New evidence to solve the mystery of the 'eclipse wind'

Mar 15, 2012

(PhysOrg.com) -- Solar eclipses are not only amazing celestial spectacles - they also cause subtle changes to the weather here on Planet Earth, according to meteorologists.

Scientists at the University of Reading have found new evidence that the last full to pass across the UK caused changes to the wind speed and direction, giving credence to the mysterious 'eclipse wind' reported anecdotally by some eclipse watchers.

Thousands of people flocked to Devon and Cornwall - the 'zone of totality' in the UK -  for the eclipse on 11 August 1999, while millions more across the country witnessed a near-total eclipse.

But while the view in the South West was obscured by cloud cover, some onlookers reported feeling an eerie change of wind direction as the sun was temporarily blotted out, in a giant natural atmospheric experiment.

Researchers in the Department of Meteorology at the University of Reading, Dr Suzanne Gray, Senior Lecturer in Systems, and Professor Giles Harrison, Professor of Atmospheric Physics, made use of recent advances in computer modelling power, combined with detailed meteorological measurements from across the UK on the day of the eclipse, to see how the moon's shadow changed the UK weather pattern.

"Although eclipses are known to cause temperature changes, any wind effects have been less clear," Dr Gray said. "This new approach demonstrates regional and direction changes within the southern UK, which may explain anecdotal reports of a mysterious 'eclipse wind'."

Professor Harrison said: "We've been able to demonstrate that subtle changes in the winds really did occur in 1999 associated with the post-eclipse cooling. Our new approach works by comparing the latest high definition weather model predictions for the same day without an eclipse with the observations actually obtained at many UK measurement sites."

The pair's findings, which are published this week in the journal Proceedings of the Royal Society A, add new information to an earlier analysis published by Professor Harrison in 2002. The previous work only made measurements at two sites, whereas the latest results make full use of data from 121 sites across the UK. This extra data, compared with output from new, powerful super-computers running a complex weather forecast model, has given a much clearer regional picture of how the eclipse affected the weather on the day. Weather predictions have become more sophisticated during the past decade, helping weather forecasts to become more accurate, the researchers said.

"This level of model detail was just not available in 1999, and reflects the subsequent major advances made in weather forecasting since then," Professor Harrison said.

Dr Gray added: "Importantly, the detection of the eclipse wind from such a fine scale comparison adds to our confidence in the accuracy of the latest weather forecast models."

A total like that of 1999 will not be repeated in mainland Britain until 2090.

Explore further: For the first time scientists map elevation changes of Greenlandic and Antarctic glaciers

More information: The researchers' paper, S. L. Gray and R. G. Harrison (2012), 'Diagnosing eclipse-induced wind changes', is published online in Proceedings of the Royal Society A.

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tadchem
not rated yet Mar 15, 2012
Itr seems like the 'eclipse wind' may be related to the wind changes that occur on the ground around isolated cumulus clouds. This is especially noticeable on the plains, when summer cumulus clouds are just beginning to develop into cumulonimbus. The differential heating between the sunlit and shaded portions of the terrain produces temperature gradients that become pressure and airflow gradients. This is entirely distinct from the more powerful downburst winds that occur when the precipitation begins.
jwalkeriii
1 / 5 (1) Mar 15, 2012
Dark cloud floats overhead on bright day, temperature changes then wind changes. What's the mystery?
GSwift7
3 / 5 (2) Mar 15, 2012
Itr seems like the 'eclipse wind' may be related to the wind changes that occur on the ground around isolated cumulus clouds. This is especially noticeable on the plains, when summer cumulus clouds are just beginning to develop into cumulonimbus.


Kinda, sorta, but actually in the opposite direction and reverse order of cause and effect. The eclipse should cool the air causing it to compress, drawing nearby air towards it and then down the center of the air column. The cumulonimbus clouds start due to warm air rising in a column, while cool air next to it will be forced down and towards the center. In the eclipse, the cool central column is the effect, and in the storm cloud, the warm central column is the cause.
Callippo
1 / 5 (8) Mar 15, 2012
In dense aether model the analogy of eclipse wind occurs even outside of atmosphere of Earth with neutrinos and another constituents of dark matter, surrounding the massive bodies. At the situation when such object appears at the line, their mutual shielding effect multiply, which leads into huge flow of neutrinos into formed gravitational shadow from outside. It leads to the gravitational anomaly called the Alais effect, between many others. These effects can be studied experimentally for example with monitoring of CMBR noise and neutrino flux intensity during eclipse and with measurements of speed of light, gravitational constant and structure constant during eclipses. The neutrinos should affect the speed of decay of radioactive elements, which should be observable during eclipse as well.
Myno
5 / 5 (2) Mar 15, 2012
I witnessed a form of this phenomenon as an aftermath of the Hawai'i total eclipse (July 11, 1991). Totality passed directly over the Big Island, with the path centered on the town of Keauhou, just south of Kailua-Kona. At that interface between ocean and island, the land is quite steep. The cooling (and sinking) air along the eclipse path likely caused twin horizontal vortexes, which interacted with the steep slope to result in a single vertical vortex, manifested as a waterspout just offshore, followed by torrential local rain in the thunderhead it punched into the upper atmosphere. I stopped my car by the side of the road down into Keauhou and my passengers and I watched the waterspout for the few minutes it remained, before it disappeared into the following downpour.
Paul_Duncan
5 / 5 (2) Mar 16, 2012
Dark cloud floats overhead on bright day, temperature changes then wind changes. What's the mystery?


Okay, now explain why this happens. All you've done is simplify the question.
Benni
1 / 5 (1) Mar 17, 2012
.....actually the real question of this climate change is:"How do we fix this?"
antialias_physorg
not rated yet Mar 17, 2012
.....actually the real question of this climate change is:"How do we fix this?"

Blow up the sun...it's the only way to be sure.