"Ken Cook" wrote in message
...
On Thursday, 29 October 2015 08:35:51 UTC,
wrote:

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.
Will

Hi, Will,
Hmmm, how far north would you be tempted to travel to lecture? NE RMetSoc
renowned for looking after their speakers. We had Colin Clark up from
Bruton last month.
Here's hoping.


Hi Ken, happy to do my Dartmoor talk up north as I have grandchildren now in
Leeds and it would be a good excuse to pop in and see them? But would you
northern folk be interested in Dartmoor weather? I *could* slant it more
towards innovative use of AWS data.
Pop me an e-mail and we can discuss further. My fees are very reasonable :-)

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

"N_Cook" wrote in message
...
Another thing on the geology aspect. Research in neaghbouring areas to see
if springs have suddenly emerged or extra river flow as changes
underground can occur to divert groundwater

Yes we often neglect geology! Mainly, I think because we are meteorologists
:-)
Nature does not respect individual science disciplines!

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

On Thursday, 29 October 2015 11:35:09 UTC, wrote:
"Ken Cook" wrote in message


Hi Ken, happy to do my Dartmoor talk up north as I have grandchildren now in
Leeds and it would be a good excuse to pop in and see them? But would you
northern folk be interested in Dartmoor weather? I *could* slant it more
towards innovative use of AWS data.
Pop me an e-mail and we can discuss further. My fees are very reasonable :-)

Hi, Will
Thanks (:0)
I'll be in touch very soon.
Ken

The exposure of long term gauges is significant. Trees/bushes grow, houses get built et cetera, et cetera. I've seen two identical gauges, five metres apart, record differences of 5% due to differences in exposure. The condition and set up of the gauge is also important.

On Thursday, October 29, 2015 at 8:35:51 AM 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)
---------------------------------------------

For Penzance:-

Mean Annual Rainfall
1961-1990 1140mm (call this 100%)
1971-2000 1182mm 104%
1981-2019 1219mm 107%
2000-2014 1228mm 108%

So a consistent upward trend, albeit gentle.

Nothing like the decrease in number of gales, which has been quite dramatic over the last 20 years.

Graham
Penzance

On Thursday, October 29, 2015 at 2:08:50 AM UTC, jbm wrote:
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.

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,

I am not a professional meteorologist, but I have been studying climate change since I retired from engineering about 20 years ago.

As an ex-engineer I would say Sod's Law rules, it is a corollary of the Second Law of Thermodynamics. So what ever you decide will be wrong! For instance when there was a long drought in South East Australia, they built a large desalination plant. As soon as it was built the rain returned. Here in the UK, we had a drought and the minister in charge brought in water rationing. That was followed by the wettest summer ever. So my advice is take preventative measures and with a bit of luck they will not be needed. (If you don't take them they will :-)

As I keep saying, both weather and climate are chaotic. So past performance is not a guide to future behaviour, nor can you rely on the fallacious Law of Averages to buck a trend.

The government produced a book about 20 years ago where they forecast how climate change would affect the UK. The conclusion was that the north would get wetter and the south drier. I can't find my copy of that book but if the dividing line moves south then you could become wetter or vice versa.

HTH,

Cheers, Alastair.

On Thursday, 29 October 2015 11:25:16 UTC, wrote:
"Len Wood"



Hi Jim,
If you look at the record of annual rainfall for Plymouth 1874 to 2014 you
see how variable it is with no longterm trend, but clearly trends on the
decadal timescale.

You can see an increasing trend after the drought of the mid seventies,
and then a decrease and now slight increase again.

I have also put in dropbox the link to the graph of summer and winter
rainfall.
There is a significant increasing trend in winter rainfall and a less
convincing decrease in summer rain. Hence no trend in annual rainfall over
the longterm.

https://www.dropbox.com/s/u0s7p9kroj...02014.jpg?dl=0

https://www.dropbox.com/s/9lfjie7ko4...0rain.jpg?dl=0

If I was you Jim I would hold fire, but if the water usage has gone up in
recent years and/or the surface morphology has changed then you are stuck.



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

You are of course right Will to question the homogeneity of the record.
1874 to 1979 is for Plymouth Hoe Observatory. 36 m asl
1980 to 2014 is for Plymouth Mount Batten. 45 m asl
Mount Batten is about 1.8 km to SE of the Hoe site.

In 1991 I was asked by the Association of British Climatologists (now defunct) to give a talk at their meeting in Durham on the 'History of Observatories' about Plymouth Hoe Observatory.
I did a fair amount of research for this, from local libraries, but also a trip to the Met Archive in Bracknell.
There is an element of vagueness about the early record because there are never any photos of the site in early times, although the location as a name remains the same.

2)There was no elevated rain gauge at the Hoe as far as I know.

The dear old Met Office provide the record from 1874 and label it Plymouth Mount Batten! Mount Batten opened in 1921 when measurements began. The Met enclosure move up the Mount Batten peninsula in 1940 during WW2.

A comparison of measurements on the Hoe and at Mount Batten shows there is not a big difference.

https://www.dropbox.com/s/z52svn3b63...red.j pg?dl=0

https://www.dropbox.com/s/2xovemf7r8...tions.doc?dl=0

Will, have you seen my 2004 paper in Weather on Regional trends?

https://www.dropbox.com/s/lx3lrc47c0...0NAOI.pdf?dl=0

I have quite a bit of info on the Plymouth record if you want it.

3)And finally, yes, the increasing trend in winter rainfall is statistically significant.

Len
Wembury, SW Devon

------------------------------------------------------------------------------

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

"Len Wood" wrote in message
...
On Thursday, 29 October 2015 11:25:16 UTC, wrote:
"Len Wood"



Hi Jim,
If you look at the record of annual rainfall for Plymouth 1874 to 2014
you
see how variable it is with no longterm trend, but clearly trends on
the
decadal timescale.

You can see an increasing trend after the drought of the mid seventies,
and then a decrease and now slight increase again.

I have also put in dropbox the link to the graph of summer and winter
rainfall.
There is a significant increasing trend in winter rainfall and a less
convincing decrease in summer rain. Hence no trend in annual rainfall
over
the longterm.

https://www.dropbox.com/s/u0s7p9kroj...02014.jpg?dl=0

https://www.dropbox.com/s/9lfjie7ko4...0rain.jpg?dl=0

If I was you Jim I would hold fire, but if the water usage has gone up
in
recent years and/or the surface morphology has changed then you are
stuck.



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?


You are of course right Will to question the homogeneity of the record.
1874 to 1979 is for Plymouth Hoe Observatory. 36 m asl
1980 to 2014 is for Plymouth Mount Batten. 45 m asl
Mount Batten is about 1.8 km to SE of the Hoe site.

In 1991 I was asked by the Association of British Climatologists (now
defunct) to give a talk at their meeting in Durham on the 'History of
Observatories' about Plymouth Hoe Observatory.
I did a fair amount of research for this, from local libraries, but also a
trip to the Met Archive in Bracknell.
There is an element of vagueness about the early record because there are
never any photos of the site in early times, although the location as a
name remains the same.

2)There was no elevated rain gauge at the Hoe as far as I know.

The dear old Met Office provide the record from 1874 and label it Plymouth
Mount Batten! Mount Batten opened in 1921 when measurements began. The Met
enclosure move up the Mount Batten peninsula in 1940 during WW2.

A comparison of measurements on the Hoe and at Mount Batten shows there is
not a big difference.

https://www.dropbox.com/s/z52svn3b63...red.j pg?dl=0

https://www.dropbox.com/s/2xovemf7r8...tions.doc?dl=0

Will, have you seen my 2004 paper in Weather on Regional trends?

https://www.dropbox.com/s/lx3lrc47c0...0NAOI.pdf?dl=0

I have quite a bit of info on the Plymouth record if you want it.

3)And finally, yes, the increasing trend in winter rainfall is
statistically significant.

Len
Wembury, SW Devon

------------------------------------------------------------------------------

Hi Len, no I haven't seen that paper. Unfortunately I cannot seem to
download from dropbox as it is asking for my account and I don't use
dropbox. Could you e-mail it to me, it looks interesting? Thanks.

One thing about Dartmoor, Graham has pointed out that gale frequency has
dropped right off and it is possible that the decrease in wind speed has
decreased the orographic enhancement (which is where we get a lot of our
rain). So it is perfectly possible for rainfall to decrease or stay the same
on high ground and increase on the coast, especially in winter!
Have winds speeds decreased in Plymouth like Penzance?

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

"Eskimo Will" wrote in message
...

"Len Wood" wrote in message
...
On Thursday, 29 October 2015 11:25:16 UTC, wrote:
"Len Wood"



Hi Jim,
If you look at the record of annual rainfall for Plymouth 1874 to 2014
you
see how variable it is with no longterm trend, but clearly trends on
the
decadal timescale.

You can see an increasing trend after the drought of the mid
seventies,
and then a decrease and now slight increase again.

I have also put in dropbox the link to the graph of summer and winter
rainfall.
There is a significant increasing trend in winter rainfall and a less
convincing decrease in summer rain. Hence no trend in annual rainfall
over
the longterm.

https://www.dropbox.com/s/u0s7p9kroj...02014.jpg?dl=0

https://www.dropbox.com/s/9lfjie7ko4...0rain.jpg?dl=0

If I was you Jim I would hold fire, but if the water usage has gone up
in
recent years and/or the surface morphology has changed then you are
stuck.



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?


You are of course right Will to question the homogeneity of the record.
1874 to 1979 is for Plymouth Hoe Observatory. 36 m asl
1980 to 2014 is for Plymouth Mount Batten. 45 m asl
Mount Batten is about 1.8 km to SE of the Hoe site.

In 1991 I was asked by the Association of British Climatologists (now
defunct) to give a talk at their meeting in Durham on the 'History of
Observatories' about Plymouth Hoe Observatory.
I did a fair amount of research for this, from local libraries, but also
a trip to the Met Archive in Bracknell.
There is an element of vagueness about the early record because there are
never any photos of the site in early times, although the location as a
name remains the same.

2)There was no elevated rain gauge at the Hoe as far as I know.

The dear old Met Office provide the record from 1874 and label it
Plymouth Mount Batten! Mount Batten opened in 1921 when measurements
began. The Met enclosure move up the Mount Batten peninsula in 1940
during WW2.

A comparison of measurements on the Hoe and at Mount Batten shows there
is not a big difference.

https://www.dropbox.com/s/z52svn3b63...red.j pg?dl=0

https://www.dropbox.com/s/2xovemf7r8...tions.doc?dl=0

Will, have you seen my 2004 paper in Weather on Regional trends?

https://www.dropbox.com/s/lx3lrc47c0...0NAOI.pdf?dl=0

I have quite a bit of info on the Plymouth record if you want it.

3)And finally, yes, the increasing trend in winter rainfall is
statistically significant.

------------------------------------------------------------------------------

Hi Len, no I haven't seen that paper. Unfortunately I cannot seem to
download from dropbox as it is asking for my account and I don't use
dropbox. Could you e-mail it to me, it looks interesting? Thanks.

One thing about Dartmoor, Graham has pointed out that gale frequency has
dropped right off and it is possible that the decrease in wind speed has
decreased the orographic enhancement (which is where we get a lot of our
rain). So it is perfectly possible for rainfall to decrease or stay the
same on high ground and increase on the coast, especially in winter!
Have winds speeds decreased in Plymouth like Penzance?


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