[wxqc] Comparing stations

Ted Lum gladstonefamily45.net at tedlum.com
Sun Oct 30 11:34:07 CDT 2011

You have to remember the Philip takes an analysis line from MADIS and 
makes his own determination. MADIS just gives out the analysis line, it 
does not make any determination. Philip has set some threshold at which 
point the software on his site displays that message. You'll often see 
that he and MADIS disagree on what is bad data, and both are displayed 
for that purpose. If anything it should probably be worded in a less 
absolute way. But regardless of any of the quality metrics they are 
simply metadata, the data record is kept.

Also, for clarification, I said "..but it does take out flawed 
readings." It does not take the data out of the data set, it takes it 
out of the analysis; if the data is suspect it won't be used as part of 
the Spatial Consistency check. That is bad wording, actually the data 
won't be removed it will just not be considered.

On 10/30/2011 12:15 PM, Paul Grace wrote:
> "MADIS does NOT throw out any data at all."  Ah.  I interpreted "Your 
> readings are not within an acceptable error range" as the data was not 
> acceptable.  The temp analysis is often wrong for my location by 20F, 
> and the dew point analysis is similarly horked.  It's humorous-
> ------------------------------------------------------------------------
> *From:* wxqc-bounces at lists.gladstonefamily.net 
> [mailto:wxqc-bounces at lists.gladstonefamily.net] *On Behalf Of *Ted Lum
> *Sent:* Saturday, October 29, 2011 21:27
> *To:* Discussion of weather data quality issues
> *Subject:* Re: [wxqc] Comparing stations
> Not flawed in that sense. It checks for stuck sensors. It checks for 
> bounds; temperature must be between -60 and +130 for example. It 
> checks for Temporal Consistency; temperature can't vary by more than 
> 35 F/hour for example. It does an Internal Consistency check; Dew 
> Point Temperature can't exceed Air Temperature for example. And it 
> does the Spatial Consistency check but we don't know what station(s) 
> it uses when.
> Most of all MADIS does NOT throw out any data at all. Worst it ever 
> does is flag it with the checks it failed.
> On 10/29/2011 10:25 PM, Paul Grace wrote:
>> Right.  I think it's not very good at determining what is "flawed" 
>> when looking at data that has no close neighbors.  It exhibits a 
>> tendency to throw out the very data that it most needs to fill in its 
>> holes.
>> *From:*wxqc-bounces at lists.gladstonefamily.net 
>> [mailto:wxqc-bounces at lists.gladstonefamily.net] *On Behalf Of *Ted Lum
>> *Sent:* Saturday, October 29, 2011 19:13
>> *To:* Discussion of weather data quality issues
>> *Subject:* Re: [wxqc] Comparing stations
>> Well, we don't really know what MADIS includes so we can't say if it 
>> does that or not, but it does take out flawed readings. Someone at 
>> NOAA ESRL/GSD might be able to say how the algorithm works; I've 
>> never seen it as anything but a black box.
>> On 10/29/2011 7:34 PM, Paul Grace wrote:
>> I would guess that data should be accepted into the model, **unless** 
>> it has a nearby data (hundreds of feet, not hundreds of miles) with 
>> which it does not agree, or exhibits flaws such as stuck, zero, over 
>> limit, sensors, etc.
>> *From:*wxqc-bounces at lists.gladstonefamily.net 
>> <mailto:wxqc-bounces at lists.gladstonefamily.net> 
>> [mailto:wxqc-bounces at lists.gladstonefamily.net] *On Behalf Of *Ted Lum
>> *Sent:* Saturday, October 29, 2011 15:32
>> *To:* Discussion of weather data quality issues
>> *Subject:* Re: [wxqc] Comparing stations
>> AFAIK Philip takes the nearest 10 or so. MADIS has its own way of 
>> doing things. I'd put it back on you and ask what would you like it 
>> to do? Nothing can really invent stations and data where there isn't 
>> any, nor can it manufacture a particular type of data. So there is no 
>> other data near you, and no other data that has the same profile as 
>> you. What exactly is it that you want?
>> On 10/29/2011 4:33 PM, John M. Markle wrote:
>>   Not sure what going on here and as always when I ask something on 
>> wxforums I get ingored so I really  don't expect an answer here either.
>>  Why are station that are 150 miles to 500 miles from me listed on my 
>> summa ry page for comparsion. This is totally useless to me and I ame 
>> sure it is also would be useless to anyone else also. Another thing I 
>> notice some of these
>> stations are under Continetal influces where I am under maritime 
>> influences. Seem to be one would want to be compared to station in 
>> one own enviroment. On this list the first station  listed is 150 
>> miles from me and the last one is 504 miles. Just 140 miles shy of 
>> Seattle, Washington.  Other thing I notice is that they are all PWS 
>> stations. Too me this is the poorest choice to use for comparison as 
>> most PWS owner  just throw their station up and walk away. As long as 
>> it seems to be close it is good enough for them.
>>  Here is the link. http://weather.gladstonefamily.net/site/D1453
>>  Like I said I don't expect an answer but thought I try any ways.
>> John

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