1 Mar 2013

Potten End Newsletter Article 9

This article originally appeared in the Potten End Newsletter, March 2013.

Potten End Weather

“Sunshine is delicious, rain is refreshing, wind braces us up, snow is exhilarating;
there is really no such thing as bad weather, only different kinds of good weather.”

― John Ruskin

The sun seems to have been particularly absent this winter. If we go through our records and add up the number of days where the temperature has been at or below 0ºC (an arbitrary but useful measure of a cold winter) then we find that, as this article goes to press, this winter (Dec 2012 to Feb 2013) is the fourth coldest. The top five coldest winters on our records are:
  1. 2008/09:  47 days at or below 0°C
  2. 2009/10:   45
  3. 2010/11:    39
  4. 2012/13:    38 (incomplete at time of writing)
  5. 2011/12:    28
The remaining years on record average out at about 20 days below 0°C.

Solar Cycles and Their Effect on the Winter

The sun goes through regular cycles of activity in which sun spots, solar radiation and many other factors vary dramatically. These solar cycles have a duration of around 11 years and have been observed for hundreds of years.

Solar cycles were discovered in 1755 and we are now in cycle 24 which started in March 2012.
Recent research for the Met Office by Imperial College London and the University of Oxford suggests that the variability of ultraviolet radiation from the sun over the solar cycle may have a much larger effect on our climate than previously thought.

When the UV levels are low, unusually cold air forms high up over the tropics and is balanced by a more easterly flow of air over the mid-latitudes. This is a pattern that brings easterly winds and cold weather to northern Europe.

The opposite occurs when UV levels are high and westerly winds bring warmer air and milder winters.

Measurements of solar activity indicate that the minimum occurred around December 2008.

No coincidence then that this was the coldest winter we have recorded in Potten End.

This research won’t help with short term forecasts (measured in a small number of days) but it will probably help the Met Office improve seasonal forecasts for months and even years ahead.

The effect of the solar cycles should not be blamed on general global warming. Joanna Haigh, Professor of Atmospheric Physics at Imperial College London, says:

Compared with the effect of man-made emissions over the last century, solar variations still have a very minor effect on long-term global climate trends, but this study shows they may have a detectable influence on winter climate.

March Averages

It is said that March comes in like a lion but goes out like a lamb. These are March’s averages over the first and last week for all years on our records:
  • Temperature: starts at 3.3ºC, ends at 8.2ºC.
  • Daily rain: starts at 1.5mm, ends at 1.3mm.
  • Peak rain rate: starts at 0.5mm/hr, ends at 2.9mm/hr.
  • Wind gust: starts at 11.1mph, ends at 12.8mph.
Temperature and daily rain concur with the saying, peak rain rate and wind gusts would differ. Feel free to interpret them individually or all together at your leisure!

Hope you all have a great spring in spite of or because of the weather!