The fuss about extreme rainfall last year tripped me into looking for myself. This led to an innovative analysis of Met Office areal time series for precipitation. There was little interest shown but also little criticism. I’m bringing up Windows 8.1 64 here, same hardware, testing various codebases.
As a wonder-if… the Met Office publish areal series for air temperature, Tmean, Tmax and Tmin. Daft idea, pull one file and eyeball, looks the same data format as rainfall. Do the lazy thing, copy code to a new directory, few trivial edits and hit go. It works. The results look sane.
Tmean for East Scotland, one of 68 plots. The four PDF, Tmean, Tmax, Tmin and Precipitation are linked later. Zoom to any scale works on what are postscript vector data, details can be seen.
A take-home from seeing the results is the episodic nature of weather. Mostly it is bouncing around as weather does but also there are sustained periods with less noise and perhaps floods or droughts, warm or chilly. The temperature data says we have recently had cool and then warm episode. Where this is notable it seems to last for around a year, as-if anything is a definite rule.
Another feature I’ve noticed is how an overall average tends to misleading for the UK because there are climatic regional effects, what applies to the south and east does not apply to the north-western Atlantic coast. and so on.
The drought of 1976 was regional, temperatures do not show the same effect, nor is this obvious if the whole UK is considered.
Southern England Tmax does show some effect without a clear sustained high bias. If it is dry it will tend to heat up quicker.
We see the same thing on a grander scale, this winter for example has been cold for the US north east but spring arrived very early for the US north west. Similarly Southern and South-Eastern Europe has been getting deluged in snow, state of emergency declared in parts of Bulgaria whereas southern England has had a fairly mild almost snow free winter. Much the same seems to apply more globally, as though there are paired regions.
This is characteristic of flicker noise, 1/f, chaotic.
[UPDATE] Doug Proctor asked in comments if sunshine data is available, yes but from 1929
Please read this section before looking at any of the plots because I mean innovative, you have to get your head around the meaning, not immediately obvious.
What is done
Areal data is computed by the Met Office from point station data to try and give a regional time series. All the usual caveats about stations changing apply.
The published time series Jan 1910 to Feb 2015 has the annual cycle removed by harmonic analysis, the result is then bent by a mathematical function to best fit Normal data, all done by computer code which optimises adjustment parameters for best fit (all my own code). Plots are then done.
The ranking tables give a clue on why getting your head around this is not so trivial
Tmean North & NE England, 2006 was hotter than 1938 but ranks lower because March (1938) is a colder time of year than July (2006), ie. the bias from annual cyclic variation has been removed. The statistical adjustment has no effect on ranking.
The statistical adjustment is attempting to equalise the significance of hot and cold to the same whereas in reality the data is asymmetric. This is of limited utility since in effect outliers, or extremes are part of weather. This goes off into special analysis most often done in hydrology to do with predicting civil engineering requirements, how large a flood drain is needed, how large a dam and so on.
This uses a hyperbolic function. See near end of May 2014 article here, and a region map if you need it. Code is unaltered apart from text and range of annual cycle.
As usual if you want data then ask, say what you need.
Post by Tim