Chapter 5 Lesson 3Global Patterns

Pgs. 164 – 169

Benchmark: SC.6.E.7.3

Vocabulary* tropical zone * leeward

* polar zone * jet stream

* temperate zone * monsoon

* windward

How Do Global Patterns Affect Local Weather?

No matter where you live, the weather changes everyday. The change can be a one-degree change in temperature from one day to the next OR rainy one day and warm and sunny the next day.

4 Patterns That Affect Temperature

1. Latitude: (distance from the equator) areas near the equator are warmer, areas near the poles are cooler.

2. Altitude: (elevation above sea level) the higher you go in altitude, the temperature gets colder. Temperature decreases about 6.5°C for every 1 kilometer increase in altitude.

Patterns That Affect Temperature (continued)

3. Distance from large bodies of water: water heats up and cools down more slowly than land. Therefore, winds off the ocean often prevent extremes of hot and cold in coastal regions. The west coasts of North America, South America, & Europe have mild winters and cool summers. The centers of North America and Asia are too far inland to be warmed or cooled by the ocean.

4. Ocean Currents: areas along the coasts are influenced by ocean currents. Warm ocean currents warms the air above it, the warmed air moves over nearby land, affecting weather patterns. The best-known warm-water current is the Gulf Stream. Cold currents bring cold water from the polar zones towards the equator. A cold current brings cool air.

Based on Latitude, Earth’s surface can be divided into 3 temperature zones:

1. Tropical zone: near the equator, between 23.5°N and 23.5°S latitude, gets direct or nearly direct sunlight all year, so this area is warm.

2. Polar zone: near the poles, from about 66.5° to 90°N and 66.5° to 90°S latitudes, the sun’s rays strike at a lower angle, making these areas cold.

3. Temperate zone: between the tropical and polar zones, temperature here ranges from warm in the summer to cool in the winter.

4 Patterns That Affect Precipitation

1. Prevailing winds: (winds that blow in one direction in a region) These winds move air masses around. Air masses can be warm or cool, OR dry or wet. Winds that blow inland FROM water carry more water vapor (wet). Winds that blow from over land will have less water vapor (drier).

2. Mountain ranges: a mountain range in the path of a prevailing wind can influence where precipitation falls. Humid winds from the ocean toward a coastal mountain is forced to rise, the rising air cools, condenses and forms clouds. Rain or snow falls on the windward side of the mountain (side the wind hits). By the time the air has moved over the mountains, it loses its water vapor. Land on the leeward side of the mountain (downwind) would get little precipitation.

4 Patterns That Affect Precipitation(continued)

3. Jet streams: (narrow bands of high-speed winds 10-15 km above Earth’s surface) they blow west to east & occur along the boundary of warm and cold air masses. Jet streams contribute to worldwide weather patterns and help meteorologists forecast the weather based on their positions.

4 Patterns That Affect Precipitation(continued)

4. Seasonal Winds: In parts of the world, a seasonal change in wind patterns can affect seasonal rainfall. In the summer wind blows inland from the ocean and is warm and humid. This humid air rises over land and cools. The cooling air condenses into clouds and can produce heavy rains. In the winter, wind blows from the land to the ocean. These winds carry little moisture.