Re: [Ferret] calculate climatologies from multiple LARGE files

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Zhen,
Bill answered the original question, suggesting descriptor files, which 
is exactly the right answer to the question.  Then Zhen ran into a 
difficulty creating the climatology, because his data is on a Julian 
calendar, and the monthly_climatology time axes use a Gregorian 
calendar.  (Relevant topics in the Users Guide are "Climatology", 
"Calendar, axis, discussion", "modulo, regridding")

There are two possible solutions:

1) create your own climatological axis having a Julian calendar, and use 
@MOD to regrid to that axis.

or

2) regrid the data to a Gregorian calendar, and then apply the modulo 
regridding and regrid to month_reg

I think I'd recommend the first option, creating a Julian climatological 
axis. This will require less interpolation. A climatological axis is one 
which spans one year or less, and has dates in year 0000 or 0001.  It 
has the /MODULO qualifier.  A regularly-spaced monthly climatological 
axis can be defined as:

DEFINE 
AXIS/MODULO/CALENDAR=julian/EDGES/t0="1-jan-0000"/t="1-jan-0000":'31-dec-0000":1/units=months 
jul_month_reg

I use the /EDGES qualifier to specify that the start and end I am giving 
refer to the edges of the grid cells; this means that the axis 
coordinates are centered at the middle of each month.  (An example of 
defining an irregular monthly axis is in the Users Guide under "define 
axis, /EDGES"

Now you can do

let temp_clim=temp[d=1,GT=jul_month_reg@MOD]

zhen.li@gsfc.nasa.gov wrote:

> Bill:
>
> Thank you very much for your help. I got the descriptor file created 
> by using the perl script, make_des.
>
> When calculating the climatology using the des file, I found that my 
> yearly data can
> not be regridded to the monthly climatology because the yearly data is 
> on Julian calendar.
>
> Here is all my text output from ferret section:
> ============================================================================= 
> yes? use temp_6484
>  *** NOTE: netCDF bounds variable definition error
>  *** NOTE: Bounds definition "time_bounds" points to no existing axis
>  *** NOTE: Ignoring BOUNDS attribute
>  *** NOTE: netCDF parent axis definition error
>  *** NOTE: Edges definition "zt_edges_ocean" points to no existing axis
>  *** NOTE: Edge definitions ignored
> yes? show data
>      currently SET data sets:
>     1> ./temp_6484.des  (default)
>  name     title                             I         J         
> K         L
>  TEMP     Potential temperature            1:700     1:390     
> 1:43      1:252
>
> yes? use climatological_axes
>  *** NOTE: regarding /home/zhenli/ferret/go/climatological_axes.cdf ...
>  *** NOTE: Climatological axes SEASONAL_REG, MONTH_REG, and 
> MONTH_IRREG defined
> yes? let temp_clim=temp[d=1,GT=month_reg@MOD];
> yes? list temp_clim
>  **ERROR: regridding:  only @ASN, @LIN, or @NRST regridding between 
> calendar types: JULIAN, GREGORIAN
> =============================================================================== 
>
> My "temp_6484.des", looks like this:
>
>
> ################################################################################# 
>
> &FORMAT_RECORD
>    D_TYPE             = '  MC'
>    D_FORMAT           = '  1A'
> /
>
> &BACKGROUND_RECORD
>    D_TITLE            = 'pacific ocean exp'
>    D_T0TIME           = '01-JAN-0001 00:00:00'
>    D_TIME_UNIT        = 86400
>    D_TIME_MODULO      = .FALSE.
>    D_CALTYPE          = 'JULIAN'
> /
>
> &MESSAGE_RECORD
>    D_MESSAGE          = ' '
>    D_ALERT_ON_OPEN    = .FALSE.
>    D_ALERT_ON_OUTPUT  = .FALSE.
> /
>
> &EXTRA_RECORD
> /
>
> &STEPFILE_RECORD
>    S_FILENAME         = 'temp_1964.nc'
>    S_AUX_SET_NUM      = 0
>    S_START            = 717000.5
>    S_END              = 717335.5
>    S_DELTA            = 30.4545454545455
>    S_NUM_OF_FILES     = 1
>    S_REGVARFLAG       = ' '
> /
>
> &STEPFILE_RECORD
>    S_FILENAME         = 'temp_1965.nc'
>    S_AUX_SET_NUM      = 0
>    S_START            = 717366.5
>    S_END              = 717700.5
>    S_DELTA            = 30.3636363636364
>    S_NUM_OF_FILES     = 1
>    S_REGVARFLAG       = ' '
> /
>
> Here is my script:
> yes? use temp_6484
>  *** NOTE: netCDF bounds variable definition error
>  *** NOTE: Bounds definition "time_bounds" points to no existing axis
>  *** NOTE: Ignoring BOUNDS attribute
>  *** NOTE: netCDF parent axis definition error
>  *** NOTE: Edges definition "zt_edges_ocean" points to no existing axis
>  *** NOTE: Edge definitions ignored
> yes? show data
>      currently SET data sets:
>     1> ./temp_6484.des  (default)
>  name     title                             I         J         
> K         L
>  TEMP     Potential temperature            1:700     1:390     
> 1:43      1:252
>
> yes? use climatological_axes
>  *** NOTE: regarding /home/zhenli/ferret/go/climatological_axes.cdf ...
>  *** NOTE: Climatological axes SEASONAL_REG, MONTH_REG, and 
> MONTH_IRREG defined
> yes? let temp_clim=temp[d=1,GT=month_reg@MOD];
> yes? list temp_clim
>  **ERROR: regridding:  only @ASN, @LIN, or @NRST regridding between 
> calendar types: JULIAN, GREGORIAN