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11-02-2021, 01:23   #571
Danno
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The three main components of the Davis can and IMHO should be separated where possible. Also, all sensors should be ~10m away from buildings and artificial surfaces.
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11-02-2021, 01:48   #572
Nqp15hhu
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So if I move it to be freestanding will it remove that? I mean today it was 3c above the actual temp.
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11-02-2021, 07:30   #573
Gaoth Laidir
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So if I move it to be freestanding will it remove that? I mean today it was 3c above the actual temp.
It definitely shouldn't be near the fence.
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19-02-2021, 15:20   #574
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Anyone here set up a wow account?
I've set up the account but how to get my station reporting is far from clear
I mean where is my station ID for example?
It was never emailed to me
I just got a generic thank you for registering
Its simple enough to set up.on the weather display software,you just input that station ID and pin
But where is the station ID ?
Thanks
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19-02-2021, 15:27   #575
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I agree it’s very confusing.
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20-02-2021, 00:30   #576
Danno
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Originally Posted by AuntySnow View Post
Anyone here set up a wow account?
I've set up the account but how to get my station reporting is far from clear
I mean where is my station ID for example?
It was never emailed to me
I just got a generic thank you for registering
Its simple enough to set up.on the weather display software,you just input that station ID and pin
But where is the station ID ?
Thanks
I setup WOW but it was via the UKMO before Met Eireann setup our one. Maybe try signing up there? MetE's WOW page mirrors the UKMO one anyways.
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20-02-2021, 02:46   #577
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So if I move it to be freestanding will it remove that? I mean today it was 3c above the actual temp.
I realise this is from more than a week ago. Is there anything blocking the wind on that day? It was an east or NE wind that day. A wind obstruction can easily account for the 3C rise.
If no wind obstruction then I think something is wrong.

Make sure the fan is operating. With this design of aspirated shield, once the fan stops, there is little natural air flow around the sensor.

I had an aspirated station and changed to a passive shield. Yes on still summer days, it over reads, but by less than 1 degC. Those days are few and I think for the rest of the time, the passive shield is better.
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20-02-2021, 04:08   #578
Nqp15hhu
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I realise this is from more than a week ago. Is there anything blocking the wind on that day? It was an east or NE wind that day. A wind obstruction can easily account for the 3C rise.
If no wind obstruction then I think something is wrong.

Make sure the fan is operating. With this design of aspirated shield, once the fan stops, there is little natural air flow around the sensor.

I had an aspirated station and changed to a passive shield. Yes on still summer days, it over reads, but by less than 1 degC. Those days are few and I think for the rest of the time, the passive shield is better.
Hi, yeah there is a wall or building to the east of the station. Throughout the easterly we mostly had a SE or E wind. The buildings are about 30-40m from the station.

And there are buildings all around my house (aside from the north). Do you think removing it from the fence would make much of a difference re: accuracy?
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20-02-2021, 08:14   #579
Gaoth Laidir
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Hi, yeah there is a wall or building to the east of the station. Throughout the easterly we mostly had a SE or E wind. The buildings are about 30-40m from the station.

And there are buildings all around my house (aside from the north). Do you think removing it from the fence would make much of a difference re: accuracy?
Definitely.
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20-02-2021, 09:40   #580
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Originally Posted by Nqp15hhu View Post
Hi, yeah there is a wall or building to the east of the station. Throughout the easterly we mostly had a SE or E wind. The buildings are about 30-40m from the station.

And there are buildings all around my house (aside from the north). Do you think removing it from the fence would make much of a difference re: accuracy?
The fence creates a micro climate as it provides quite a bit of shelter down wind and in summer sun is a heat absorber that will raise the temperature of the air adjacent. If the station is positioned high enough so the bottom of the shield is higher than the fence, that will negate the issue somewhat. With the shield, the air enters the bottom. This air needs to be from the transient air and not from any micro climate that the fence may be creating.

I do think the walls and buildings can account for the 3c rise. For the vast bulk of us, we don't have a perfect site, so there is compromise to make the best of what we have. Raising the station, even by a foot or 2 may help to get it clear of the fence and reduces the influence of the nearby obstructions.
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20-02-2021, 09:56   #581
Gaoth Laidir
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Quote:
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The fence creates a micro climate as it provides quite a bit of shelter down wind and in summer sun is a heat absorber that will raise the temperature of the air adjacent. If the station is positioned high enough so the bottom of the shield is higher than the fence, that will negate the issue somewhat. With the shield, the air enters the bottom. This air needs to be from the transient air and not from any micro climate that the fence may be creating.

I do think the walls and buildings can account for the 3c rise. For the vast bulk of us, we don't have a perfect site, so there is compromise to make the best of what we have. Raising the station, even by a foot or 2 may help to get it clear of the fence and reduces the influence of the nearby obstructions.
I still think it needs to be away from the fence altogether, on a free-standing pole. On a calm day the heat will rise off the fence and affect the sensor, even if it's a few feet above the fence. That's why I never get why some people put their sensors on the roof, right above a hotplate of tiles, or near a tarmac driveway, etc. Of course, for a personal station that's of no great consequence, but if it's an official synoptic station that feeds the weather models (I'm thinking of you, Shannon) then such errors get transferred into errors in the model output. Garbage in, Garbage out. That's why I have a bee in my bonnet about Shannon.
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21-02-2021, 10:35   #582
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The fence will also cause a wind eddie
Rising the station will rise the temp on frosty nights/days
That could easily be a degree or two in frost

Youll need to have the rain guage bolted onto something solid that wont wave sbout in wind gusts as that will tip the spoon causing over reading of rain
Looking at the wow sites and weatherlink,thats happening a lot especially when you compare met ACS's nearby to personal stations
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21-02-2021, 22:46   #583
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This is the setup of my station. There is grass behind it followed by tarmac. I can’t seem to find a location that has pure grass.

It’s overeading again by about a 1c.

Don't mean to be the bearer of bad news but i see your problem right there. Its the 24hr FARS. This shield is only for the hottest of climates and reacts utterly slow in temp variation in use with the passive shield or the more reliable daytime FARS.

When I use to record climate data for MET.ie, i found this out. Im using Davis AWS for 20 years now with the original VP1 then upgraded to VP2 when that was released, i further upgraded the sensor module included with a newer vp2 4 years ago to the newer version for temp/hum etc.

I had my Davis 24hr FARS in close proximity to the Stevenson screen. The 24hrs FARS responded very slowly to temp variations even though drawing air into the chamber consistently. I concluded the that the inner chamber is too insulated and therefore does not respond well to Ireland's Climate but maybe only for the likes of Death Valley, its accurate.

I had a standalone temp/hum station on one side and 24hrs on the other, the dry bulb in screen and passive shield on the temp/hum station done well at night with passive shield slightly higher in direct sun. The 24hr FARS only slowly reached minimum values but if the temp climbed suddenly during night time, the min on the 24hr was way higher then my max/min in the Stevenson screen and passive shield as it was terrible
to react to sudden change.

I got the daytime FARS, and it was closer to the professional kit supplied by MET.ie than either the 24hrs FARS or the passive shield. The daytime only runs in sunlit days and chamber more exposed to draw in a better air flow.

24hr FARS is good for maybe hollows on the hottest of days here in Ireland.

Plus, what you record is your own environmental conditions, comparing to sites close to you (unless its a faulty sensor and reading way above) its not really accurate either. UHI or urban heat islands and micro climates particularly close to materials that and conductive to heat can play havoc with temp.
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22-02-2021, 10:29   #584
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I wonder are the slow temperature response of the V2 sensor really to do with the 24 hr fars alone? I only have the original daytime fan (which works only in direct sunlight) and the temperature reading is still very slow to respond to relatively sudden changes (which may be down to an issue with the "Sensiron SHT31" model) and particular so in the colder part of the year. For example, a prob thermometer I have hanging out the back window will respond immediately to the smallest and largest of changes, for example such as when a typically cold rain or hail shower passes over, where temp can fall as much as 4 or 5c in a couple of mins, yet the Davis sensor will take many minutes to register such a rapid change (and not register it fully if there is a subsequent rapid rise in temps once the shower has passed) and particularly so with falling temps.

Regarding NQP's set up, he could maybe help his problem a little by painting his fence white as this will help stop it absorbing heat in direct sunlight and emitting back out into his sensor. My own station is located in a suburban back yard (and at a height of over 12ft!!) so temp & humidity readings will naturally not be in alignment with nearby official stations out in the middle of nowhere, but I'm cool with that.

Last edited by Oneiric 3; 22-02-2021 at 10:34.
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22-02-2021, 12:44   #585
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Theres no fan on mine and thinking about it and looking back through stats,temp responses are pretty quick
The unit is very exposed to tge prevailing winds though
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