[gradsusr] Land sea mask data, maskout

Andrew Friedman andfried at berkeley.edu
Fri Jun 6 03:23:39 EDT 2014

Hi Howard,

I believe these all should be possible using GrADS. Here are some initial general suggestions:

-For the initial graphing question, you use ‘set gxout grfill’ which plots the individual gridboxes without smoothing.
-The combination of ‘const’ and ‘maskout’ should allow you to plot land and sea separately.
-Finally, ‘lterp’ should allow you to interpolate between different gridbox sizes.

Others on the listserve may have additional ideas.


On Jun 5, 2014, at 4:33 PM, Howard Staines <metris at xtra.co.nz> wrote:

> Hi Andrew,
> 	Say along the Westcoast of the South Island you have ranges that
> rise up to 2000m within the 
> Space of a couple of km. The grid from contouring or shading is bleeds out
> into the sea and any coastal areas.
> What I was wanting to do in a 2stage process was ... using maskout() or
> similar ... stop that bleed out by
> Using a land sea mask to shade sea and land temps independently.
> Then using height in m from higher resolution topography adjust grid over
> the land surface adjusting using the gfs
> Height for grid point and adjusting temperature to actual height of
> topography.
> The question was relating to stage one the graph land 2m temp and seas 2m
> temp independent of each other 
> To remove the noise from higher topography on the lower areas 
> Well that's the idea
> Howard :) 
> -----Original Message-----
> From: Andrew Friedman [mailto:andfried at berkeley.edu] 
> Sent: Friday, 6 June 2014 10:23 a.m.
> To: info at metris.co.nz; GrADS Users Forum
> Subject: Re: [gradsusr] Land sea mask data, maskout
> Hi Howard,
> Can you please explain what you mean by enhancing the data? Are you looking
> for a type of interpolation?
> Andrew
> On Jun 5, 2014, at 1:58 PM, Howard Staines <metris at xtra.co.nz> wrote:
>> I am trying to enhance GFS temperature output 0.5 degree data.
>> We are dealing with a relatively small land mass (new Zealand) and I 
>> am trying to Enhance the data by stopping high terrain temp data 
>> affecting lower terrain as well as temperatures Over the sea.
>> I have been working with maskout(tmp,0.5 -landsfc) function but with 
>> 0.5 degrees its messy
>> Higher resolution resolution data 0.204 isnt working either due to 
>> resolution difference with Temp data.
>> Any clues as to a better way to go.
>> kind regards
>> Howard Staines
>> Manager
>> METRIS forecast systems 
>> P O Box 24, Featherston | ph 0800 372 433  | mailto:metris at xtra.co.nz   |
>> www.metris.co.nz  |
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