Topic: Wind Speed Error ????

[prkguy]

http://weather.gladstonefamily.net/cgi-bin/wxqual.pl?site=D4210

Good evening everyone.   If I am reading my quality report correctly it seems that my recorded winds speeds are on the high side.     

Am I interpreting it correctly?      Is this something I need to be worried about?     I do have my anemometer set at 27' so maybe I should expect my winds speeds to be higher.    Im not sure what to think.  Any ideas?    Mike

[SlowModem]

Am I interpreting it correctly?      Is this something I need to be worried about? 

Mike,

Of the variables that you report, rainfall and wind speed are the two that can vary the most in short distances.  I really don't know how they can determine that your windspeed is off.  I guess they look at averages.  It seems to me the terrain and forestation, etc., would make it difficult to compare to other  stations.  I'm sure some of the smart guys around here can give you a more detailed answer, but I wouldn't worry too much about it.

Greg

[prkguy]

Greg I checked a couple of other stations in the area and their wind speed also seems to be higher than the norm.   I guess I wont worry too much about it right now.  Thanks.  Mike

[Bearcage]

Mike,
   I just looked at your latest qc for windspeed on your link and your avg speed is 4mph to low.A positive 4 on the graph means the qc value was 4mph higher than your average which makes your avg 4 mph low.Many variables can affect your avg wind.terrain(trees,buildings),accuracy of your equipment,your software sampling rate.I own VWS software and my qc said my avg speed was always 1.5-2.0 mph low.I switched to WUHU because i believe VWS/CWOP wxreport.txt file was converting to knots resulting in the error.
                                              GB

[George Richardson]

Mike,
CWOP is a good reference TOOL. It is not the gospel. Search the forum for other discrepancies. Davis is not infallible but I will bet on them over CWOP on a specific issue.
JMO
George

[prkguy]

Below is a quality control report e-mail that I found in my in-box this morning.   I think the error must be in the wind speed.    I have a lot more reading to do so I can learn how to interpret their findings.      Mike



DATE     UTC         *   ALT       * POT TEMP *  DEW PNT  *    DD       *    FF   
                           *   (MB)     *  (DEG F)    *  (DEG F)   *   (DEG)     *   (KNT) 
16-JAN-2010 Smry  *0.26(0.38) *0.27(0.65)  *-0.3( 0.6)  *-0.7(19.  * 5.6(1.22)
 
Note that times are in UTC. The values displayed are  'Observed (error)'
The error value is 'analysis - observed'. I.e. if your observed value is higher
than the computed value, then the error will be negative. You have to pick out
the reading that is in error. The row with the time of 'Smry' is a daily summary
and the data is  'mean(standard deviation)' for each observation during that
day.
 
Graphs: http://weather.gladstonefamily.net/qchart/D4210?date=20100117

[Mark / Ohio]

Looking at your CWOP information page I would say the trees around you are probably breaking up the wind some and your readings are fine.  Your other readings look fine as well.

http://weather.gladstonefamily.net/site/D4210

It's impossible for CWOP to figure your individual micro climate variances into their calculations.  I think they do best on barometer and do monitor to keep my pressure readings in line with their expected during calm weather periods with steady pressure.  But when it comes to temperature, humidity, and wind their accuracy goes down hill fast.  I personally think of the quality numbers mainly as a tool for diagnosing sensors going bad rather then as a calibration tool.  In other words I follow whether the errors are increasing over time or suddenly show a large increase.  That could indicate a problem on your end.  But one also has to be careful there as well because another station in the local area could be messing up the numbers they are generating.

[prkguy]

Here is latest qc report that was in my mail box this morning.    It appears this one is a summary for the week.   Im guessing I received it because again my wind speed is off but it appears that my wind direction is off as well.

Im still confused as to what the numbers in parenthesis represent. 

I checked the anemometer arm and it is pointed at the magnetic north.    To get to true north I need to move it almost 7 degrees to the right or east (if I have my bearings correct for Michigan declination).   I will fix that this week.   Mike



DATE            UTC    *   ALT        * POT TEMP  *  DEW PNT    *    DD        *    FF   
                             *   (MB)      *  (DEG F)    *  (DEG F)      *  (DEG)       *   (KNT) 
17-JAN-2010 Week   * 0.3(0.44)  *0.42(1.13)   *-0.1(0.82)    * 2.1(38.   *3.74(2.09)
 
Note that times are in UTC. The values displayed are  'Observed (error)'
The error value is 'analysis - observed'. I.e. if your observed value is higher
than the computed value, then the error will be negative. You have to pick out
the reading that is in error. The row with the time of 'Smry' is a daily summary
and the data is  'mean(standard deviation)' for each observation during that
day.
The 'Week' row is the summary for the preceding 7 days.
 
Graphs: http://weather.gladstonefamily.net/qchart/D4210?date=20100118

[Bearcage]

Mike,
  I just looked at your arial photo and there are quite a few trees to your south and west.Is your anemometer above the treeline.That may dampen the winds a bit.It also looks like MADIS has been qcing your data for a week.I would think you would need a months worth of qc to do an analysis.It would be nice if you had a prolonged northeast wind to compare to the QC(No trees).Does WxLink send the 2 minute avg or 5 min avg wind to CWOP.It should be 2 min avg with 10 min gust.

                                                    GB

[prkguy]

GB the anemometer is located about 600ft east of the location on the map.   http://weather.gladstonefamily.net/site/D4210

It is on top of the building.  The reason it there is because there are fewer trees to contend with.    The ISS is located at the spot indicated on the map.   I placed photos on Flickr but they have not placed the photos on the CWOP site yet.  But they are visible on Flickr if you go to the CWOP group and use my station ID DW4210.

The trees that I have here are big mature cottonwoods that are 50' high so they do block a lot of wind.

It looks like tonights qc were all good again except for the wind.   http://weather.gladstonefamily.net/cgi-bin/wxqual.pl?site=D4210

Im embarrased to have to ask this but in regards to the 2 minute average is that something I need to set up in my weatherlink settings on my console?     Mike

[Mark / Ohio]

....Im embarrased to have to ask this but in regards to the 2 minute average is that something I need to set up in my weatherlink settings on my console?     Mike

No need to be embarrassed as that is a good question.  Originally I believe it sent only a 10 minute average.  But I'm thinking they changed it around ver 5.7xx adding the additional available averages provided the realtime window is open.  This is in the 5.8.3 help file:

Wind speed (MPH). (The Vantage Pro and Vantage Pro2 systems send 10 minute average wind speed, if you do not have a real-time window open. Monitor and Wizard stations send the current speed. With a real-time window open, i.e. Bulletin [excluding the Strip Chart window], the APRS Data field contains a  two-minute average depending on the selected reporting standard selected in the APRS Setup dialog box.)