthly data to remove the decadal variability. I had seen the lowpass filter function in ferret[LSL_LOWPASS(A, cutoff_period, filter_span)].
But I am confused with the filter span and cut-off period and how to use that. In literature, related to lowpass filtering the cut off frequency omega is defined as the range of frequency at which filtering performes.So in my case does it mean that cut off frequency is 7 year? or how will be the command line looks?
my_var = var_ano[l=1:600,x=40e:120e,y=20s:20n,k=1:20]
let var_filter = lsl_lowpass(my_var,7,600)
Thanks in advance.
Physical Oceanography Division
National Institute of Oceanography