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Polar mirage-Novaya Zemlya effect

Baku, March 10, AZERTAC

The Novaya Zemlya effect is a polar mirage caused by high refraction of sunlight between atmospheric thermal layers. The Novaya Zemlya effect will give the impression that the sun is rising earlier than it actually does or the sun is setting later than it actually does, and depending on the meteorological situation, the effect will present the Sun as a line or a series of lines (which is sometimes referred to as the "rectangular sun").

The term originates from January 1597 when a member of Willem Barentsz's polar expedition, which had spent the winter on Novaya Zemlya, an archipelago in the Arctic Ocean, claimed to have seen the Sun appear above the horizon two full weeks prior to its calculated return.

A similar effect was seen in the Antarctic by Ernest Shackleton during his 1914-17 expedition. He saw the sun seven days after it had set below the horizon and, two months later, five days before it reappeared above the horizon.

Under Polar conditions, severe air temperature gradients can exist above the ice surface. When there is a strong temperature inversion layer – colder air below a relatively warmer layer – we have the conditions for a Novaya Zemlya (NZ) mirage. It consists of the trapping of light rays beneath a thermocline of large horizontal extent. The inversion layer must be at least 400 km thick.

Apart from the image of the Sun, the Novaya Zemlya effect can also elevate the image of other objects above the horizon, such as coastlines which are normally invisible due to their distance.

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