Geographical Variationin the Wind Resource
Long-term Wind speed Variations

There is evidence that the wind speed at any particular location may be subject to very slow long-term variations. Although the availability of accurate historical records is a limitation, careful analysis by, for example, Palutikoff, Guo and Halliday (1991) has demonstrated clear trends. Clearly these may be linked to longterm temperature variations for which there is ample historical evidence. There is also much debate at present about the likely effects of global warming, caused by human activity, on climate, and this will undoubtedly affect wind climates in the coming decades.

Apart from these long-term trends there may be considerable changes in windiness at a given location from one year to the next. These changes have many causes.
They may be coupled to global climate phenomema such as el nino, changes in atmospheric particulates resulting from volcanic eruptions, and sunspot activity, to name a few. These changes add significantly to the uncertainty in predicting the energy output of a wind farm at a particular location during its projected lifetime.