[gradsusr] Gridding and Plotting Station Data

Wed Sep 22 14:35:40 EDT 2010

Thanks Jennifer! Yes, that's exactly the kind of information I need. I already had the idea that the key to the problem is the oacres() function. In fact, that's also the function that the recipe was using but the recipe wasn't very clear in explaining the purpose of wrf.dat and wrf.ctl. The GrADS documentation for the oacres() function wasn't very helpful for me either. 

I'll keep you posted on significant updates in our project. Again, thanks so much! 

Best regards, 

Nena 

----- Original Message -----
From: "Jennifer Adams" <jma at cola.iges.org> 
To: "GrADS Users Forum" <gradsusr at gradsusr.org> 
Sent: Wednesday, September 22, 2010 10:24:23 PM 
Subject: Re: [gradsusr] Gridding and Plotting Station Data 

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 

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Department Of Science & Technology 

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U.P. Campus, Diliman, Quezon City, PHILIPPINES 1101 

Tel No: +63 2 4269760 

Email: nena at asti.dost.gov.ph 

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IGES/COLA 
4041 Powder Mill Road, Suite 302 
Calverton, MD 20705 
jma at cola.iges.org 

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