Calibration Issues? wmr88

[starman316]

I have a OS WMR88

And I am convinced the reported wind speeds on the station are lower than the actual wind speed.
comparing values with a nearby station, the nearby station would report 40mph wind speed and 33.5 speed average and mine would be like 20mph speed 15mph average! hmmm

I tried using the wiki to add a 1.04 for 8 metres and left wind gust at 1.000 but it does not add a higher value to the wind speeds

so far to match I have it set to 1.75 on both speed and gust calibration, then it will double both the values! which seems more realistic

but i would of thought adding wind speed multiplier and leaving wind gust to its default would of doubled speed ie station saying 10mph and cumulus 20mph but it doesnt alter it at all
the only way i can alter speeds in cumulus is adding both wind speed and multiplier

can someone point me in the right direction please?

my anometer is about 2 meters above my roof gutter on a normal 3 bed semi detached house.

perhaps I got the height wrong maybe? or not doing it right within calibration

1.04 for 8 meters and 1.000 (default) for gust

cumulus reports same speed as station even with multiplier added above

cheers

Lee

[steve]

What settings do you have for 'calculate 10-min wind average' and 'use speed for avg calculation'?

[starman316]

calculate 10min average wind is ticked and use speed for average calculation is unticked steve

thanks for the quick response

link pic below showing my speeds compared to another station 1 and a half mile away

https://www.dropbox.com/s/d8b0dcx59p8x0 ... ompare.jpg

[steve]

With those settings, Cumulus is calculating the average and using the (uncalibrated) 'gust' values from your station in the calculation, and applying the 'wind speed' multiplier to the result of the calculation. It's hard to see how it could not be applying the multiplier, it's the same code regardless of station type.

[starman316]

Thanks Steve,

All I want to do is match the wind speed to a more realistic value, as reported with a nearby station as I said I am convinced its reporting lower, could there be a reason for this?

the station is now showing 15.8mph speed yet other station reporting between 40-50mph wind speeds, something is not right, so I am trying to get cumulus to compensate ie multiply the wind speed

but when i do this, it will not multiply by just adding a multiplier to the speed, i have to add the same multiplier to the gust to get cumulus to see a more realistic speed to match the nearby station

I really do not understand how it works or how to fix.

i would of thought just adding the 1.04 to the speed multiply it would add the multiply, but cumulus still shows the same speed as the station after adding the value!! hmmm

[steve]

There can be many reasons why your recorded wind speed is lower than a station less than two miles away; the location, exposure, the siting of the anemometers, etc.

Using a wind speed multiplier of 1.04 when your wind speed is around 15 mph isn't making very much difference to your wind speed at all - less than 1 mph. If you really want to get your speeds in Cumulus close to the ones at that station, you need a multiplier approaching 3.

As you have Cumulus calculating the average speed from the gust values, you can't make direct comparisons of the speed in Cumulus and the speed on the console, they are being calculated in completely different ways. If you want proof that the multiplier is actually being applied, then turn off the 'calculate...' setting in Cumulus and apply a multiplier of 2. Then you should see that the average speed in Cumulus is double that on the console. Make sure you look at the average on the console and not the gust.

[starman316]

Thank You again Steve, I shall have a play, and post my results

[starman316]

ok right if i go to calibration settings, baring in mind i have unticked "calculate" in station settings.

I set wind speed multiplier to 2.000
and leave wind gust multiplier to 1.000

the actual speed still shows the same as the station on the dial

but shows multiplier in Average

if i then change the multipliers like this

speed 2.000
gust 2.000

it then shows double on the dial ie if station shows 20mph dial shows 40mph which is more realistic

am a bit puzzled as to why i have to play with the gust multiplier value to make the wind speed double on the dial hmmmm, would of been better to just adjust wind speed to show on dial but leave the gust as default

shall keep an eye on it now and see if it is not OTT

[AllyCat]

Hi Lee,

my anometer is about 2 meters above my roof gutter on a normal 3 bed semi detached house.

The "correct" (ideal) height for an anemometer is 8 - 10 metres above an "open field" (imagine an airfield), which is of course impractical for most amateur stations. But it seems that yours is not even as high as the ridge of your roof? As an absolute minimum, the anemometer needs to be higher than any nearby obstructions (e.g. by 1/10 of the distance to the obstruction), or the calibration factor will be dependent on wind direction.

AFAIK the multipliers for wind speed and gust are independent values (because most/all stations report them as independent values), so if you set a wind multipler much greater than the gust muliplier then you could/would get (average) windspeeds higher than the gusts!

Cheers, Alan.

[starman316]

thanks Alleycat, yes my anemometer could do with a slight height adjustment so it clears the top ridge, the bracket is on my south facing wall, so I thought today being a southerly would of been ideal to calibrate.
it is not far off the ridge, the bracket is just below the gutter as high as it can go, and the pole is about 6-8 foot, anemometer sits on top of that

I am waiting on delivery of a longer pole

here is picture (top anemometer) no houses to my east, south, north,
houses to my west

I cannot even move it to the side of the house, as i have no eaves it a sloping roof

Ideally I could of done with chimney mounting it, but was concerned about battery replacement, at least being on a pole it is easily changed/maintained

https://www.dropbox.com/s/hkhkcnngbytew ... .57.30.jpg

i'll wait for daylight and take a pic of my surroundings and maybe you guys can point me in the right direction to set this up properly if you woudn't mind, first the longer pole would help!

and I now starting to understand what u mean by the below statement

the multipliers for wind and gust are independent (because most/all stations report them as independent values), so if you set a wind multipler much greater than the gust muliplier then you could/would get (average) windspeeds higher than the gusts!

thanks guys

[steve]

I set wind speed multiplier to 2.000
and leave wind gust multiplier to 1.000

the actual speed still shows the same as the station on the dial

but shows multiplier in Average

Yes, that's how it works. The 'speed' multiplier affects the average. It's the average which is the wind speed. I'm not sure what you mean by 'actual value', but I'm guessing you mean the (station) gust figure.

[mcrossley]

Lee, if you haven't already I suggest you read this FAQ about how to wind speeds in Cumulus and Fine Offsets relate to each other:
http://wiki.sandaysoft.com/a/FAQ#What_d ... tations.3F

[bus_ter]

Just seen this thread. If you see mine I have come to the same independent conclusion regarding wind speeds with the WMR88, that is to use a multiplier of *2 for both wind and gusts to get values that are in the ballpark of surrounding stations. I also had to calibrate for other measurements too. The details are in my thread.

[mildmuck]

I have the WMR88, I use a 35-40 foot pole from the ground*. It is rather long as you can imagine and fun to take down.

I use a 1.600 Calibration in Cumulus, my readings seem to be roughly keeping in with other weather stations in my area, however ... as another member mentioned calibration gets a little tricky when you start taking different wind directions into account.

Roof mount option ?? ....yes better readings. Me climbing on a moss covered roof ? .. not in a million years. Isn't worth the hassle or the risk.

[starman316]

I am still having issue's probably me being thick!

last night we had some strong winds locally,

I was monitoring another local station (davis pro) 1mile from my home) and average was around 30mph, my station was averaging 17mph ??

so I adjusted calibration to roughly match that of the local station (wind speed) average only to find a 93.3mph gust was reported at 4am! and no way is that right

I presume it is because I have set multiplier wind to 2.000 and gust to 2.000

if I leave the wind speed multiplier at 2.000 and change gust multiplier back to 1.000 i find my cumulus wind speed dial matches the one on my station, but I am almost sure the consoles wind speed is reporting low, probably because it is not quite above roof level

but we also had southerly winds again, my anemometer is full view south

my question, is the wmr88 wind speed normally about right?

I think it maybe because it only has a 58sec update so maybe reading lower speeds (when speed outside is low) and maybe not capturing the highest??


ok here is some console readings from 9pm last night, (other local stations and bbc weather saying 29mph average)

my console over 10mins

in mph

10.3
14.8
8.7
7.8
9.8
12.8
9.4
14.1
8.7
11.9
10.5
16.1

other stations were averaging 29mph and gusts of 40mph

none of those match near the reported local stations speeds last night
hence why i need to use the multiplier

where am i going wrong??
it would help if I give the anemometer more height but would this achieve more realistic wind speeds ? considering we had southerly winds last night, the anemometer is on the south side of the roof

what I would like to know, is when i add a multiplier to "just the wind speed" in cumulus why it does not add this multiplier to show on the wind speed dials??

but does when you adjust the gust multiplier too? only i seem to think that then it gives unrealistic gusts (93.3mph) at 4 this morning....

hmmmm ;-( help

edit, steve you said the multiplier affects average (bottom left in cumulus) right ok i'm with you now on that one

but this still does not adjust the wind speed shown on right dials?? unless i add a multiplier to the gust too, then i end up with alse gust readings as i said above

I am almost sure I am to blame and not quite understanding how it works

it just seems when i add 2.000 to both values in multiplier all appears more accurately then i get insane gust speeds hehehehe