One for the techies on here. I have just been informed that grass minimum temperatures are taken 3cm above ground level, the Met Office standard illustrating a thermometer over artificial grass. I'd always thought that the level is 5cm? I am also surprised that artificial grass is used - surely the insulating properties of something that is plastic will give an artificially high figure? And soil / grass radiate heat at a much higher rate than artificial grass?

On Sunday, October 29, 2017 at 9:12:35 PM UTC, Scott W wrote:
One for the techies on here. I have just been informed that grass minimum temperatures are taken 3cm above ground level, the Met Office standard illustrating a thermometer over artificial grass. I'd always thought that the level is 5cm? I am also surprised that artificial grass is used - surely the insulating properties of something that is plastic will give an artificially high figure? And soil / grass radiate heat at a much higher rate than artificial grass?

And the tweet from Liam Dutton https://twitter.com/liamdutton/statu...42862872436737

When mig thermometers were used the regulation height was 2.5cm to 5cm above ground with the thermometer bulb “just touching the tips of the grass�. (Are mig thermometers still used?)
The radiation properties of the grass surface is dictated by the sub soil structure, sandy, clay, dry, wet, etc etc. As far as I’m aware, when artificial grass is installed, a thick layer of sand, then a weed resistant layer then the artificial turf is installed. This obviously makes all installations similar but none representative of the area. I’m sure artificial turf must have been trialed, but because of the sub soil differences in the area I can’t see how there’s any like for like comparison possible.

On Monday, 30 October 2017 18:51:58 UTC, Desperate Dan wrote:
When mig thermometers were used the regulation height was 2.5cm to 5cm above ground with the thermometer bulb “just touching the tips of the grass�. (Are mig thermometers still used?)

mig have been taken out of use at all MetO sites for H&S reasons, however grass min thermometers are alcohol in glass and are still used at manual MetO sites such as Copley.
We have artificial and natural grass here. The artificial normally reads higher.
Ken
Copley
Teesdale

Ken Cook wrote:

On Monday, 30 October 2017 18:51:58 UTC, Desperate Dan wrote:
When mig thermometers were used the regulation height was 2.5cm to 5cm
above ground with the thermometer bulb “just touching the tips of the
grass�. (Are mig thermometers still used?)

mig have been taken out of use at all MetO sites for H&S reasons, however
grass min thermometers are alcohol in glass and are still used at manual MetO
sites such as Copley. We have artificial and natural grass here. The
artificial normally reads higher. Ken Copley
Teesdale

We have natural green grass!

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
Twitter: @TideswellWeathr

"Desperate Dan" wrote in message
...

(Are mig thermometers still used?)

Aren't they 'gallium' in glass now, where 'gallium' or more correctly
'Gallistan' is apparently a eutectic alloy of Gallium with Tin and Indium.
Freezing point is -20C so less useful as a minimum thermometer.

The artificial normally reads higher

Is it consistently higher summer and winter?

On 30/10/2017 19:20, Norman Lynagh wrote:
Ken Cook wrote:

On Monday, 30 October 2017 18:51:58 UTC, Desperate Dan wrote:
When mig thermometers were used the regulation height was 2.5cm to 5cm
above ground with the thermometer bulb “just touching the tips of the
grass�. (Are mig thermometers still used?)

mig have been taken out of use at all MetO sites for H&S reasons, however
grass min thermometers are alcohol in glass and are still used at manual MetO
sites such as Copley. We have artificial and natural grass here. The
artificial normally reads higher. Ken Copley
Teesdale

We have natural green grass!

The problem with natural grass (green or otherwise) is it has a tendency
to grow. And if allowed to grow too much at an unmanned station (or even
a manned one) then the temps won't be any more representative than
artificial grass (which at least doesn't grow). Of course, if the
station's manned there's always someone to cut it. Isn't there?

On Monday, October 30, 2017 at 7:49:01 PM UTC, Metman2012 wrote:
On 30/10/2017 19:20, Norman Lynagh wrote:
Ken Cook wrote:

On Monday, 30 October 2017 18:51:58 UTC, Desperate Dan wrote:
When mig thermometers were used the regulation height was 2.5cm to 5cm
above ground with the thermometer bulb “just touching the tips of the
grass�. (Are mig thermometers still used?)

mig have been taken out of use at all MetO sites for H&S reasons, however
grass min thermometers are alcohol in glass and are still used at manual MetO
sites such as Copley. We have artificial and natural grass here. The
artificial normally reads higher. Ken Copley
Teesdale

We have natural green grass!

The problem with natural grass (green or otherwise) is it has a tendency
to grow. And if allowed to grow too much at an unmanned station (or even
a manned one) then the temps won't be any more representative than
artificial grass (which at least doesn't grow). Of course, if the
station's manned there's always someone to cut it. Isn't there?

I cut mine twice a week with shears - it is a small area and not a laborious task. I suppose if it is not used for long-term record purposes it is not such a big deal - the grass minimum can obviously be used to warn of road ice and other hazards.

On Monday, 30 October 2017 19:30:14 UTC, JohnD wrote:
"Desperate Dan" wrote in message

(Are mig thermometers still used?)

Aren't they 'gallium' in glass now, where 'gallium' or more correctly
'Gallistan' is apparently a eutectic alloy of Gallium with Tin and Indium.
Freezing point is -20C so less useful as a minimum thermometer.

Zeal alcohol (coloured red)in glass for dry and wet bulb, MetO BS692 alcohol in glass (clear) for all minima - screen, concrete, grass - same as always.
Vaisala electronic unit for max.
On radiation nights artificial turf is always higher, winter and summer.
Ken
Copley
Teesdale