On 29/10/2015 11:25, Eskimo Will wrote:


Hi Len, interesting stuff, but I have some questions about the graphs?

1. How consistent was the raingauge site over the years.

My experience of looking at Dartmoor gauges has revealed that just a
small change in location (even a few hundred metres) can make a
statistically sig. difference to rainfall. Cowsic is a case in question,
due to changes in aspect from one side of a valley to another.

2. In the 19th Century rainguage height was not consistent, in fact a
lot of gauges were elevated. Scientifically this was proven to produce
lower rainfalls than rainguages on the ground due to turbulence effects.

In my Dartmoor study I have been very careful to only use data where the
raingauge location has been consistent over the decades and where the
height of the gauge above ground has been consistent. I think that is
important.

3. Have you done a statistical Student's T test to measure significance
of the changes, I suspect that they are very sig (esp. winter). but with
the provisos of my points one and two above.

Jim, you need to look at your local area rainfall over the decades too,
if you can of course?

Will


Will. I've not been able to find anything from before 2000 anywhere.
Seems all the local weather stations in the county suddenly woke up
then, and records are pretty comprehensive after that date. All I can
say is that we never had any weather here in Northamptonshire before 2000!!!

jim

On 30/10/2015 09:17, Eskimo Will wrote:


Hi Len, again!

Having just read Jim's excellent response and queries in this thread,
I'm getting interested now in my own hypothesis which I'd dearly like to
test. If I gave you a list of "orographic enhancement days" (moist
SW'ly winds), would you be able to extract the Plymouth rainfall (and
wind) data for me? If we do this well it could end up as a super paper?
What do you think? Could be a lot of work for me initially though to
find the days, but that's science - hard work.

Will


Will. As I've stated elsewhere, I can't find anything before 2000, but
since then, Pitsford have kept very comprehensive records which are all
downloadable. This may or may not interest you, but they have a record
of wind, various temperatures and rainfall at 15 minute intervals from
2001 onwards. It can be found at
http://www.northantsweather.org.uk/archive/aws/ . They are .zip files
for each year, base format .csv which open in MS Excel by default. "15
minute wind records" caught my eye bearing in mind how part of this
conversation is unfolding. Being slap bang in the middle of the country,
they could be fairly indicative of the rest of the country.
(Home page at http://www.northantsweather.org.uk).

Pitsford's AWS is situated on the roof of the Pitsford Hall Grammar
School, about 5 miles north of Northampton. Ground level at the site is
about 400ft asl.

They have a page marked up "A review of 2011 and 2012 in the context of
a changing climate". It includes the following paragraph:
"However, there is every indication that not only is the timing of
rainfall changing, but also the nature of rainfall itself. When it does
rain, it is tending to rain harder and for longer. Again, this may be
the result of an increase in number of depression ‘trains’ tracking
across the UK – a product of the static position of the jet stream, but
it may also be the result of more energy in the atmosphere which points
to global warming as an ultimate cause. In Northampton, an analysis of
temperature data in 2010, suggests the county has seen an overall
increase in average temperatures of 0.1C since 1931. "

"Tending to rain harder" accounts for the severe drop in ground water
levels over the last few years, since most of that will result in
surface water run off.

Just found out Pitsford didn't start operating until 1998. That doesn't
excuse the county's other stations for not posting older records.

jim

Today, a slightly damper Northampton!

On Thursday, 29 October 2015 08:35:51 UTC, wrote:
"jbm" wrote in message ...
I am absolutely and thoroughly stuck on something the local council has
asked me to look into.

Over the last seven years, the rainfall in this area has been well below
normal for 5 of them. Currently, we are over 300mm short of what we would
normally have expected in that time. Doesn't sound a lot, but it
represents 6 months of normal rainfall.

In 2011 we had just under 400mm, 60% of normal, and the following year,
despite numerous thunderstorms, deluges and flood alerts along the River
Nene, several springs in the area dried up, and have not flowed since.
Result = steams with no water in them, local lakes well below level, with
any pollution entering them not being diluted sufficiently not to cause
problems. One lake lost all its waterfowl in July due to contamination
from fuel oil from a local industrial estate. What I have found is enough
evidence to prove that the ground water levels are severely depleted, with
the water table at least 300mm below what it was 5 years ago.

So I would appreciate it if some of you knowledgeable meteorologists out
there would care to hazard a guess at the following. Having experienced so
many dry years recently, what are the chances of getting some
exceptionally wet ones, with steady and moderate rain to start
replenishing the ground water, without the majority of it disappearing
straight into the rivers as surface run-off? What we need is a lot of
water, and I mean a lot, getting down to that water table as quickly as
possible. Any ideas anyone? We have to make a decision shortly as to what
to do with the lakes - leave them as they are, dredge out all the ****e
and see what happens, or fill them in and be done with it. And a
reasonably intelligent prediction on future rainfall might help in that
decision.

jim

a very dry and rainless Northampton

Hi Jim, I'm soon to give a public lecture on Dartmoor weather. As part of
that I have been looking into climate change on Dartmoor. At Princetown in
the 20th Century annual rainfall significantly (as revealed by an objective
T test) decreased. In the 21st Century, evidence from Haytor would suggect
that that drying trend has slowed but not reversed. My take on this is that
our climate is slowly getting drier in terms of annual rainfall. Basically I
think you're ****ed!

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Talking about liquid collection vessels

"think you're ****ed!"


Potty Mouth

On Friday, October 30, 2015 at 12:56:51 AM UTC, jbm wrote:
Right, I'll try to pass comment on all the relevant answers in one go.

Thank you all for your input. The best answer seems to be from Will:
"Basically I think you're ****ed!". Which corresponds very closely to my
assessment!!!

I too (like Alastair) am a retired engineer of the civil and
construction kind. I was asked to look into this because I am one of the
few (if any) people in Northampton who has first hand knowledge of the
local lakes, having been briefed very fully on their design and
construction back in the 1970's. A lot of the work I have done on this
concerns the geology and science behind ground water (N_Cook note - I
have subsidiary qualifications in Geology and Soil Mechanics), though in
a broad sense, not taking into account exact local conditions. While I
was preparing my report for the council, I received a report from an
adjacent local council on the flood assessment of a large housing
development about to take place alongside the stream that feeds the
lakes. I haven't been able to go through it in depth yet, but it appears
to contain a lot of information along the lines I was pursuing. There
are no figures available for the River Nene, which flows through the
county, but at Wansford near Peterborough its level is as low as it has
ever been. Flow rates earlier this year for the River Great Ouse in
Cambridgeshire were about 30% of what would be expected at that time of
year.

One thing I did learn was that the rainfall pattern throughout the year
was not what I expected. The summer months, Jul-Aug-Sep, are on average
about 10-15mm wetter than the rest of the year. Also those 3 months have
the least rain days, which means because of the heavier rate of rainfall
less water manages to get down to the ground water because of its
intensity forcing more in the way of surface run-off.

What I have noticed over the last few years is the numbers of times I
hear reports of torrential downpours to the west of here, whilst we get
next to no or no rain at all. Same applies to the east of us, but not so
noticeable. So it would appear that here in the East Midlands, and
especially in Northamptonshire, all the rain is falling elsewhere before
it gets to us. Never used to be like that - we always got more than our
fair share, not not so these days. Any ideas why that may be so?
Interesting, and somewhat puzzling, that Will is experiencing less rain
up in the hills, whilst Graham reports a slight increase down at the
seaside! Thought that would have been the other way round.

Thanks for those graphs, Len. Although you are a couple of hundred miles
away, they reflect very accurately what we had here in 2011, a very dry
year (60%), and 2012, a very wet year (130%). Unfortunately, most of
that 2012 total fell during thunderstorms, and I reckon sweet sod all
got down to the ground water. Probably more got down there in 2011. As
to water usage, the main reservoir in the area, Pitford, is in the next
catchment area to the west, though it relies on water extraction from
the River Nene to keep it going. Grafton Water is too far away to worry
us. Sywell Reservoir, within our catchment area, was decommissioned some
years ago, so no longer enters the equation. It is now used for purely
recreational purposes (fishing).

So far I have been unable to find any rainfall records for this area
from before 2000. What I have got, however, is a full record of monthly
rainfall since Jan 2006. Since then, by my reckoning, we are about 260mm
= 4% short of what we should have had. Bernard in Wokingham, about 50
miles south of here, has had 20% more. Which sort of emphasises my
belief that something is stopping the rain getting here.

And finally, in answer to Alastair's "So what ever you decide will be
wrong!", no I won't, because after receiving an email earlier this
evening I won't be making any decision in the foreseeable future. I am
stepping back from this for a while. One of our local councillors, much
against the wishes of me and someone I am working with on this, is going
to raise the matter at a full council meeting shortly, and from what we
understand he is going to push for the first lake to be dredged out to
remove the residual pollution and build up of silt. What he doesn't
realise yet (because he has already been cut out of the loop by
everybody concerned over his behaviour on a related matter - his only
interest is in scoring political points over the other parties) it that
silt is the result of a bank collapse alongside some houses, and if it
is allowed to continue or accelerate, those houses will be at risk of
falling down. Our other councillor has been made fully aware of the
situation, as have the Chief Executive and Assets manager of the
council. 2nd councillor has been instructed to shoot first councillor
down by revealing these findings at the meeting and telling him to make
sure of his facts before shouting his mouth off. I wish I could be there
to see and hear it all! I hadn't wanted this to get political, but it is
now out of my hands, for the time being at least.

Well, the general consensus of opinion seems to be no one here has any
bloody idea if we are going to get any rain. Fair enough I accept that,
and is basically what I expected. Will's "Basically I think you're
****ed!" sums it up perfectly.

jim

Northampton-under-Desert

Jim,

I have just come across this paper which you might find interesting:
https://www.researchgate.net/publica...gdom#full-text

Cheers, Alastair.

On 02/11/2015 09:40, Alastair wrote:


Jim,

I have just come across this paper which you might find interesting:
https://www.researchgate.net/publica...gdom#full-text

Cheers, Alastair.



Thanks for that Alastair. Looks interesting, more so because we were
slap bang in the middle of the drought order issued in June 2011.

Anyone else still reading this, since my last post I have managed to
find the complete historical rain data (monthly rain totals) from 1880
to 1997 for the county. I already have a similar set for 2006-2015. If I
scratch my way through the Pitsford site I should be able to fill in the
gap, though they do have a tendency to put similar sets of data for
different years in different sections. That's school kids for you!

jim, Northampton