Which statement about isobars on weather maps is correct?

• A. Isobars indicate line of constant temperature.
• B. Isobars indicate rainfall distribution.
• C. Isobars correspond to the height of the tropopause.
• D. Isobars connect points of equal pressure; spacing reflects wind strength and patterns identify highs and lows.

Answer: (D)

Isobars are lines that connect points of equal atmospheric pressure on a weather map. They show the pressure field at a given level (often sea level pressure). The distance between isobars tells you how strong the pressure gradient is: closely spaced isobars mean a steep gradient and stronger winds, while widely spaced isobars indicate a weaker gradient and lighter winds. Closed isobars around a center identify high and low pressure areas—the center of a low has decreasing pressure toward the middle, while a high centers around increasing pressure.

They don’t indicate temperature (that’s isotherms), they don’t map rainfall directly, and they aren’t lines of tropopause height (which relate to geopotential height at a given pressure level). So the statement that isobars connect points of equal pressure, with spacing reflecting wind strength and the pattern around them identifying highs and lows, is the correct description.