mm of mercury
The millimeter of mercury (mmHg) is pressure unit traditionally used in meteorology. It is the pressure from a 1 mm column of mercury at 0°C under normal gravity.
Millibar
The millibar (mb) is commonly used in meteorology. The millibar is a metric unit of pressure equivalent to 100 pascals. Standard Earth atmospheric pressure at sea level is approx 1013.25 millibars.