[Wrf-users] Comparing U,V 10 meters to observations

[Hacker, Joshua (Josh) (CIV)]

Apologies to those who know this better than I do, but this is an
interesting question...

 

Unless you do something fancy, the WRF outputs instantaneous grid-point
values, regardless of your output interval.  Those values are filtered
non-trivially by some function of implicit and explicit diffusion in the
model (think physics, damping, time and space discretization, etc).
Therefore there is no one answer to your question.  

 

In practice (I believe) most people just compare directly to 10-min
averaged wind obs (WMO standard), or 2-min averaged wind obs (USA) but
in my opinion 2 minutes is usually too short to be fair.

 

One approach to getting at the averaging in the model is through data
assimilation and statistical consideration of observation error levels
when the error may be dominated by representativeness error (difference
between scales represented in obs and model).  Others have looked in
spectral space to get an idea of the averaging scales.

 

The other thing that you might consider, if you have the data to do it,
is to compare WRF forecasts with obs averaged over many different time
lengths (or alternatively band-pass filtered).  Then you can get a more
complete picture of what time scales it can or cannot predict with
skill, and decide whether it is doing what you hope.

 

That said, I'd be interested in hearing any other comments from the
community and especially our verification gurus - is there any
"conventional" wisdom or rules of thumb that folks are using or that
have recently shown promise, empirically?  Have I missed something?

 

Sorry that there is no simple answer.

 

Josh

 

________________________________

From: wrf-users-bounces at ucar.edu [mailto:wrf-users-bounces at ucar.edu] On
Behalf Of Juan Gonzalez
Sent: Tuesday, January 26, 2010 12:33 PM
To: wrf-users at ucar.edu
Subject: [Wrf-users] Comparing U,V 10 meters to observations

 

Hi everyone,

 

I am interested on validating the WRF 10m wind forecast with
observational data. I would like to know what is the corresponding
average scale for the WRF 10m winds, that is, do the correspond to
1-minute, 10-minute average winds or what kind of average, if any?

 

My WRF configuration outputs wind every 3 hours.

 

Thanks for your help, 

Juan Gonzalez 

-- 
Juan O. Gonzalez
Research Assistant - Caribbean Integrated Coastal Ocean Observing System

Graduate Student - Physical Oceanography
Marine Sciences Department
University of Puerto Rico - Mayaguez Campus

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