Final answer:
The millibar (mb) is the unit of pressure commonly found on surface weather maps, used by meteorologists to depict subtle changes in atmospheric pressure. Isobars connect areas of equal pressure, indicating regions of high and low weather influence. The average sea level pressure is 1013 millibars.
Step-by-step explanation:
The unit of pressure often found on surface weather maps is the millibar (mb). Since bars represent a relatively large unit of pressure and the changes in surface pressure are usually small, meteorologists use the more sensitive millibar to depict these variations accurately. One millibar is equivalent to 1 x 102 pascals (Pa), which is a more convenient scale for the generally subtle changes in atmospheric pressure that significantly influence weather patterns.
Weather maps utilize isobars, lines that connect points of equal atmospheric pressure, to illustrate areas of high and low pressure. These areas are critical in determining weather conditions. The average atmospheric pressure at sea level is about 1013 millibars, which is also considered 1 atmosphere (atm) or 1.013 bars.