WEATHER LORE

SUNSHINE

In the summer many of us jet off southwards in search of the sun. Seduced by the holiday brochures that quote how many hours of sunshine a day or each year we can expect, sun lovers are convinced that south means more.

Measuring the sun isn’t as easy as it appears.

The hours of sunlight each day depend on several factors. Latitude, time of year, which dictates the time of sunrise and sunset and the general cloudiness of the weather all affect how many hours of sunlight a place receives each day or each year on average.

A Campbell Stokes sunshine recorder measures the hours of sunshine. A glass sphere concentrates the suns rays onto a card of heat sensitive paper graduated in hours and a scorch mark is traced across the paper to record the hours of sunshine. It’s not necessary for the instrument to move as the sun conveniently does the moving itself!

But what about areas where the intensity of the sunlight is so low that no scorch mark is recorded. Or holiday resorts that place their recorder on top of the highest building to record every second of the sun from when it first creeps above the horizon to the last rays of the setting sun...and then brag about how sunny they are!

In Britain Blackpool claims 1527 hours a year on average and Hastings on the south coast an impressive 1730 hours.

But even these sites pale into insignificance alongside Los Angeles on the west coast of the USA with 3217 hours or Phoenix in Arizona with an amazing 3752 hours each year.

In the northern hemisphere the longest day is June 21st, the Summer Solstice, and we might expect that month to deliver the most sunshine. In Britain, however, July and August are usually sunnier. Hastings holds the British monthly record receiving 384 hours of sunshine in July 1911.

But spare a thought for the residents of London in December 1890, where at Westminster absolutely no sunshine was recorded at all! This was probably caused by the dust and smoke of the coal burning industries of the day, like the ‘great smog’ of 1952

So, not as simple at it seems then!

And, wait a minute, what about the Land of the Midnight Sun?