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What do the numebrs mean?

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I have had my new Davis VP2 set up almost two weeks. It will be 2 weeks on Tuesday. Now my first check was when I had my LaCrosse and it got horrible checks and I am still seeing some hang over from that old station. Also I had a station down the street from me that had software issues so it was sending wrong data. It is slowly getting better though and the other station is working again. So now that I can get accurately checked I would like to know what the numbers mean and what I am suppose to be looking at.

So what does these numbers mean for this,

Average barometer error:    
Error standard deviation:    
Worst daily average barometer error:    
Worst daily standard deviation:    

What am I suppose to be looking at?


quoteBy default, the longer analysis periods display graphs that show the long term performance of this station. The graphs show the mean error over time, and include error bars which are one standard deviation long. This provides an easy way to see if there are any underlying trends in the data. Note that a 'step' in your data does not (necessarily) mean that something happened to your station. It could mean that another station came online in the local area, and they are changing the analysis.

If the error above is POSITIVE, then it means that the analysis temperature is HIGHER than the reported temperature. This means that your sensor is reading COLDER than expected.You can look at those for comparison purposes. The average difference between your station and each station below is listed as well. This may allow you to detect local stations which are erroneous. You can also use these numbers to adjust your instruments -- especially if a number of ASOS stations have similar differences to your station. Also, try increasing the analysis period to more than the default 28 days. The difference is only given if both stations report reasonably often during each day. Some stations only report every 6 hours, and this makes the average of less interest. In this case, the average is not displayed.

Your temps are failng.

I am not referring to the graphs, I am talking about the numbers below that. What exactly am I suppose to be looking at? What is my station and what is the others.

24 hours     Day time     Night time
Average temperature error   -2.2 F   -2.9 F   -1.8 F
Error standard deviation   1.3 F   1.3 F   1.0 F
Worst average temperature error   -2.7 F   -3.7 F   -2.4 F
Worst standard deviation   1.4 F   1.6 F   1.8 F

Is the average temperature error for my station or overall in my area? Worst average, Worst Standard etc what do those numbers mean and what should i be looking at and comparing. Most of what you listed I have read before from the Madis page but it doesn't help much If I do not know what I am looking at. It says "If the error above is POSITIVE, then it means that the analysis temperature is HIGHER than the reported temperature. This means that your sensor is reading COLDER than expected." Which error am I looking at "Error standard deviation"? If that is the case then I am 1.3 off then those in my area which is about right from what I have been noticing. So since that error if that is what I am looking at is positive that means it is running colder correct?

I don't think the temperature is failing. Like I mention in my first post. A lot of that I think is hang over from my old station and their is just not enough data yet to correctly process yet. If you look at the 28 days and the 3-7 days the errors below the temperatures are different. I get green thumbs up on all of them and 2 checks for Barometer and Dew Point/ Relative Humidity. I know the person 1.7 miles from me uses a Daytime FARS and most of the time my temp readings are 1+/- off from his. I am not real concerned about QC checks all that much especially with the numbers being that close and you have to take into consideration of Micro Climates. I just would like to know what the numbers above mean and what I am looking at and suppose to be looking at so I can detect a problem in the furture should one arise.

Here is the 7 day data. Compare it to the 28 day and you will see what I am talking about. The numbers are more within range which is why I think it is Hang over form the old station which were sending these errors to start with. Would this be a correct assessment? I think once I get some more time under this new station things should level out.;days=7#Data

Those numbers are your station in comparison with a group of others around you, but not necessarily the ones listed at the bottom of the page.  There is no way that I've found to know which stations are actually used in the computation.  Apparently a closely held MADIS secret.  My guess though is that they're probably in the equation.

When you look at the longer time periods yes, your old station readings will have an effect and that will diminish with time.  I like to look at a short period like 3 days because I figure I'll notice problems quicker that way.

As for standard deviation, you can google that just like I did and it probably still won't mean much to you.  It's something for statisticians that completely goes over my head.

- Jim


--- Quote from: jmcmurry on March 09, 2008, 11:12:38 AM ---Those numbers are your station in comparison with a group of others around you, but not necessarily the ones listed at the bottom of the page.

--- End quote ---

Thanks, I had heard they compare them to others around you. Do you know which numbers are your station and which are the group they are comparing them to are all of them your station? Which ones should I be more concerned with and be comparing.

I know this guys software has been messed up. He use to pass everything and he is the closest station to me, but has you stated that probably means nothing. His numbers are way off the chart compared to mine when it comes to temps. The more I look at things I should be looking at the Average temperature error correct? The rest is just stats right


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