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[ferret_users] active and break of monsoon



Hi,

I have a multiyear daily time series of precipitation data and I am strugling to create composite of active (and break) monsoon period.

I think what I need is a mask along the time axis that is based on a criteria (say area averaged precipitation >1 for 3 or more successive days). I can then apply the mask to create active phase composites for precipitation and other variables. Let me illustrate with an example: say daily area average precip are:

01-JUL-2007:  0.2.
02-JUL-2007:  0.8
03-JUL-2007:  1.2
04-JUL-2007:  2.1
05-JUL-2007:  2.0
06-JUL-2007:  1.5
07-JUL-2007:  1.1
08-JUL-2007:  0.4
09-JUL-2007:  0.1
10-JUL-2007:  0.6

From above definition definition: the active phase is from 3 - 7 Jul and what I want is a mask with 1 on those dates and undefined for other dates.

Other wish list are: to plot active days; get a list of just the valid days and finally save the mask for later use on other variables.

This is how far I have gone: For above example, I am able to creat a mask with 1's from 3-5 Jul but not able to extend it to 7 Jul.

let atv=if precip GT 1 AND precip[l=@SHF:1] GT 1 AND precip[l=@SHF:2] GT 1 then 1

list atv

01-JUL-2007:  .....
02-JUL-2007:  .....
03-JUL-2007:  1.0
04-JUL-2007:  1.0
05-JUL-2007:  1.0
06-JUL-2007:  ....
07-JUL-2007:  ....
08-JUL-2007:  ....
09-JUL-2007:  ....
10-JUL-2007:  .....

What do I modify if active period is to be valid only between 1 jul to 31 August

Many thanks in advance.

Jagadish

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