[gradsusr] What is the best approach when using two file sources when ... ?

[Jennifer Adams]

Hi, Howard -- 
The high res data will be slow to use over the internet, I suggest keeping a local copy of that data in your desired domain to avoid making your script any slower. Topo won't change, so grabbing it once may take some time, but then you have a local copy which will be easier to use. To interpolate the GFS data to that super-high grid, use lterp(). Then you can combine the two variables in an analysis expression (e.g. if you want to mask out GFS data based on the topo values.) It might be faster to first define the GFS data in a local grid so you only have to hit the server once to get the data. 

Haven't tested it or anything, but the expressions might look something like this:
ga-> define p = precip
ga-> d maskout(lterp(p,topo),topo-X) 

where X is the cutoff topo value. 


--Jennifer



On May 29, 2013, at 1:26 AM, Howard Staines wrote:

> Good afternoon fellow Grads users,
> 
> I want to use two different data sources 
> 
> 1, Opendap 	GFS 0.5 degree data for precipitation with 3hourly time
> steps
> 2, Opendap	high resolution topography one time step and I think about
> 8minute resolution.
> 
> The purpose is to use the 1 dataset for precipitation and freezing level
> calculation in meters and mask with 2, dataset using to display snowfall 
> Over high resolution topography.
> 
> My understanding is that you cant open these dataset as the aren't the same
> resolution and time step compatable. 
> 
> Do I combine the data and create a local file, would I need to use
> interpolation like re() function over the dataset nos 1.
> 
> Any assistance well.
> 
> Regards Howard Staines
> Metris Limited
> New Zealand
> 
> 
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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