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Re: [ferret_users] making a continuous timesaxis with JJAS values

Thank you for a quick reply.

On Mon, Jul 23, 2018 at 10:53 PM, Ansley C. Manke <ansley.b.manke@xxxxxxxx> wrote:

Hi Chinnu,

If you have defined the monthly axis so that it really lines up with your JJAS time axis, then the values won't be changed with a linear interpolation.  "Monthly" time is a bit ambiguous, so if the time coordinates aren't exactly the same on the axis you define, then Ferret will do some interpolating between the axes.

Look at the details for a few months of your axes:

   yes? ! the axis of your original data
   yes? show axis/t=1-jun-1948:30-sep-1949 `var,return=taxis`

   yes? ! the axis you are defining
   yes? show axis/t=1-jun-1948:30-sep-1949  tax_mon

Do the coordinates have the same dates and times for the months that are present on the original data axis?  Are they both regularly spaced?  The two axes do NOT need to have the same units. Ferret converts between different time units so if your original data has units of days or hours, that's fine. But if the coordinates don't agree, then the data will be interpolated. 

You could try to define your monthly time axis so that the coordinates for JJAS match on both axes, or look at using a different regridding transformation.


On 7/23/2018 5:17 AM, chinnu sachi wrote:
Dear Ferret users,
                           I have time series which had only four month( ie JJAS ) values.

 1948  jun    1.370
 1948  jul   1.636
 1948  aug  1.542
 1948  sep   1.832
 1949  jun  0.523
 1949  jul  0.220
 1949  aug  0.532
 1949  sep  1.313
 1950  jun  0.275
 1950  jul  1.068
 1950  aug  1.100
 1950  sep  1.347
etc till
 2015  jun  -1.662
 2015  jul  -3.908
 2015  aug  -3.032
 2015  sep  -2.286

 I would like to make above time axis into a continuous one from january to december for the entire data period without having any change in the JJAS values. I tried to define a grid with

DEFINE AXIS/t=15-jun-1948:15-sep-2015:1/UNITS=months tax_mon
LET var_new = var[Gt=tax_mon@lin]
save/file=out.nc/clobber var_new

I am getting continuous time axis from january to december for 1948 to 2015, but the values of JJAS of each year has been changed.

Thanks in advance.

Chinnu Sachidanandan

Chinnu Sachidanandan

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