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Droughts in the UK |
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Different parts of the world have different climates, so each country has its own definition of a drought.
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A drought in the UK used to be defined as 15 consecutive days with less than 0.25mm rain on any one day, but this regimented definition was abandoned in the mid-80's after running into problems. Different organisations couldn't decide whether the drought had ended or not, so it seemed easier if each made their own definitions. It is far more sensible to judge each drought on its own merits...
Not many people mourned for the end of the strict definition, as it was always coming under scrutiny. If after 20 days there is 0.26mm rain, is the drought officially over? If there is less than 0.25mm rain for 30 days is that 2 droughts? It is far more sensible to judge each drought on its own merits and even then it is always hard to determine whether a drought has ended. Hindsight as always is a wonderful thing.
In a country affected by a succession of weather fronts it is sometimes hard to imagine how Britain could ever be affected by droughts, but high pressures do affect us too. In between our fronts are ridges of high pressure. These are generally short lived, but sometimes a large area of high pressure called a 'blocking high' can dominate our weather for up to a month. As their names suggests these 'block' other weather and force fronts to skirt around them. ...high pressures can cause long dry spells, and eventually droughts.
These high pressures can cause long dry spells, and eventually droughts. This is what caused the drought in 1976, when a blocking high dominated our weather for much of the summer. The drought of the mid - 80's on the other hand dragged on for years as the winter rain was not sufficient to replenish the ground water supplies.
Exactly how frequent droughts are in the UK is hard to pinpoint. 1976 was definitely a drought, as were the mid 80's. There was also one in the mid 90's, but different companies may well have other periods that they would also like to include in that list. The trend since the 1860's is for wetter winter and drier Summers, this trend has been accentuated since the 70's. This seasonal cycle is strongest in the south and east of the country and if this trend continues then we can certainly expect more droughts in the future. | |||||
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