20.4 Weather Maps

20.4.2 Identify the following features found on surface weather maps:

20.4.4 Explain the most common weather characteristics of each feature.

(a) isobars;

Isobars are lines on a weather map, connecting points of equal atmospheric pressure.

(b) anticyclone (“high”);

In the Southern Hemisphere, an anticyclone is an anticlockwise circulation of winds around a central region of high atmospheric pressure,

• It has higher pressure at its center than the areas around it.
• Air sinks down.
• The winds blow away from high pressure.
• A blue H denotes the location of a high pressure system.
• characterised by fine weather with light winds

(c) depression (“low” or “cyclone”);

In the Southern Hemisphere, a depression is a clockwise circulation of winds around a central region of low atmospheric pressure.

• It has lower pressure at its center than the areas around it.
• Air rises up.
• winds blow toward the low pressure.
• a red L denotes the location of a Low pressure system.
• characterised by poor weather and strong winds

(d) ridge of high pressure;

• A ridge is an extension of a high.
• similar conditions to a high