5 day precipitation

[Ben Burford]

Hello All,

I'm trying to implement a script.  I studied functions (e.g. tloop) and look
ed in the archives for help, but so far its over my head as a beginner, I'm
not even sure if Grads can do this.

I have an 8 year (t=1,2922) global gridded daily precipitation data set.  Fo
r each grid cell I want to go through the time series and check each five da
y period (2918 possible 5 day periods) to see if the total of the precipitat
ion for the five days is greater than a certain level, if it is I want to in
crement a counter.  The result will be a single value (total count) for each
 grid cell (global grid of a single value per grid cell).

The value that I want to check the five day total against is "10% of the ann
ual average rainfall" (tenpanave) which I'm calculating as follows (add up a
ll the daily values for 8 years, divide by 8 to get the annual average, then
 take 10% of that):
tenpanave = 0.1*((sum(prec,t=1,t=2922))/8)

A flow chart for the script might look like:
* Calculate "10% of the annual average rainfall" (tenpanave)
tenpanave = 0.1*((sum(prec,t=1,t=2922))/8)

* calculate the precipitation over 5 days (5dayprec), if that 5 day total is
 greater than or equal to ten percent of the annual average precipitation (t
enpanave) for that grid cell, then increment the counter for that grid cell.
  Perform this process for all grid cells, over the full time period of 2922
 days (x from 1 to 2918).
x=1
5dayprec=sum(prec,t=x,t=x+4)
if 5dayprec is greater than or equal to tenpanave then count=count+1
x=x+1
if x=2919 then quit, else go up three steps and calculate the next 5 day win
dow (5dayp)

* Display results
d count


As I say, I don't know if this can be done with Grads.  Any help would be gr
eatly appreciated.

Thank you,

Ben