1. Air Pressure and Wind Warming air molecules causes them to move faster and spread out. This causes air pressure to change. Air molecules in cold air exert more pressure than warm air because the molecules are close together and collide more often. When denser (heavier) air moves toward less dense (lighter) air, it creates wind. Warm air rises because it is less dense (lighter). Rising air is an updraft, while sinking air is a downdraft. Rising warm air and sinking cool air form a circular pattern of wind called a convection cell. These form because of unequal heating and cooling of the air.

2. Air Pressure and Wind A sea breeze comes from the water and blows toward the land during the day. A land breeze comes from the land and blows toward the water at night. Global wind zones – Polar Easterlies (near the Poles) – Prevailing Westerlies (United States) – Tradewinds (near the Equator) The prevailing westerlies move the weather patterns across the US.

3. Global Wind Zones