CRUTEM4 sites and the placement of Stevenson screens

I am surprised that some of the UK climate records used by the Met Office to calculate their global land temperatures for CRUTEM4 with, are from sites where the instrument enclosure, primarily the Stevenson screen, has been compromised over the years by the encroachment of buildings, car parks, and runways and the various ‘climate’ sites around the country, to such an extent that it must in some way be affecting the temperature sensors. Creeping urbanisation has been happening for years, and is not a new problem, it’s a bit like how politicians suddenly realised that life expectancy has been on the rise for the last 100 years.

Before I go any further these concerns have been voiced before, and a review of the observing sites of the UK has been done before, and much more thoroughly than I can do in this short article, most notably in the Surface Stations Survey by Tim Channon on the TallBloke blog.

The Surface Stations Survey work was done a few years ago now, and as far as I see wasn’t directly linked to the ‘raw’ monthly CRUTEM4 temperature data that you can freely download from the Met Office, and which is used to calculate a monthly estimate of global land temperature with. In recent years the Met Office, for some reason known only to themselves, have reduced the number of the UK sites from well over 100 twenty years ago (fig 1), to just 18 sites in 2017 (fig 2).

Figure 1 – CRUTEM4 Sites 2000

Figure 2 – CRUTEM4 Sites 2017

Here’s a graph (fig 3) of how the total number of UK sites that are currently used in the CRUTEM4 calculations has declined in recent years.

Figure 3 – WMO Block #03 sites

The irony of this 80% or more reduction in UK sites used, is that two of the three sites used to calculate the composite CET series, the longest instrumental record of temperature in the world, are now no longer used – Rothamsted (1872-2012) and Preston Moor Park (aka Stonyhurst 1960-2012).


Poor siting of instrument enclosures

But I digress, what I really wanted to moan about bring to people’s attention was the precarious siting of the Stevenson Screen at some of the 18 sites that we still use to calculate a global temperature with. Generally the siting of the screen didn’t look too bad, but there are a number that are poor, and here are three of the worst sited Stevenson screens that I found using Google Maps. Of course guessing where the screen is an art that has become a bit of an obsession with me. The biggest offenders are all at airports, namely Aberdeen, Valley and the infamous Heathrow (figs 4, 5 & 6).

Figure 4 – Courtesy of Google Maps

Figure 5 – Courtesy of Google Maps

Figure 6 – Courtesy of Google Maps

At this point I would like to say I wouldn’t be able to do this without Google maps, but I have noticed that the generally the quality of the highest zoomed images is inferior to those in the Google map images of the Surface Stations Survey. This might be just a Google maps issue, or it maybe a deliberate restriction on quality and zoom level requested by the MOD for RAF stations. The yellow circle is at a radius of 10 metres and the blue circle at a radius of 30 metres. I won’t go into detail of what I estimate the WMO classification for each site would be as regards temperature, I’ll just leave it your imagination.

What can the Met Office do about it?

When I was an observer every so often at an outstation, someone would come round and inspect the ‘met’ enclosure to see if it was being maintained correctly, I wish now that I had taken a keener interest in what the inspector was looking at other than if the bare patch had been weeded recently! I wonder if there was tick box to confirm that no jet engines were being run up within 30 metres of the screen? I can remember quite clearly being wafted by warm gusts of air from an F3 Lightning at Binbrook en route to the Stevenson screen across the pan to do the 09 UTC observation even in the middle of winter.

They could if they wanted to without much effort do the following with the climate records used from the UK in CRUTEM4:

  • Reinstate the best of the climate stations that have been lost in recent years, but not the records from RAF Waddington or RAF Brize Norton please!
  • Immediately reinstate the temperature climate records for Rothamsted and Stonyhurst, at the same time adding the one from Pershore, so that the three stations used for the renown CET series are included in the calculations, which to my mind would be only fitting!
  • Remove Heathrow until the enclosure has been relocated possibly in the middle of Bushy Park!

This would be very easy for the Met Office to do, they wouldn’t have to go cap in hand to any other meteorological service to ask them to supply the data, as they already have those temperature records.

I know just how sensitive temperature sensors are in AWS these days, I have a Vantage Pro, and over the years I’ve relocated it a number of times in our garden, each location had its different weaknesses, too close to trees or the hedge, or too close to an area of paving, now it’s far too close to the garage. It certainly is a very difficult, if not impossible task to find a location on a modern airfield that’s totally unaffected by external influences on temperature. But in this day and age of advanced wireless communication, I just can’t believe it’s not possible to install AWS as far away as possible from any runway, car park, building or road, at any site, which invariably is at an airport, be it military or civilian. I’ve been doing it with my AWS without a problem for the last 13 years, albeit at a range of less than 10 metres! Inevitably this will have to be done as the demand for green space on airfield sites increases till the whole damn place is paved for a parking lot.

Advertisements

About xmetman

I am an exmetman who is passionate about all things to do with weather and climate. I have no axe to grind, and am continually upsetting people on both sides of the global warming debate with the articles that I publish, hell, I'm even banned from commenting on the Met Office's own blog! What I do fight for is the freeing up of climate, observational and forecast data collected and created on our behalf by the Meteorological Office.
This entry was posted in Central England Temperatures, Global Surface Temperature, Met Office, Weather Stations. Bookmark the permalink.

One Response to CRUTEM4 sites and the placement of Stevenson screens

  1. wansteadmeteo says:

    I still haven’t had an answer from the Met Office about the high max in June. Ogimet state that it was 33.9C while Met Office state it was 34.5C. Are there two enclosures at Heathrow? It is a simple question.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s