[gradsusr] Gridding and Plotting Station Data

Wed Sep 22 10:24:23 EDT 2010

Yaquiang: Please don't use the GrADS forum to promote MeteoInfo.

Nena: I haven't looked at the specific recipe you refer to; however,  
in order to draw a contour plot in GrADS that is based on station  
data, you use the oacres() function, which transforms the station data  
to a gridded field so that the contouring algorithm will work. The  
oacres() function requires a grid expression -- the data in the grid  
is ignored, it is just the grid information that is used to perform  
the transformation. My guess is that the wrf forecast data referred to  
in the recipe is merely there to provide a grid to interpolate to. You  
don't need WRF data to do this, you can create a dummy descriptor file  
that points to a fictitious data file but that should be sufficient  
for oacres() to work.

The dummy descriptor (foo.ctl) would look something like this:
dset ^foo.dat
options template
undef -9.99e8
title foo
xdef  ...
ydef ...
zdef 1 linear 1 1
tdef 1 linear 1jan0001 1dy
vars 1
foo 0 99 foo
endvars

You would have to define the XDEF and YDEF entries to create a lat/lon  
grid that covers the area of your station observations, and has a  
resolution reasonably close to the density of your observational data.  
I would set the TDEF to match your station data set too. The 'options  
template' entry is necessary so that GrADS doesn't try to open  
foo.dat. You can open this dummy descriptor with GrADS, then use 'lon'  
or 'lat' (internally defined variables that contain the longitude/ 
latitude values of the grid) as your grid expression in oacres. Your  
GrADS commands might look something like this:

ga-> open foo.ctl
ga-> open station.ctl
ga-> set gxout contour
ga-> d oacres(lon.1, var.2)

I hope this is the kind of help you were looking for.
--Jennifer

On Sep 22, 2010, at 6:00 AM, Yaqiang Wang wrote:

> You can use MeteoInfo software to visualize AWS observation data.
> ASCII format data were also supported. The software could be
> downloaded freely from the website http://www.esnips.com/web/MeteoInfo
> . The documents on the website will help you to use it.
>
> Yaqiang
>
> 2010/9/22 Nena Carina Española <nena at asti.dost.gov.ph>:
>> Hi John. Thanks for the reply.
>>
>> The recipe was derived from the operational procedure of Brazil and  
>> we
>> wanted to adopt a similar procedure for the Philippines. I am from  
>> the IT
>> sector so I'm really new to all of these. What I actually wanted to  
>> ask
>> about is the numerical model data itself. I don't have that. I only  
>> have
>> observed data from AWS network. Can I actually use the wrf.dat that  
>> came
>> with the recipe or do I have to create my own from WRF? :-)
>>
>> What our team wants is to be able to visualize the hourly data we  
>> have for
>> temperature, humidity, pressure, wind speed, wind direction, solar
>> radiation, and hourly rain. But our priority is pressure, wind  
>> speed, and
>> wind direction. If you know of other techniques/recipes that I  
>> could follow
>> please let me know.
>>
>> Thanks and BR,
>>
>> Nena
>>
>>
>> On Tuesday, 21 September, 2010 07:40 PM, Huddleston, John wrote:
>>
>> Nena
>>
>> run 'grads -l'
>> open wrf.ctl
>> set gxout shaed
>> set csmooth on
>> d slvl.1
>>
>> and you will see the background color as shown in the example
>>
>> set lon -43.75 -43.1
>> set lat -23.1 -22.7
>> d slvl.1
>>
>> and it zooms into the area where the data points can be plotted
>>
>> John Huddleston, PhD
>>
>> ________________________________
>> From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org]  
>> On
>> Behalf Of Nena Carina Española [nena at asti.dost.gov.ph]
>> Sent: Tuesday, September 21, 2010 12:24 AM
>> To: GrADS Users Forum
>> Subject: [gradsusr] Gridding and Plotting Station Data
>>
>> Hi Guys,
>>
>> First of all, I'm not a meteorologist so pardon me if my questions  
>> here
>> might sound silly to you. :-)
>>
>> I need help with Recipe-013: Gridding and Plotting Station Data.  
>> What I need
>> to do is to be able to plot contour maps from hourly AWS data, just  
>> like
>> what was done in Recipe-013. However, I won't be plotting just
>> precipitation. I'll just start out with pressure. Later on if I  
>> already know
>> the ins and outs of this recipe, I'll be creating plots for other  
>> variables
>> such as temperature, wind speed, and wind direction.
>>
>> We have a team in charge of parsing the information from AWS and  
>> could feed
>> me data that's already been formatted to what Recipe-013 requires.  
>> Following
>> the recipe, I was able to create a control file and binary that  
>> GrADS could
>> read. What I don't understand is the wrf.dat and wrf.ctl that the  
>> recipe is
>> using. The recipe says it "contains any forecasted variable and, most
>> important, the information of the grid we want the station data to be
>> gridded to." Can someone explain this further to me? I was only  
>> asked to
>> plot actual data, no forecasting or whatsoever. :-)
>>
>> Thanks and regards,
>>
>> Nena
>>
>>
>> _______________________________________________
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>>
>>
>> --
>> GRID OPERATIONS TEAM
>> Advanced Science & Technology Institute
>> Department Of Science & Technology
>> ASTI Bldg., C.P. Garcia Ave., Technology Park Complex
>> U.P. Campus, Diliman, Quezon City, PHILIPPINES 1101
>> Tel No: +63 2 4269760
>> Email: nena at asti.dost.gov.ph
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>>
>
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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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