[ferret_users] Re: How to extract DJF average time series from a monthly time series?

["\"STEEVEN PAUL\" \"YERRAGUNTLA\"" <steevenpaul@xxxxxxxxx>]

Dear ferreters,
          I could find the answer to my question from few threads in Archives.  I got major help from the the following thread  http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2009/msg00211.html and thanks to Peter.

The ferret script as follows

---------------------------------------------------------
use SST.nc
!With the mod function we create a mask for all the Decembers, Januarys and Februarys.
let month=l[gt=sst]

let DJF = if (mod(month,12) le 2) OR (mod(month,12) le 2) then 1

!Now we need to place this mask onto our data on a monthly axis.
let wintersst=sst[d=1]*DJF 
list/x=60/y=15  wintersst

!club the DJF values together

let sst_compr = COMPRESSL(wintersst)
list/x=60/y=15  sst_compr

 ! 1870-2010 --> 140 years --> 140*3=420 data points
     ! we need to average this data points in pairs of 3 to find the
     !  seasonal mean. Easy way is to use two abstract axes, one

     !  with 33 points (ranging from 1-420) and another one with
     !  11 points (ranging from 2-419) and regrid using @AVE.

!defining to abstract axes one to put the data on the time axis another is to average the DJF months

define axis/t=1:420:1 t420
let sst_djf_all = sst_compr[gt=t420@ASN]
list/x=60/y=15 sst_djf_all

define axis/t=2:419:3 t11
let sst_djf_av = sst_djf_all[gt=t11@AVE]

define axis/t=1870:2010:1/units=years tyear

let sst_djf = sst_djf_av[gt=tyear@ASN]
list/x=60/y=15 sst_djf

set var/title="DJF sesonal mean SST"/units="degC" sst_djf

!saving the extracted data to a ncfile for future purpose


sp rm -f sst_djf_mean.nc
save/file=sst_djf_mean.nc/append sst_djf

------------------------------- END OF THE SCRIPT ---------------------------------------------------

On Mon, Oct 11, 2010 at 6:42 PM, steeven paul yerraguntla <steevenpaul@xxxxxxxxx> wrote:

Dear ferreters,
       I want to extract the DJF months time series in the following format.
       15-dec-1980
       15-jan-1981
       15-feb-1981
       15-dec-1981
       15-jan-1982
       15-feb-1982
             ----
         and so on
I tried to follow the examples in archives, provided by Jaison Kurian and Ansley which are for extracting JJA months and i could not get time series for DJF months though making some changes to the scripts. Hope someone will help me in this connection.    Ansley's  Scripts as follows
--------------       -----------------            ---------------------------------------           ------------------------------------------

use monthly_navy_winds
let nmon = `uwnd,return=Lend`
let tt = t[t=1:`nmon`]
let june = if mod(tt,12) ge 6 then tt
let june_aug = if mod(june,12) le 8 then june
list june_aug

! The number of summer months.
let nja = `june_aug[t=@ngd]`

let just_summer = compressl(june_aug)
list just_summer[L=1:`nja`]

! Now sample the Lth point of uwnd for the summer months
let uwnd_jja = samplel(uwnd,just_summer[l=1:`nja`])

! Define a calendar axis containing these months.
def axis/t0="`uwnd,return=t0`"/units="months" tsummer = just_summer[l=1:`nja`]

! Put the sampled summer data on the calendar axis
let uwnd_summer = uwnd_jja[gt=tsummer@asn]
list/x=180/y=0 uwnd_summer

--------------------------------------------------------------- end of script --------------------------------------------------------------------------------------------------

Thanks in advance,


 

--
Steeven Paul Y
Research Fellow
NIO RC Vizag
176 Lawsons Bay Colony
Visakhapatnam - 530017

-- 
Steeven Paul Y
Research Fellow
NIO RC Vizag
176 Lawsons Bay Colony
Visakhapatnam - 530017