area average script question

[Teddy Allen]

Dear GrADS users,
I have taken the many tips from previous postings and external templates to produce a script that displays a time series of rainfall anomalies taken from the monthly GPCP dataset. The script works great as long as the geographic coordinates are relayed as a point location (ex: lat=3N, lon=6N), but, I am more interested in determining rainfall anomalies for average area regions (ex: lat=6N,lat=11N,lon=5W,lon=2E). 
 
I have tried to incorporate the GrADS command AAVE to calculate the area average, but I am not getting the desired results. Please see the below script for details:
 
'reinit'
*open gpcp monthly data file
'sdfopen c:\testdata\netcdf\precip.mon.mean.nc'
'set grid off'
'set grads off'
*create 12 x-axis labels; one for each month
'set t 1 12'
 
*define new variable to create monthly climatology for rainfall starting from Jan 1997
'define rainclim = ave(precip, t+216, t=347, 12)'
'modify rainclim seasonal'
'set t 1 last'
*define new variable for anomaly of monthly rainfall
'define anom = precip - rainclim'
*set time period for anomaly time series
'set t 336 347'
*define geographic point location to assess rainfall anomaly for the given time period
'set lat 8'
'set lon 1'
'd anom'
 
I would like to replace the set lat and set lon commands with:
'define region = aave(anom,lat=6,lat=11,lon=355,lon=2)
which should average rainfall anomaly for that area. I then change 'd anom' to 'd region', but nothing happens. Can anybody spot the error? Also, is there a problem when the x dimension varies from 0 to 360 and you are interested in the region from 357 to 1 (5W to 2E), obviously the order from 357 to 1 does not obey the proper value order? Has anybody else overcome issues with the AAVE command?
 
Thank you for your time.
sincerely,
teddy allen


 

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"To move quickly, go alone. To move far, go together."
African Proverb                                                                                                        *
 


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