Hexa Pascals

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David Frydman
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Hexa Pascals

Post by David Frydman »

I check the weather when I observe.

It is now 1018 Hexa Pascals.

What are these and what is wrong with millibars?

David
David Frydman
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Post by David Frydman »

Sounds like something you eat.
Fruit Pastilles or maybe a sauce condiment.

Regards, David
David Frydman
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Post by David Frydman »

O.K.
Although the voice message sounded very clear the meteorologist actually was using hectopascals.

1 hectopascal = 1 hPa = 100 pascals = 100 Pa = 1 millibar = 1 mbar.

Apparently the hectopascal is an old unit which few use.
If anything they use a kilopascal.
Why this young sounding meteorologist was using hectopascals I don't know.

Others just say QNH 1018 QFE 1014. The latter takes into account height above mean sea level.

Regards, David
LeoLion
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Post by LeoLion »

Hi David , Just to correct your comment re 'an old unit' this quoted from the NPL website ' (1) Following the 8th Congress of the World Meteorological Organization, from 1 January 1986 the term hectopascal (hPa) is preferred to the numerically identical millibar (mbar) for meteorological purposes. This choice was made, despite the fact that hecto (x 100) is not a preferred multiple in the SI system, to avoid having to change the numerical values on barometer scales.' The source for the quote is the NPL http://www.npl.co.uk/reference/faqs/pressure-units. It dates from 2010. Hope that URL works OK
I prefer oktas for cloud cover but have been taken to task as to why I did not use per cent cloud cover !
I had the joys of unit changes all through my laboratory life. Best wishes :)
David Frydman
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Post by David Frydman »

Thanks Leo the Lion,

It was the first time I heard it today, and I thought it strange to have obviously the same or similar units described differently.

It is like weights are listed in tons and tonnes. Slightly different.
And K is 1024 not 1000 but people refer to 1000 as K.

Most confusing.

We should have kept to £.s.d. farthings and bushels.

Smiley face does not seem to work on my computer.

Regards, David

I think the U.S. still measure pressure in inches and the Russians use metres for altitude.
Also the separation distance in height for modern aircraft is down to 250ft. in cases.
Cliff
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Post by Cliff »

Dear David and Leolion
Hopefully this is not another case of scientists baffling the general populace with science.
I was given a very nice electronic weather centre for my birthday this year. It provides outside temperature, wind speed and airpressure information information which appears on a small receiver conveniently placed in our living room. I have no intention of using the weather centre to produce serious scentific results just to be used for my own fun. The readout with regards air pressure is in "millibar" units.
Irrespective of "weather" the weather people use "millibars" or fruitpastils they only seem to provide forecasts up tp 5 days ahead.
Sorry you caught me in a bad mood.
Best wishes from Cliff
brian livesey
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Post by brian livesey »

Glad to see that you are back to your grumpy old self, Cliff. I have a DIY weather station: I glance at the sky, sniff the air and stick my finger up to the wind. It usually means there's rain on the way.
brian
Cliff
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Post by Cliff »

Dear Brian
Thanks for your comments !
I think I might be more grumpy than ever now but less confident in expressing my feelings.
My birthday weather station may be a bit over my requirements. It took me quite a few days to set it up. The "windometer" is only 2 metres above ground level which I suspect is much too low down to provide really good readings because of turbulence caused by nearby houses. (I noticed John Fletcher'ssimilar looking equipment displayed a recent Popular Astronomy seems to be maybe as much as 10 metres up).
at this stage I do not intend to keep detailed weather records but in viwe of my general interest in such things as climate matters and my declining interest\ability to observe the night sky, I thought the weather centre wouldhelp keep my "amateur" interest in popular science going. On top of which my wife is quite interested in the weather centre equipment as well.
Best wishes from Cliff
.
David Frydman
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Post by David Frydman »

It seems the hectopascals are here to stay.
Now a youngish sounding Welsh lady also gives the weather with these units.
It was not as clear as previously but obviously millibars are out and fruitpastils are the new flavour.

Regards, David
David Frydman
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Post by David Frydman »

This morning thick variable fog.
The Scottish gentleman just earlier first clearly said 1020 millibars.
Then a few minutes later 1020 hectopascals.

Sounded a bit like the Ectoplasma in the film Ghostbusters.
The fog probably looked a bit like the Ectoplasma I suppose.

Regards, David.
David Frydman
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Post by David Frydman »

Did they really have to change millibars to hectopascals when they are identical and when even the weather people are confused?

Soon there will be the New Euro, which will be worth 1000 devalued old Euros.
The old Euro would buy you one shirt button.
The New Euro will buy buy you 1000, sorry 500, sorry 300 shirt buttons as changeover day progresses.

At least there doesn't seem to be any devaluation of the hectopascals, at least not today.

Regards, David
Cliff
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Post by Cliff »

Dear David
Millibars and are identical -
Are they ??????
Or are they NOT ?????
As Hamlet might have said or not said.
I have to admit I was horified the other day to read somewhere that the temperature of something measured in degrees Celsius is a very similar number to its temperature measured in Centigrade.
I nearly dropped cork legged when I went on to read that the Celsius and Centigrade values would probably be somewhere within a single degree of each other.
Like a fool I had thought that degrees Celsius and degrees Centigrade are exactly the same number - NOT SO or so I think it is, or isn't.
Apparentltly degrees Centigrade and Celsius are very similar but not really quite the same number.
I think the reason is answered by the famous old Irish story.
"If I were you I wouldn't start from here !"
It seems Centigrade started here but Celsius started over ther,e where there isn't exactly the same place.
However. apparently, presumably to avoid confusion, school children are still taught that Centigrade and Celsius temperatures are exacly the same number even though they aren't.
Best of luck from Cliff
PS -Whose been trying to kid me into thinking science is difficult to understand.
David Frydman
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Post by David Frydman »

Dear Cliff,
If you click onto LeoLion's link to the NPL above they explain carefully that they are identical, but there is no standard pressure as it is quite impossible to measure all pressures at all points on the globe and all sea levels to come up with this.
As you say, Cliff, somewhere in the fine print there may a difference but they have I think made them equal.
The same as there used to be 31,556,926.08 seconds in a year but they rounded it off and periodically add leap seconds when necessary. Apparently long term the Britisk clock at NPL is twice as accurate as the French or other world clocks.

Pressure is interesting to me.
About 8 years ago Jessops were clearing 8x25 Minox binoculars at a third the new price. They were new and include a barometer/altimeter.
This is so accurate that it shows a different height at table level or shoulder. It reliably measures to two or three feet.
The problem is I can nowhere get an initial fix as millibars are given to unit values. It is about 28 feet to a millibar when you change pressure at about sea level.
So I need a source of millibars/hectopascals/fruitpastils/ectoplasm to 0.1 accuracy and better to calibrate the binocular altimeter/barometer.
The best I can do is to take QNH/QFE readings from two or three local stations when the pressure everywhere is nearly steady and get it down to about 0.3 millibars.
There is no real requirement for this. It is just fascinating that such accurate barometers are available to the general public and with a very good binocular at a very low price.
Horace Dall made a barometer more than fifty years ago that changed readings if you put a book under it.

Some things are remarkably cheap. The local charity shop were given many ex large chain bookstore £15 or more radio controlled clocks with big digits and a projection device for putting the time and pressures on the ceiling at night plus a night light.
Nobody wanted them at £5 or £4 new. I ended up buying perhaps ten for £20 They all work perfectly but nobody wanted them at any price. They have been given as gratefully received gifts.
The general public don't seem to appreciate how very accurate these instruments are.
The point is these clocks are accurate throughout the year to better than one second and give very accurate pressures.
If I see a meteor or other transient astronomical event I can look at the nearest radio controlled clock and get an accurate time.
The AA battery lasts about two years and these clocks have worked reliably for five or more years.

I have always been keen on measurement.

Regards, David
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Post by David Frydman »

Dear Cliff,
Interested in nautical miles as they are meant to be one minute of arc on the equator, which actually varies because the Earth is not a perfect sphere but also not perfect measurements.
I assumed a nautical mile is 6,080 feet, and that 33 nautical miles is 38 statute miles of 5,280feet.
These measurements are important for astronomy to fix our position on the Earth.
But it seems that a nautical mile is about 6,076.1 feet or exactly 1,852 metres. It seems the 6,080 feet is actually the Admiralty mile.
Apparently the foot was slightly different all over the world only being standardised in 1959 when 3 feet or a yard was made to be 0.9144 metres.
The Earth's circumference at the equator is 40,075 km, but the real result is given to about a millimetre and varies with the system chosen for the Earth's shape.
It is also about 24,901.5 miles.

Why is this important?
Well for astronomy but also for shipping and aircraft and spacecraft.

I suppose altitude for aircraft could switch to metric, but would probably result in air crashes for a while.
Instead of 1000ft and 250ft gaps it could be 400 metres and 100 metres I suppose.

There are still a lot of non metric units.
Despite large forests in Finland they still I think measure wood in inches, say 4x2 inches but lengths in metres.

So still a mixed up world.

The SI units should not really include hecto only kilo.
So hectopascal is also really a made up unit.

Even young pilots are now using hectopascals.

I don't like hectopascals for the following reasons.

a) It is a tongue twister. millibars is easier.
b) If they were going to change they should have used something simpler such as Simples.
The pressure is now 1018 simples.
c) I just don't like change but unfortunately there is one certainty. Things will change.

Regards, David
Cliff
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Post by Cliff »

Dear David
I too have some interest in things like types of measurements that you have been talking about.
Some of the things you mention were already known by me but a few I might not have known the details about.
I think I learned not to be to dogmatic about such things (even supposed accurate measurements) many years ago as a trainee engineer, when I realised measuring things accurately could be trickier than you (or perhaps rather I) might think.
I now find such things amusing, as from reading your posts, I suspect you do yourself. Whilst sometimes I find some related matters frustrating.
One of my many frustrations has been in connection with "sporting" matters.
The modern Olympic Marathon for example is nowadays decided to be 25 miles plus a few hundred yards. I understan 25 miles was to be the distance but the extra bit was added so that the race would end opposite the royal spctators box. Whilst from what I gather the original Ancient Greek legendary Marathon run (by a runner covered a distance of only about 24 miles and the chap who supposedly ran it might actually never have run it at all.
Up until a few years ago I believe there was no such thing as World Marathon Record because it was properly said no two marathon courses are alike.
But it seems pundits like TV presenters like to provide their viewers with the usual overkill of information associated with modern life.And so recently I think I hear the pundits talking about World Record Marathon runs more and more ?
Is it any wonder the world is going to pot ?
The World's population increases relentlessly and the powers that be treat the matter the same way as they treat bankers bonuses. Meanwhile scientists tinker with things that really matter changing millibars to fruitpastils - but perhaps that's being very unfair.
One thing I would mention though is related to something being discussed elsewhere on this forum - the speed\velocity of light.
Calling it speed or velocity doesn't matter much to me personally, and I haven't joined in the recent discussions. However, from what I gather the speed of light is approximately 300.000 kilometres a second in a vacuum, But I am just now reading "The Quantum Universe - everything that can happen will happen".
I haven't finished it yet but I think it will eventually get round to telling me that vacuums dont exist - well not in out Universe anyway !
Best wishes from Cliff
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