Reigate: some effects of the eclipse on our local weather

March 21, 2015 — 1 Comment

eclipse shadow

eclipse shadow

Sadly in Reigate and across the SE of England a blanket of thick cloud persisted throughout the eclipse period and we had no direct view of the amazing spectacle. Elsewhere in the UK views were mostly better, so we had about the worst possible situation: thick stratus and stratocumulus that stubbornly didn’t move until midday.  Nevertheless, effects of the eclipse were recorded and experienced. The afternoon was cloudless blue sky, so the weather played with us.  On the bright side, our student weather club eclipse forecast turned out spot on here! NewEx RESULTS: scroll down

cloudy in the SE

cloudy in the SE

Darkening skies: eyes adjusted to the fading daylight but the timelapse below shows the light fading as the camera exposure and shutter speed were taken off auto and set to manual. Spot the lights automatically coming on.

Cooling down: as solar radiation faded, temperatures locally fell a little but only by less than 0.5C or so.  As the eclipse was relatively early in the morning it seems that the usual climb in temperature was somewhat held back by the eclipse cooling.  Dew point, rather surprisingly, also dipped somewhat showing a somewhat drier atmosphere for a short period during the eclipse.

2015-03-20_21-20-06

Pressure change? Although we cannot directly experience this, pressure fell markedly towards the end of the eclipse period.  The overall forecast for the day was for pressure to fall… but was the pressure “held up” somewhat by cooling subsiding air from aloft?  Well, we won’t know for sure but the pronounced “pressure cliff” seems to nicely coincide with the maximum of the eclipse period.  The wind moderated somewhat through the eclipse which can been seen by the slight lowering of max wind gust speeds below.  Nationally, NewEx found little evidence of the “eclipse wind” (see below).

2015-03-20_21-28-25

Overall, the eclipse in the South East and for us in Reigate was spoilt by cloud and we didn’t get to see this rare event.  Nevertheless, there is some good meteorology that will come out of this, not least to investigate the influence of solar radiation on weather models.

another eclipse shadow

another eclipse shadow

National Eclipse Weather Experiment: summary of findings quoted from University of Reading Meteorology Department “StarGazing Team”.

“After the data had been uploaded, we collected together the observations from the different sites and averaged them. From combining the measurements from all the participants, these show a clear drop in temperature across the country.

Temperature

Temperature change

A reduction in cloud in central England during the eclipse is also apparent. This is a very interesting result for further analysis, and one which would be hard to obtain other than through the efforts of a disciplined group of distributed human observers such as yourselves.

2015-03-24_18-09-58

cloud cover change

This finding is therefore almost certainly unique to NEWEx. As you may have noticed, winds were mostly light across the country during the eclipse, which meant the circumstances were not well suited for detecting changes in the wind. The so-called “eclipse wind” unfortunately remains elusive, so more work will be needed on this.”

2015-03-24_18-11-02

wind change

more here from NewEx http://www.met.reading.ac.uk/outreach/newex_2015/index.html

Trackbacks and Pingbacks:

  1. #Reigate March weather summary « Reigate Grammar School Weather Station - April 7, 2015

    […] March will be remembered for the near total “deep” solar eclipse that crossed much of the UK on 20 March.  Sadly for us in Reigate and much of the SE we saw nothing of it except a gathering gloom and slight dip in temperature.  More on our eclipse observations here: https://rgsweather.com/2015/03/21/reigate-some-eclipse-effects-on-weather/ […]

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