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View Poll Results: Witch
London 51 61.45%
Helsinki 32 38.55%
Voters: 83. You may not vote on this poll

 
 
Old 09-18-2013, 11:01 PM
 
Location: Mid Atlantic USA
12,097 posts, read 9,630,326 times
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Quote:
Originally Posted by B87 View Post
Those sunshine figures are from Southsea.

Why does everywhere else in Europe show an increase in sunshine, when switching from CS to electronic? Paris and Berlin now have about 100-200 hours more than London, when they used to have the same or less. Warsaw used to record less sun than London but now records crazy numbers.

That is the closest station to Portsmouth and the one that gives you actual sunshine hours data for Portsmouth. The location is 7 miles from Portsmouth.

As far as the CS vs Auto in the UK, take it up with your Met Office. The article is right there for you to read. You have lots of days with passing clouds apparently and it inflates the sun hours using CS.

You have been on here telling us that they are adjusting the numbers down to CS but never gave any proof. That document shows they are actually doing the opposite. The sun hours using Auto are actually lower for London and elsewhere using the 120W standard. That is right in the article clearly spelled out. Why did you tell us they were adjusting the numbers down? Was there some article you can link to that explained that?
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Old 09-19-2013, 01:35 AM
B87
 
Location: Norwich, UK
10,824 posts, read 6,928,098 times
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Quote:
Originally Posted by tom77falcons View Post

You have been on here telling us that they are adjusting the numbers down to CS but never gave any proof. That document shows they are actually doing the opposite. The sun hours using Auto are actually lower for London and elsewhere using the 120W standard. That is right in the article clearly spelled out. Why did you tell us they were adjusting the numbers down? Was there some article you can link to that explained that?
Every other country that has switched from CS to auto has seen an increase in sunshine hours, so I assumed that they would adjust them down for the UK as well (also that article I posted previously shows the difference between a CS-calibrated recorder, and one that just measures 100W/m2, which is ridiculously overinflated). It doesn't make any sense for everywhere else to record higher hours of sun with auto, but the UK somehow has lower readings (eg Paris, which went from 1630 hours to 1740, Berlin went from 1625 to about 1800, and Warsaw from 1570 to 2200). London has remained unchanged. In reality, London is as sunny as Paris and Berlin, and sunnier than Warsaw.

The Kew CS sensor has an average burn threshold of 0.2cal/min/cm2 or 139.5W/m2, CS recorders in general can have a burn threshold between 105-270W/m2. It makes no sense that an instrument would record more sunshine with a stricter threshold (139W/m2), than the WMO standard (120W/m2).

Regarding the Southsea station, I believe FlamingGalah knows more about that. I think it requires access to the Met database (not every Met Office station has data available on their website, eg St James's Park).

Last edited by B87; 09-19-2013 at 02:05 AM..
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Old 09-19-2013, 07:08 AM
 
21,952 posts, read 11,610,925 times
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Quote:
Originally Posted by B87 View Post
You also have Chicago which used to use a sunshine recorder that has a burn threshold of 260W/m2, and averaged 2600 hours of sun.

Yes, it produces a similar sunshine figure for Chicago as the Foster which records at 87watts... You can't really compare these instruments because they all operate differently. Marvin does have a high burn threshold, and also a lower sensitivity but it records both direct and direct irradiation. The Foster starts recorder at a low threshold but is highly accurate, while the CS is subject to errors.



Quote:
RWood said he thought Chicago barely had 2100 hours when he spent a year there.
I've lived here all my life, and I couldn't tell you how many hours of sun we get on a yearly basis, only if it was sunnier or cloudier than the year before. For example 2013 is cloudier then 2012. Or 2009 was very cloudy.


I would imagine that if a there was a CS recorder here it would record around 2300 hours slashing about 300 hours.






Quote:
Originally Posted by B87 View Post
Every other country that has switched from CS to auto has seen an increase in sunshine hours, so I assumed that they would adjust them down for the UK as well (also that article I posted previously shows the difference between a CS-calibrated recorder, and one that just measures 100W/m2, which is ridiculously overinflated). It doesn't make any sense for everywhere else to record higher hours of sun with auto, but the UK somehow has lower readings (eg Paris, which went from 1630 hours to 1740, Berlin went from 1625 to about 1800, and Warsaw from 1570 to 2200). London has remained unchanged. In reality, London is as sunny as Paris and Berlin, and sunnier than Warsaw.
So the increase after the switch from the CS recorder to the automated sensors was +10% Berlin and 4% in Paris but Warsaw increased by nearly 30%?? Why such a big discrepancy?


I realized something.... When I had a correspondence with one of our local met offices about sunshine, they had sated that the difference between the Foster and the WMO standard is usually only a few minutes a day to up to an hour in "extreme cases". That was a comparison with the Kipp and Zonen which is the WMO standard and NOT a comparison between the Foster and the CS. This leads me to make the assumption that if we theoretically knock of about 300 hour from Chicago's annual sunshine to go down to CS levels, then we would be raising them again by 100-200 hours (which is the increase that Berlin and Paris saw) if we use the Kipp and Zonen device. So about 2400-2500 hours





Quote:
The information comes from an instrument called a sunshine recorder. It consists of two photoelectric cells, one exposed to the direct rays of the sun and another shielded from direct rays but otherwise exposed to diffuse skylight. When sun shines on the exposed cell, an electric signal is generated--a signal that is not balanced by the shaded cell. This electrical imbalance trips a relay and activates a recorder that tallies the minutes of sunshine.

A new instrument being used today (and recommended by the World Meteorological Organization) is made by Kipp and Zonen Leaders in Radiation Equipment. It consists of three sensors--one that detects all direct and diffuse sunlight, and two others that look only at portions of the sky. Sunshine times are determined by differential measurements between the three sensors. Sunshine data from both systems are being collected by Midway Airport weather observer Frank Wachowski, and the results are being compared.
Dear Tom, You often make mention of the amount of... - Chicago Tribune
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Old 09-19-2013, 07:35 AM
 
Location: St Paul's Bay, Malta
11,482 posts, read 5,924,293 times
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Quote:
Originally Posted by tom77falcons View Post
I'd like to know where those sun hours for Portsmouth came from anyway, cause the Met Office site lists 1792 hours (Thorney Island) not the 1919 from Wiki.
The Wiki data claims "Regional Mapped Climate Averages". It's a map that lists 1750 to 1900 for the sunniest parts. It doesn't even list 1919 hours. Thorney Island shows the exact same color as Portsmouth, yet the actual sunshine data there is 1792 hours.
The figures for Southsea come from the now closed Met Office weather station which was situated right on the seafront. The data from that (& many other weather stations) is not made publically available. I have (had) access to the Met Office database for some research I was doing some time ago. A friend of mine at the University of Portsmouth (which used to be responsible for taking the daily readings from the weather station) still has access to the original log books, copies of which are kept at the University & he did the weather box on Wikipedia using the original readings (much easier than trying to use the Met Office database, which lists everything by date, not station!)...

Those regional maps on the Met Office site are for the period 1971-2000 & also in many cases are estimates, using grided data sets based on the nearest weather station, so anything that is the darkest orange has between 1750 & 1900 hrs of sunshine... Shanklin on the Isle of Wight & Bognor Regis are also the exact same colour, yet the sunshine figures for there are also both over 1900 hrs...

Quote:
Originally Posted by tom77falcons View Post
That is the closest station to Portsmouth and the one that gives you actual sunshine hours data for Portsmouth. The location is 7 miles from Portsmouth.
Thorney Island may only be 7 miles as the crow flies from Portsmouth, but it may as well be 70 miles away! It is further north than Portsea Island (Portsmouth) & in the summer especially it is really only the very southern coastal strips that see much more sunshine, as shower clouds form just inland & are pushed inland by our prevaling SW'ly winds. My Mum also lives a few miles north of Portsmouth & she will often complain of cloud or showers during the summer when it has been sunny here all day. Thorney Island also is much colder than Portsmouth during the winter as it is largely rural... So to compare Portsmouth to Thorney island is a bit like comparing apples to oranges
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Old 09-19-2013, 07:45 AM
 
Location: Finland
24,268 posts, read 17,563,761 times
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Paris Montsouris averages 1662 hours of sun annually. Places like Le Havre averages less sun than Portsmouth, despite using a smaller treshold.

Brussels, meteorogically just a stone throw away from London averages 1546 hours. How on earth could London have 500 hours more if using a different treshold?

And if you use some other methology than rest of the world, suck it up. It's up to you to alter your criteria.
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Old 09-19-2013, 07:51 AM
B87
 
Location: Norwich, UK
10,824 posts, read 6,928,098 times
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Weren't those Paris and Brussels averages recorded with CS though? Someone on another forum posted data showing that the past few years Paris and Brussels have both been averaging around 1800-2000 hours, using the 120W/m2 standard.
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Old 09-19-2013, 08:00 AM
 
Location: Finland
24,268 posts, read 17,563,761 times
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Quote:
Originally Posted by B87 View Post
Weren't those Paris and Brussels averages recorded with CS though? Someone on another forum posted data showing that the past few years Paris and Brussels have both been averaging around 1800-2000 hours, using the 120W/m2 standard.
Well, maybe Finland did as well? Maybe we average 2500 hours with the 120W/m2 standard. Who knows.

BTW, looks that London's irradiance in July is less than Helsinki's in May by MJ/m2.


Is the 109-110 days with over 1mm precipitation correct for London?

Helsinki's figures are 115 (Airport) and 111 (Kaisaniemi).
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Old 09-19-2013, 08:19 AM
 
Location: Mid Atlantic USA
12,097 posts, read 9,630,326 times
Reputation: 5275
Quote:
Originally Posted by B87 View Post
Every other country that has switched from CS to auto has seen an increase in sunshine hours, so I assumed that they would adjust them down for the UK as well (also that article I posted previously shows the difference between a CS-calibrated recorder, and one that just measures 100W/m2, which is ridiculously overinflated). It doesn't make any sense for everywhere else to record higher hours of sun with auto, but the UK somehow has lower readings (eg Paris, which went from 1630 hours to 1740, Berlin went from 1625 to about 1800, and Warsaw from 1570 to 2200). London has remained unchanged. In reality, London is as sunny as Paris and Berlin, and sunnier than Warsaw.

The Kew CS sensor has an average burn threshold of 0.2cal/min/cm2 or 139.5W/m2, CS recorders in general can have a burn threshold between 105-270W/m2. It makes no sense that an instrument would record more sunshine with a stricter threshold (139W/m2), than the WMO standard (120W/m2).

Regarding the Southsea station, I believe FlamingGalah knows more about that. I think it requires access to the Met database (not every Met Office station has data available on their website, eg St James's Park).

Did you read the article by the PhD's? Send them an email and ask your questions. Until I hear otherwise, I will assume that the sun hours for London and elsewhere in the UK is not going to go up in any dramatic way using Auto. The article clearly spells out the diff is because of solar elevation and passing clouds which extend the burn time on the card, while Auto doesn't have that issue. It is worse in summer than winter. On fully sunny days and overcast days no problems. It is days with sun and clouds that they have the big discrepancies. There was another article they referenced on the Met website which supposedly refined it even further. I can't find that article. If you found that article maybe it would show some updated correction numbers. Who knows, maybe they have changed to adjust the Auto numbers down to CS in some locations. But that article I posted didn't mention anything about some areas being different than others.
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Old 09-19-2013, 08:23 AM
B87
 
Location: Norwich, UK
10,824 posts, read 6,928,098 times
Reputation: 2514
Quote:
Originally Posted by Ariete View Post
Well, maybe Finland did as well? Maybe we average 2500 hours with the 120W/m2 standard. Who knows.

BTW, looks that London's irradiance in July is less than Helsinki's in May by MJ/m2.


Is the 109-110 days with over 1mm precipitation correct for London?

Helsinki's figures are 115 (Airport) and 111 (Kaisaniemi).

The south coast has higher irrandiance than Helsinki in summer, despite having fewer sun hours.

Yes, those figures are correct. Heathrow and Greenwich both have 109 days. Heathrow has 145 days where a trace is recorded.
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Old 09-19-2013, 08:26 AM
 
Location: Mid Atlantic USA
12,097 posts, read 9,630,326 times
Reputation: 5275
Quote:
Originally Posted by flamingGalah! View Post
The figures for Southsea come from the now closed Met Office weather station which was situated right on the seafront. The data from that (& many other weather stations) is not made publically available. I have (had) access to the Met Office database for some research I was doing some time ago. A friend of mine at the University of Portsmouth (which used to be responsible for taking the daily readings from the weather station) still has access to the original log books, copies of which are kept at the University & he did the weather box on Wikipedia using the original readings (much easier than trying to use the Met Office database, which lists everything by date, not station!)...

Those regional maps on the Met Office site are for the period 1971-2000 & also in many cases are estimates, using grided data sets based on the nearest weather station, so anything that is the darkest orange has between 1750 & 1900 hrs of sunshine... Shanklin on the Isle of Wight & Bognor Regis are also the exact same colour, yet the sunshine figures for there are also both over 1900 hrs...



Thorney Island may only be 7 miles as the crow flies from Portsmouth, but it may as well be 70 miles away! It is further north than Portsea Island (Portsmouth) & in the summer especially it is really only the very southern coastal strips that see much more sunshine, as shower clouds form just inland & are pushed inland by our prevaling SW'ly winds. My Mum also lives a few miles north of Portsmouth & she will often complain of cloud or showers during the summer when it has been sunny here all day. Thorney Island also is much colder than Portsmouth during the winter as it is largely rural... So to compare Portsmouth to Thorney island is a bit like comparing apples to oranges
So 7 miles away and the sun hours increase by over 120 hours. How come everyone was saying that the difference between Detroit and Windsor couldn't be correct, yet the two airports are much further than 7 miles. Portmsouth must be some little isolated island of sunshine then compared to places surrounding it.
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