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2.2 Wind Notes Quarter 1 Weather The condition of Earth’s atmosphere at a particular time and place. Wind plays an important role in weather. Wind Air that moves horizontally, or parallel to the ground. Caused by differences in pressure. Moves from high to low pressure over short distances. Air circulation caused by uneven heating of Earth’s surface: 1. Sunlight heats an area of the ground. The ground heats the air. The warm air rises, and an area of low pressure forms. 2. Sunlight heats an area of the ground less strongly. The cooler, dense air sinks slowly, and an area of high pressure forms. 3. Air moves as wind across the surface, from higher toward lower pressure. Global Winds Travel thousands of kilometers in steady patterns and can last for weeks. Caused by uneven heating between the equator and the north and south poles. Sinking dense air causes high pressure setting global winds in motion. Coriolis Effect Since the Earth rotates, the direction of winds curve with the rotation. Northern hemisphere: curve to the right in the direction of motion (SW) Southern hemisphere: curve to the left in the direction of motion (NW) A circulation cell is a giant loop of moving air that includes a wind belt and the calm regions that border it. Global Winds 1. 2. 3. 1 4. 2 3 4 5 5. Air rises in the doldrums, a low pressure zone. Air sinks in the horse latitudes, a high pressure zone. The trade winds blow from the horse latitudes toward the equator. The westerlies blow from the horse latitudes toward the poles. The easterlies blow away from the polar regions. Calm Regions Doldrums Low pressure area near equator Clouds and heavy rain Horse Latitudes High pressure area above 30 degrees north and south of equator Clear and dry Wind Belts Three types: Trade winds – come from East moving toward the equator, strong and steady winds gradually die out Westerlies – come from West moving toward the poles, bring storms Easterlies – come from East moving from poles to mid-latitudes, stormy weather when they meet up with the Westerlies Jet Streams In the upper troposphere Travel in a wavy pattern from west to east for thousands of kilometers Form because of uneven heating of Earth’s surface Affect air travel times Local Winds Sea breeze: Warmer air rises over land during the day. Cooler air blows in from the water. Land breeze: Cooler air blows out from land. Warmer air rises over water at night. Monsoons Winds that change direction with the seasons. Caused by different heating and cooling rates of land and sea. Winter Monsoon vs. Summer Monsoon Moist air blows from the high-pressure areas over the ocean to the low pressure area over the continent. Brings much rain to the land. Dry air blows from the high-pressure area over the continent to the low pressure areas over the ocean.