Here Comes the Rain - Part 2

It is official. Britain has had the wettest summer since 1912 according to the Meteorological Office. This follows one of the wettest springs on record. Is this evidence of climate change or simply natural variation in the weather?

To try answering this question, data from a weather station near Glasgow has been analysed . The first part of this article presented annual rainfall records and concluded that there has been only a slight increase in annual rainfall over the past decade compared with a baseline of 1961 to 1990 but that there had been a marked increase in variability. Also of interest is whether rainfall patterns have changed throughout the year, from month to month and between the seasons which is the subject of this post.

In order to provide some context, June 2012 was the wettest recorded June in 54 years with 130mm of rainfall which is almost double(196%) the average rainfall for the month and July is the fourth wettest with 75% more than average. Apart from this year, the five wettest Junes were followed by an average or below average July and likewise the five wettest Julies were preceded with a dry or average June. Data for August 2012 has yet to be published.

Over the fifty three complete years of data examined, there are wide variations in rainfall for each month as demonstrated by the monthly mean, maximum and minimum values plotted below. In some months the minimum values are almost zero while the maximum values may be almost three times the minimum.

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