How do I convert from kPa to hPa and how do these relate to millibars and inches of Hg?
The Systems International unit for pressure is the the Pascal (Pa) (which is one Newton per square metre). The pressure at mean sea level is about 100000 Pa. To make atmospheric pressure into a number that is more convenient to work with, it is usually quoted in 100s of Pascal. The prefix h stands for hecta, or 100. Thus 1000 hPa is 1000 times 100 Pa or 100000 Pa. The prefix k stands for kilo, or 1000. Other prefixes are shown in this table. Therefore, 1 kPa equals 1000 Pa, or 10 times 100 Pa – which equals 10 times 1 hPa. Thus 1 kPa equals 10 hPa. To convert kPa to hPa multiply by 10. One millibar equals one hPa. In a standard atmosphere mean sea level pressure is 1013.25 hPa or 29.92 inches of mercury. Therefore one inch of mercury is about 33.87 hPa. A useful summary of units, prefixes, conversion factors, constants, etc. can be found at http://nwoca7.nwoca.ohio.gov:70/0gopher_root%3a[_reference]_isou.
