[Thread Prev][Thread Next][Index]

# Re: [ferret_users] annual totals from monthly time series

```Hi Andy,
```
The problem as I'm sure you know is that a "year" isn't the same length every year in the standard calendar. Have a look at this example from the Users Guide: (See "monthly axis, creating" in the index). It defines a true monthly axis with edges at the exact start of each month, which is similar to what you want to do. I imagine you can adapt it to create the true year axis that you want.
```
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/commands-reference/DEFINE#_VPINDEXENTRY_1311

```
Write back if it doesn't see to work for some reason (or if it does, fill us in on the details!)
```

Ansley

Andy Jacobson wrote:
```
```Howdy,

```
I'm trying to compute annual means from monthly time series. My strategy has been to define a time axis with yearly resolution, then regrid to this time axis using the @ave transformation, like:
```
```
define axis/edges/t="01-Jan-2000:00:00:00":"01-Jan-2008:00:00:00":1/UNITS=years tannual
```list nee[gt=tannual@ave]

```
The regridding strategy works. The only problem I have is that I'd like the tannual axis edges to each fall right on 01-Jan 00:00 UTC, but they drift as shown by the TBOXLO values below:
```
show axis/l=1:9 tannual
name       axis              # pts   start                end
```
TANNUAL TIME 9 r 01-JUL-2000 14:54 01-JUL-2008 13:28
```T0 = 15-JAN-1901
Axis span (to cell edges) = 9

```
L T TBOX TBOXLO TSTEP (YEARS) 1> 01-JUL-2000 14:54:36 1 01-JAN-2000 00:00:00 99.46165 2> 01-JUL-2001 20:43:48 1 31-DEC-2000 05:49:12 100.4616 3> 02-JUL-2002 02:33:00 1 31-DEC-2001 11:38:24 101.4616 4> 02-JUL-2003 08:22:12 1 31-DEC-2002 17:27:36 102.4616 5> 01-JUL-2004 14:11:24 1 31-DEC-2003 23:16:48 103.4616 6> 01-JUL-2005 20:00:36 1 31-DEC-2004 05:06:00 104.4616 7> 02-JUL-2006 01:49:48 1 31-DEC-2005 10:55:12 105.4616 8> 02-JUL-2007 07:39:00 1 31-DEC-2006 16:44:24 106.4616 9> 01-JUL-2008 13:28:12 1 31-DEC-2007 22:33:36 107.4616
```
I had hoped that I could specify the axis edges explicitly as in:

```
define axis/edges/t tannual={"01-Jan-2000:00:00:00","01-Jan-2001:00:00:00","01-Jan-2002:00:00:00","01-Jan-2003:00:00:00","01-Jan-2004:00:00:00","01-Jan-2005:00:00:00","01-Jan-2006:00:00:00","01-Jan-2007:00:00:00","01-Jan-2008:00:00:00"}
```
...but ferret (v5.70 alpha, on OSX) emits:

```
**ERROR: illegal data type (float,string,...) for operation: {"01-Jan-2000:00:00:00", ...
```
So:

(1) Is there a way to explicitly specify the dates of a time axis?
(2) Am I thinking unferretly about how to compute annual totals?

Thanks!

Andy

```
```
```

[Thread Prev][Thread Next][Index]

Contact Us
Dept of Commerce / NOAA / OAR / PMEL / TMAP

Privacy Policy | Disclaimer | Accessibility Statement