What does an isobar represent on a weather map?

• A. A line on a weather map connecting points of equal atmospheric pressure.
• B. A line indicating equal humidity.
• C. A line showing equal wind speed.
• D. A line representing surface temperature.

Answer: (A)

An isobar is a line that connects all points on a weather map where the atmospheric pressure is the same at a given level, usually sea-level pressure, with the values shown in millibars or hectopascals. This representation reveals pressure patterns: centers of high and low pressure appear where the isobars form closed loops, and how tightly the isobars are spaced indicates the pressure gradient and the likely wind strength—the closer the lines, the stronger the winds, since air moves from high to low pressure to balance the difference. Isobars themselves do not show humidity, wind speed directly, or surface temperature; those properties are shown by other types of lines (like isotachs for wind speed or isotherms for temperature).