November 21, 2009
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The Barometer Dial
David_N
Posts: 7
 Joined: 2008-02-07

Hi Doug --

I live in Canada under the metric system. We are blessed with a highly sophisticated weather forcasting organization (Environment Canada) at www.theweathernetwork.com . When checking my local weather, barometric pressure is stated in kPa, is this the same as mb?

I inherited a borometer from my father who joined the Merchant Navy based in New Zealand in 1931. The dial calibrations are in inches of mercury ranging from 27"to 31.9". Is there a formula to convert inches of mercury to kPa? 

‹ Temperature shifts - how do they happen? Weather and Waves ›

Submitted by David_N on Tue, 03/04/2008 - 19:26.

TheWeatherMan
Posts: 23
 Joined: 2007-12-05

I have some good news and some bad news, David.  The good news is that it is very easy to convert pascals (or in your case kilopascals) into millibars.  The bad news is that the conversion from inches of mercury to millibars is down right ugly.

First...some background...the standard atmosphere is considered approximately 1.013 bars of pressure (1013 millibars)...or 29.53 inches of mercury. 

 

SO...the easy conversion.  1 hPa= 1 millibar.  A hectopascal (hPa) is 0.1 kilopascals (kPa).  So...1 kPa=10 millibars.  Phew...now let's keep going.

Since 1013 millibars (1.013 bars)=29.53 inches of mercury...to get the conversion to kilopascals...we must divide by 10.    You get 101.3 kPa=29.53 

The formula is the ugly part...to convert inches of mercury to millibars...

Inches of mercury X 33.76 = millibars

To really be precise...you need to factor in the temperature.  My advice is to google "inches of mercury conversion" to get all the types of pressure conversions in a table format.   

 

 

 

 

 

 

 


Tue, 03/04/2008 - 20:45

David_N
Posts: 7
 Joined: 2008-02-07

Thanks for the heads up!

As I'm planning to retire to the live aboard lifestyle in a few years, with the bulk of my time spent Stateside, I may just re-think passing  on a true historic jem and hang it on a bulkhead, enjoy it and pass it on a little later with your conversions attached.

Many Thanks --

David 


Tue, 03/04/2008 - 22:36

TheWeatherMan
Posts: 23
 Joined: 2007-12-05

Sure thing...one last comment...when my wife drags me to antique shops...I am always amazed at how expensive the barometers are...


Wed, 03/05/2008 - 08:27

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