[wxqc] MADIS explanation needed

[Philip Gladstone]

Lew

If you mouse over the red 'X' you will get an explanation of the reason. 
Typically the green check / red x are a little more strict than the 
thumbs ratings. Also, the thumbs ratings are more heavily weighted 
towards recent observations.

In a nutshell, the thumbs represent the percentage of observations that 
pass the MADIS checks. These are quite coarse (2 mbar, 6 degrees F for 
temperature etc), but do a good job of ruling out really wacky readings.

The red/green classification is a tighter set of checks, but is based on 
the average over the analysis period (normally 28 days unless you 
clicked on one of the embedded links to change it). Thus, you might get 
a red X for pressure if your pressure tracked the analysis well, but 
with a constant offset, and the offset was large enough (say 1.5 mbar). 
it could be that none of your readings fail MADIS checks, but 
nevertheless, they are unlikely to be 'right' (for some value of right).

For temperature, a separate analysis is done for daytime readings and 
nighttime readings (omitting the hour before and after sunrise and 
sunset). This allows the system to spot problems like solar heating.

The yellow question mark means that the location check failed (and it 
would have displayed a red cross). The problem may be that the analysis 
is being performed for a location other than the actual observing 
location. This will obviously cause a problem.

[Now I reread your message, I don't understand the yellow question mark 
for KLVN -- it looks like some sort of display problem. When I get back 
home, I'll fix this one.]

Philip

webmaster wrote:
> Gerry,
> 
> It would be nice if we could get an official response from the 
> programmers.  It isn't my station that has the two thumbs up and a 
> big red X, it is the local AWOS station.
> 
> I thought the thumbs up or down rating were affiliated with the 
> symbol above them, apparently not.
> 
> It would be nice if there was some documentation (and maybe there is) 
> that explains what the symbol on the top is and how it differs from 
> the thumbs below.  In my mind a big red X is like getting an "F".  My 
> teachers never wrote in "RED" unless you flunked...so it seems like 
> an oxymoron to have a big red X AND two thumbs up.  So apparently the 
> big red X is the rating of something different than the two thumbs up 
> below that???  I don't know why there are two ratings for one item 
> and how the results could be so different.  the AWOS site is the only 
> site where I have seen the big red X.  They also have a yellow 
> question mark on another item and I haven't seen that before either.
> 
> Thanks,
> 
> Lew
> 
> 
>> Message: 1
>> Date: Wed, 09 Apr 2008 22:36:04 -0500
>> From: Gerry Creager <gerry.creager at tamu.edu>
>> Subject: Re: [wxqc] Questions regarding my MADIS data..
>> To: Discussion of weather data quality issues
>>     <wxqc at lists.gladstonefamily.net>
>> Message-ID: <47FD8B24.4000509 at tamu.edu>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Lew,
>>
>> It's not uncommon for me to get 2 green thumbs and a red X for humidity,
>> but I'm in a different microclimate than my surrounding stations.
>>
>> The QC checks are an indicator to aid in evaluation.  If you're passing
>> MADIS checks, your data are getting used by a lot of folks.
>>
>> gerry
> 
> ******************************************
> Lew - Amateur Weatherman
> lew at farmingtonweather.com
> Farmington Weather
> www.farmingtonweather.com
> Farmington, Minnesota, USA 
> 
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