Good show with about the comments about the use of millibars by the Weather Channel. The NOAA National Weather Service and the American Meteorological Society have converted to hectopascals. However, they use millibars in severe storm warnings since that is what the public and most amateur weather people have on their pressure instruments. Kilopascals would be a much better unit to use for weather.
As you know, millibars is metric and is equal to hectopascals which is another name. Millibars has been used for a century. Compatibility with other uses of pressure was not a consideration when weather people chose hectopascals.
Stan Doore
Dear Stan,
I just checked my copy of ‘The International System of Units’ (7th edition BIPM 1998) to check where the bar appeared in the ‘Metric Bible’.
It is listed under:
Table 8. Other non-SI units currently accepted for use with the International System
Does inclusion of the bar in this list make it appropriate to say, ‘millibars is metric’?
I suspect that you are right when you say ‘millibars is metric’ for historical reasons, but I maintain that millibars are not SI units in that they are no longer listed as an SI unit.
The bar is ‘metric’ for the historical reason that it was included in Resolution 7 of the 9th CGPM in 1948, but it is no longer an SI unit as it is only recognised as one of the ‘Other non-SI units currently accepted for use with the International System’.
Cheers,
Pat Naughtin ASM (NSAA), LCAMS (USMA)*
PO Box 305, Belmont, Geelong, Australia
Phone 61 3 5241 2008
Pat Naughtin is the editor of the free online monthly newsletter, 'Metrication matters'.
You can subscribe by going to http://www.metricationmatters.com/newsletter
* Pat is the editor of the 'Numbers and measurement' chapter of the Australian Government Publishing Service 'Style manual – for writers, editors and printers', he is an Accredited Speaking Member (ASM) with the National Speakers Association of Australia, and a Lifetime Certified Advanced Metrication Specialist (LCAMS) with the United States Metric Association. For more information go to: http://metricationmatters.com
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