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Increasing annual rainfall

Posted: Sat Jan 09, 2016 10:04 am
by Len Wood
The annual rainfall for 2015 in Wembury was 1071.1 mm, which was very close (102%) to the 2001-2015 average.

However the graph for 2001-2015 shows an increasing trend.

The standard deviation is +/- 156 mm which gives a measure of expected variability about the average.
The magnitude of the trend with a linear fit is 233 mm.
This is greater than the standard deviation and therefore can be considered significant.
Annual rain.jpg
Annual rain.jpg (77.49 KiB) Viewed 7347 times

Re: Increasing annual rainfall

Posted: Sat Jan 09, 2016 8:14 pm
by Graham Easterling
In Penzance, mean rainfall:-
1961-1990 1140.0mm
1971-2000 1189.3mm
1981-2010 1219.6mm
2010-2015 1245.1mm

So there seems to have been an gradual upward trend for the last 50 years!

I also noticed your post on USW about lack of warming in reccent years. In Penzance, whilst the temperature has been flat for the last 10 years, there was a distinct upward trend for a good time up until then.

Mean Annual Temperature
1961-1990 11.1C
1981-2010 11.6C

Re: Increasing annual rainfall

Posted: Sat Jan 09, 2016 9:14 pm
by Martin Rowley
Graham Easterling wrote:In Penzance, mean rainfall:-
1961-1990 1140.0mm
1971-2000 1189.3mm
1981-2010 1219.6mm
2010-2015 1245.1mm

So there seems to have been an gradual upward trend for the last 50 years!
... Using Hurn data (ex. MetO web site) for the periods Graham quotes above:

1961-1990 790.1 mm
1971-2000 812.4 mm
1981-2010 835.2 mm
2010-2015 917.5 mm [ 6 years - skewed strongly by the two wet years 2012 & 2014]

Martin.

Re: Increasing annual rainfall

Posted: Sun Jan 10, 2016 2:45 pm
by John Wilson
A graph of my annual rainfall from 1994 (when readings began) is very similar to that of Len's. So definitely a gradual but significant increase over a fairly short time (20+ years). Does this hold for the whole of the UK? Have some areas experienced a greater increase than others? A small research project for COL members!
My December rainfall was 82.6mm; 141% of long term average.
Regards to all
John