If A is your 20-year time series and ACL is your 12-month climatology:
First, put the climatology on a modulo time axis:
let ACLMOD = ACL[gt=month_reg@mod]
Extend it to the time axis of A:
let ACLRG = ACLMOD[gt=A]
let ADM = A - ACLRG ! anomalies
Sent from my phone .... Please excuse my brevity .... and my typing.
> On Jul 9, 2017, at 4:06 PM, Paul Goddard <pgoddard@xxxxxxxxxxxxxxxxx> wrote:
>
> Hi all,
>
> It is likely that an answer is already on the ferret users archive, if so, just refer me to that page, but I could not find what I was looking for.
>
> I have a monthly climatology, so 12 time steps. I would like to subtract the climatology off a 20 year monthly data set (of 240 time steps) to end with an anomaly with 240 time steps. How can I regrid the 12 climatologies to a 240 time step axis with the 12 months of the climatology just repeated 20 times.
>
> Thanks in advance,
> Paul