Barnes-Botany.co.uk

Welcome to my weather pages!

Circumzenithal arc

The image above shows an unusual optical phenomenon known as a circumzenithal arc or CZA. Associated with high ice clouds like the cirrus show here, it results from refraction within horizontally aligned ice crystals. This example, photographed on 26th October 2011 at my home , was about 65 degrees above the horizon, and shows a vivid segment of what has been described by Gavin Pretor-Pinney as 'a smile in the sky'. Gavin set up the Cloud Appreciation Society, whose website includes a gallery of fine cloud and sky photographs. A detailed explanation of this and other optical phenomena can be found at the Atmospheric Optics website.

This part of mid-Wales is sparsely populated and local weather records are correspondingly sparse.

Setting the scene

Setting the scene

Alltgoch lies in hilly country, with higher land to the north, east and west, and a clear view down the valley of the small Afon Aeron, which flows between steep, wooded banks about 20m lower than the house. The view above is from the hillside across the river, looking up-stream. The house has an Ordnance Survey benchmark indicating its altitude as 137m. As so often in hill country, the weather can vary dramatically within a very small distance, and you should bear this in mind when using these figures.

My weather station is definitely not of a professional standard, but uses either good quality 'amateur' instruments or home-made ones. In January 2004, I replaced most of my old set-up with a electronic system.

The weather day runs 0900 GMT and current station records are uploaded automatically to the following sites:

Location: north of the village of Llangeitho, Ceredigion,
at 52.24 deg. N., 4.01 deg. W.