time series

[Charles Seman]

Sachin,

Please find attached a GrADS script "ta_maskout.gs" in which three
methods for calculating time series of area-averaged temperature "ta"
are compared.  The script defines a limited region to omit from the
area-averages.  Method 1 follows a technique sent to GrADS Listserv on
12/6/2007 by Jayakrishnan PR (uses "asum" rather than "aave").  Method 2
defines a new "tanew" field for all time levels in which the temperature
values have been redefined to "undef" (via GrADS "defval" and "maskout")
after which the area-average is then calculated with "aave" using
"tanew".  Method 3 uses a predefined external "mask" file (generated
using "ta_mask.gs", attached) to compare with the results from Method 2
(which uses internal "mask" defined using "defval" and "maskout" to
generate "tanew") and also to compare to Method 1 (which uses "asum" to
subtract "ta" sums).  In summary, Methods 2 & 3 showed no differences in
results, while the differences between Methods 1 & 2 for the limited
region area-averages were comparable to differences obtained using
"aave" vs "asum" for the total domain (please see "ta_maskout.pdf";
attached).  ("pause.gsf" GrADS script function also attached)

I hope this helps... Please let me know if you find any problems and/or
have any questions about the scripts or results...

Thanks,
Chuck

Sachin Ghude wrote:
>
> Dear all,
>
> Would somebody please advice me for the following problem:
>
> I want to plot a time series averaged over the "lat -20 20,lon 0
> 360" region which will not include surface temperature data over the
> region "lon=110 150,lat=0 20" while calculating the average.
>
> In other words, I want to set region between "lon 110 150, lat 0 20"
> to missing values while plotting the time series avereged over the
> region "lat -20 20,lon 0 360" .
>
>
> Sachin D Ghude
>
> *---------- Original Message -----------*
> From: louis Vonder
> To: GRADSUSR at LIST.CINECA.IT
> Sent: Fri, 7 Dec 2007 15:42:49 +0100
> Subject: RE : time series
>
> > Hi,
> >
> > set lon 0 360
> > set lat -20 20
> >
> > d ave(sst, t=tmin,  t=tmax)
> >
> > Perhaps this can help you
> >
> > */Sachin Ghude /*a écrit :
>
>     dear all,
>     >
>     > I am trying to plot a surface temperature time series averaged
>     over the region
>     > lon=0,lon=360,lat=-20,lat=20. I am using following function:
>     >
>     > 'd tloop(aave(maskout(t,t),lon=0,lon=360,lat=-20,lat=20))'
>     >
>     > would somebody please advice me how to plot a time series
>     averaged over the above
>     > region which will not include surface temperature data over the
>     region
>     > lon=110,lon=150,lat=0,lat=20 while calculating the average.
>     >
>     > Sachin D Ghude
>     >
>
>
> >
> >
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--

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

********************************************************************
 Charles Seman                                Charles.Seman at noaa.gov
 U.S. Department of Commerce / NOAA / OAR
 Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
 201 Forrestal Road                              fax: (609) 987-5063
 Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
********************************************************************

"The contents of this message are mine personally and do not reflect
any position of the Government or NOAA."

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