Re: [ferret_users] interpolate along time axis

Making me think about the descriptor file helped.

After a bit a trial and error I found that my descriptor file was poorly defined. In the &BACKGROUND RECORD I had "D_TIME_UNIT = 432000", corresponding to 5 days in seconds, and each files' S_START and S_END numbered in sequence (0,1,2,3,4...). When I switched this to D_TIME_UNIT = 86400 (1 day in secs) and files numbered in units of 5 (0, 5, 10, 15...), it worked.

This was quite confusing given the descriptor file seemed to work (i.e. displayed data at correct times). It's only when I tried to transform the data that I ran into a problem.

Michael Hughes

PhD Candidate

Environmental Science

Griffith University

Queensland, Australia

On Thu, Jun 23, 2011 at 2:44 AM, Ansley Manke <Ansley.B.Manke@xxxxxxxx> wrote:

Hi -
What you show looks like the right set of commands. Have you checked the 5-day data from your descriptor dataset, making sure that the time range is correct and that there's data? Making a few time-series plots or listing data at some locations is often a way to spot problems.

Do you see any messages when you go to use the regridded 1-day data? If for instance your original data is on a different calendar-type, then Ferret won't do the regridding operation.

Ansley

On 6/21/2011 5:16 PM, michael hughes wrote:
Hi All
I want to perform a linear interpolation on GCM data along the time axis. The existing data set is organised as separate files representing snapshots at 5 day intervals and I've created a Descriptor file to work with the data within Ferret. I want to interpolate these results from 5 day to 1 day.

From what I can gather this should be a rather trivial task, however I can't seem to get my code to work. When I plot the interpolated results the figure indicates that there is no valid data in the interpolated data set.

!--------------------------

use GCM_data.DES

LET var_5day = temp ! for example

! interpolate data along new time axis

DEFINE AXIS/t=25-JUN-1992:31-DEC-1999:1/UNITS=days tax_1day

LET var_1day = var_5day[Gt=tax_1day@LIN]

!-------------------------

The DES file used to import the data has a time axis at exactly 5 day intervals and I want the new axis to interpolate at 1 day intervals. However the output data set has no valid data.

Thanks in advance for you help,

Michael Hughes

PhD Candidate

Griffith University

Brisbane, Australia