Use of Stevenson Screens

For discussion of any observing equipment, from Stevenson Screens and manual instruments to electronic weather stations

Use of Stevenson Screens

Postby Roland Marshall » 2012 Jul 28, 21:37

The "official" weather station at Pearson Park, Hull ceased observations last year. However this manual station has been replaced by two! automatic sites in Hull, one in West Park and another in East Park. The East Park site is the best being better exposed and with grassed enclosure with a Stevenson screen. The West Park site is tarmaced with no Stevenson screen.

Both sites take temperature readings from a Gill radiation screen at a height of approximately 2 metres.

Is this the normal practice at automatic stations when a Stevenson screen is available at the standard 1.25 metres?

Roland
Hull North
2m
Roland Marshall
 
Posts: 37
Joined: 2012 Jan 29, 07:35

Re: Use of Stevenson Screens

Postby Stephen Burt » 2012 Jul 29, 10:39

Roland, you don't say who runs these sites, but your first point of contact ought perhaps to be to check with the site authority. If it is a local authority, they may well have just had an automatic system installed by their supplier to replace an existing manual site, without knowing or specifying the standards that should have been followed.

The Stevenson screen at 1.25 m remains the standard for temperature measurements in the UK and Ireland, although of course many continental sites would use a 2 m exposure. The latter also has some advantages when it comes to protection against vandalism etc, and this may have influenced the siting. There's also the fact that those small Gill screens are about a tenth of the price of the plastic Metspec screens, and I'm sure budget must have come into it somewhere (although I would have thought if a screen was already on the site that would have been the better choice).

To the best of my knowledge, MetO standard climatological sites are still mandated to use a Stevenson screen. The MetO climate sites network map still shows 'Hull West Park' and 'Hull East Park' as current sites, so I'd be surprised if this is perhaps anything other than a temporary measure. I would certainly be concerned if 'official' records were being made from a small AWS screen at 2 m over tarmac.

I'd be interested to know the outcome of your enquiries into the matter, perhaps you can report back in due course?

SB
-----
Stratfield Mortimer, Berkshire - central southern England
51.4°N, 1.0°W, 60 m AMSL, station grade A - AAAA47R
Records commenced here 1987 - local records available back to 1862
The Weather Observer's Handbook: www.measuringtheweather.com
Stephen Burt
 
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Location: Stratfield Mortimer, Berkshire; a well-exposed rural site, 10 km SW of Reading

Re: Use of Stevenson Screens

Postby Roland Marshall » 2012 Jul 30, 11:06

The site authority for these sites is Hull City Council but the equipment is funded by OPAL (Open Air Laboratories Network).They wish to see if there is an urban heat island effect in Hull.

Pearson Park weather observations commenced in 1867 and until recently you were able to obtain a photocopy of the detailed monthly observations for each day including a daily weather diary.

This service is no longer available for recent data . I wished to obtain some data for May 2012 and this is how I found out that the Pearson Park site had ceased observations. The explanation :-We stopped this because the Met Office own the equipment and also any data obtained from this equipment.

I expect only the automatic data will be collected now with no weather diary record continuing.

Roland
Hull North
2m
Roland Marshall
 
Posts: 37
Joined: 2012 Jan 29, 07:35

Re: Use of Stevenson Screens

Postby Roland Marshall » 2012 Jul 31, 11:18

A correction to my original post.

The West Park site in Hull also has a Stevenson screen on the tarmac.

Roland
Hull North
2m
Roland Marshall
 
Posts: 37
Joined: 2012 Jan 29, 07:35


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