Out & About …

… on the North York Moors, or wherever I happen to be.

A view from a snow-covered Hanging Stone over a temperature conversion covering the town of Guisborough.

A day of strange atmospherics

On this day in 2005, at 0601 in the morning, a huge explosion rocked an oil depot in Buncefield near Hemel Hempstead in Hertfordshire. It was the largest in peacetime Europe and the noise is said to have been heard as far away as the Netherlands1Wikipedia Contributors. 2022. ‘Buncefield Fire’, Wikipedia (Wikimedia Foundation) <https://en.wikipedia.org/wiki/Buncefield_fire#Explosion_and_fire> [accessed 11 December 2022].

I seem to remember people at work saying they had heard the boom here on Teesside but suspect, as this was a day later, there may have been some spin in their re-telling.

That the sound carried such a huge distance was due to there being a temperature inversion present on that Sunday morning.

A temperature inversion creates a ‘sandwich effect’ when a layer of warmer air traps a cooler layer near the surface. Sound, light and radio waves can bounce between the top of the cool lower layer of air and the ground.

The explosion would have created an extreme form of sound, called a shock wave. In 1955, a nuclear weapon test in Russia created a shock wave that bounced back in the inversion layer, knocking over a building 40 miles away killing a young girl2Wikipedia Contributors. 2022. ‘RDS-37’, Wikipedia (Wikimedia Foundation) <https://en.wikipedia.org/wiki/RDS-37#Test_aftermath> [accessed 11 December 2022].

An inversion can also produce an optical illusion such as a mirages or ‘Fata Morgana‘ in which a ship, for instance, appears to float above the horizon.

A mist covered Easby Moor, with a lone runner approcahing the silhouetted Capt. Cook's Monument
A mist covered Capt. Cook’s Monument.

I saw no floating ships this morning as I descended out of the cloud hugging the moor tops.  In brillant sunshine the remains of a temperature inversion hung over Guisborough.

Earlier, Easby Moor, at 324m asl., was not quite high enough to penetrate the cloud layer.


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