Grass minimum thermometer

[enka]

Hi, I am not certain if I am in the correct topics page, however, if I am, could someone please tell me the correct time of day to place my Grass min thermometer outside?

Many thanks

Enka.

[fUnKy]

What's a grass minimum thermometer? (am I about to look silly?)

[enka]

Hi fUnKy, Perhaps I should have called it a grass minimum air thermometer. It is a thermometer which records the overnight temperature i.e. ground frost.

enka

[4wd]

Surely if you hope to record the day's minimum it needs to be out all day?

If you wanted to just compare readings at a set time over the year at a set time then 9am or possibly noon (GMT?) would be a reasonable choice.

9am is the traditional start and end of a day's records for the Met Office - when readings were taken manually it was at that time so far as possible.

[The PIT]

I leave mine out all day. Sometimes in summer the heat will put a bubble in it or it's the foxes playing with it. Although if place it so that's sheltered from the main heat of the sun i.e shadow from midday onwards it shouldn't be a problem.

[enka]

I am recording minimum air temperature, which is usualy overnight, I do my obsevations at 0900 GMT, but I believe you should take the thermomter in during the day and put out sometime during the evening.

[enka]

Hi the PIT, I too have been leaving mine out all day, and as you say, the heat does sometimes put a bubble in it. However, I saw somewhere that they should be put out in the evening, the question is, at what time, or does it not matter?

[fUnKy]

Thanks Enka, i thought I was missing out on some special piece of kit.

Mines out all of the time, but in a nice sheltered place. And I have electronic and a more traditional one to check the accuracy every now and again. I sware my back yard must add a degree or so though as I am surrounded by houses pretty much on all sides.

[Terminal Moraine]

Hi the PIT, I too have been leaving mine out all day, and as you say, the heat does sometimes put a bubble in it. However, I saw somewhere that they should be put out in the evening, the question is, at what time, or does it not matter?

1800 g.m.t is the standard time for putting out the grass minimum thermometer, or at the last observation hour before sunset if you're doing regular manual observations.

You can leave the thermometer out all day but if so it needs to be fitted with an anti-condensation shield at the end furthest from the bulb.

I tend to leave my grass min' thermometer out all day from about October through to April but put it in the shade during daytime in the summer. It's possible during winter for the grass min' to occur after 0900, particularly if there's a snow cover, and this would be missed if the thermometer was taken in at 0900. In summer it's very rare for the grass min' to occur between 0900 and 1800 g.m.t.

[The PIT]

The main problem I get is remembering to put it back out or move it back in from the shade. As you say the grass min in winter the lows can occur after nine so in winter it needs leaving out.