What do Hg and Pa mean in weather related terms?
1 Answer
The terms Hg and Pa refer the measures of atmospheric pressure.
Explanation:
Atmospheric pressure is important for describing weather conditions. Weather is caused by the interactions of areas of higher than average air pressure and lower than average air pressure.
Air pressure has been measured using mercury. You fill a thin glass tube with mercury and invert it so that the open end is in a bowl of mercury. The atmosphere can only support a column of mercury of around 760mm. The level of mercury falls to the height the atmospheric pressure can support, leaving a vacuum at the top.
As the symbol for mercury is Hg, atmospheric pressure can be measured in millimetres of mercury or mmHg. As mercury is very toxic it is not used to measure atmospheric pressure, but other units of air pressure can be converted to mmHg.
The other unit of air pressure is the Pascal, abbreviated to Pa.
A standard atmosphere is 101,325 Pa which is the average air pressure at sea level.
