Chapter 18 Climate

Southwest US – hot, dry all year. CLIMATE General conditions of temp & precipitation for an area over a long period of time. Southwest US – hot, dry all year.

Climate of a region is determined by: 1. Temperature 2. Precipitation

FACTORS THAT AFFECT TEMP Latitude- measure of the distance N & S of equator. Closer to equator, more direct sunlight, warmer climate. Farther away from equator, less sunlight, cooler climate.

2. Elevation- as elevation increases, air cools & can’t hold as much moisture so temp decreases.

OCEAN CURRENTS

3. Ocean Currents- a river of water that flows in a definite path in the ocean. The surface temp of water affects the temp of the air.

Warm water currents travel away from equator. Cold water currents travel toward the equator. Land near currents is affected by the temp of the ocean currents.

4. Distances From Water Oceans greatly moderate the temps of nearby land. Water heats/cools slower than land.

FACTORS THAT AFFECT PRECIPITATION Prevailing Winds- Carries different amounts of moisture which affects precipitation.

Winds that blow from sea to land carry more moisture. Places in the center of a land mass have dry climates.

Region that receives less than 25cm of precipitation in one year. DESERT Region that receives less than 25cm of precipitation in one year.

2. MOUNTAIN RANGES Act as barriers to winds Mountains cause air to rise 2 parts of a mountain: windward side & leeward side

A) Windward side- receives a lot of precipitation. Faces the wind A) Windward side- receives a lot of precipitation. Faces the wind. B) Leeward side- drier air. Faces away from wind.

How Mtns. Affect Precip. Air is forced up. As it rises, it starts to cool. Cold air can’t hold as much moisture so precipitation occurs on the windward side. Air that comes over the Mtn. (leeward side) is drier.

3. SEASONAL WINDS Monsoon- a major landbreeze or seabreeze that changes direction with the seasons.

THE SEASONS Most places outside the tropics have 4 seasons: summer, fall, winter, & spring.

Causes of Seasons Tilted Axis- the tilt of the earth’s axis as the earth travels around the sun. Tilted on an angle of 23.5

The north end of the axis is pointed away from the sun for part of the year (Winter)& toward the sun for another part of the year (Summer).

In summer, N. hemisphere is tilted towards the sun = more direct sunlight, warmer temps. (June) In the winter, N. Hemisphere is pointed away from sun = less sunlight, colder temps. (December)

Sec. 2 Climate Regions

CLASSIFICATION Climates are classified according to: 1. Temperature 2. Precipitation

6 Main Climate Regions Tropical rainy Dry Temperate marine Temperate continental Polar Highlands

1. Tropical Rainy Climates Found in low-lying lands near equator. 2 types: Tropical Wet, & Tropical Wet-&-Dry.

Hot/Humid, many rainy days, over 10meters/year. Tropical Wet Hot/Humid, many rainy days, over 10meters/year. Windward side of Hawaii Rain Forest- forests in which large amounts of rain fall year-round.

Hot, receives slightly less rain & has a distinct dry & rainy season. Tropical Wet & Dry Hot, receives slightly less rain & has a distinct dry & rainy season. Savannas- tropical grassland Southern Florida

Arid Climate & Semiarid Climate. 2. Dry Climates A climate is dry if the amount of precipitation that falls is less than the amount that evaporates. Arid Climate & Semiarid Climate.

Desert, with little precipitation (less than 25cm/year). Arid Climate Desert, with little precipitation (less than 25cm/year). Hot, sandy & cold or rocky Parts of California & Southwest.

Dry but receives 25-50cm of precipitation/year. Semiarid Climate Dry but receives 25-50cm of precipitation/year. Steppe- dry region that gets enough rainfall for short grasses & bushes to grow. Great Plains

3. Temperate Marine Climate Along the coasts of temperate continents Humid (50F+) in summer & mild winters (20F to 64F). Mediterranean, Humid Subtropical, Marine West Coast.

Coastal climate that is drier & warmer than West Coast Marine. Mediterranean Coastal climate that is drier & warmer than West Coast Marine. Mild winters, cool summers, & moderate rainfall. (agriculture) Southern California,

Warm, dry summers & rainy winters Marine West Coast Warm, dry summers & rainy winters Northern California to Southern Alaska Because of heavy precipitation, thick forests grow here.

Hot/Humid summers & cool winters. Warm & wet. Southeast US Humid Subtropical Hot/Humid summers & cool winters. Warm & wet. Southeast US Forests, oranges, peaches, sugarcane.

4. Temperate Continental Climate Only found on continents in the Northern Hemisphere. Not influenced by oceans- you get extreme temps. 50F or above to 20F or below

NE United States, Mid West US. Humid Continental Hot, humid summers & cold winters with moderate precipitation year round. NE United States, Mid West US.

Short, cool summers & long, cold winters with light precipitation. Subarctic Short, cool summers & long, cold winters with light precipitation. Eastern Alaska, Canada

Coldest climate, Avg. temps below 50F in warmest month. 5. Polar Climate Coldest climate, Avg. temps below 50F in warmest month. Includes North & South Poles, Icecaps, & tundras.

Stretches from northern Alaska, Canada, & Russia. Tundra Stretches from northern Alaska, Canada, & Russia. Short cool summers, bitterly cold winters.

PERMAFROST Permanently frozen land, water cannot drain away so the soil is wet & boggy in summer. No trees, but moss/grass/shrubs grow.

Cooler & wetter than nearby lowlands. Temp decreases with altitude. 6. Highlands Climate Cooler & wetter than nearby lowlands. Temp decreases with altitude. Short summers, long, severe winters. NW US.

Sec. 3 Long-Term Changes

Studying Climate Changes If plants or animals today need certain conditions to live, then similar plants & animals in the past also required those conditions.

Types of Evidence to Study Climate Changes Fossil evidence Tree rings Pollen

Tree Rings Scientists study the pattern of thick or thin tree rings to tell about warm/cool or wet/dry climate.

Cold periods, Glacial episodes. Ice Ages Cold periods, Glacial episodes. Huge sheets of ice (glaciers) cover large parts of the Earth’s surface.

Last Ice Age was 10,500 yrs ago. Sheets of ice covered N Europe, & North America as low as Indiana & Iowa. A lot of water was frozen causing ocean level to drop.

Movement of Continents CAUSES OF CHANGE Earth’s position Solar energy input Volcanic Activity Movement of Continents

Section 4

Short-Term Climate Changes 1. Ocean Currents- El Nino, La Nina 2. Global Warming 3. Ozone Depletion

Brings severe conditions- rain or drought. El Nino Unusual pattern of warm winds & water that form over the Pacific Ocean & move eastward towards the coast of South America. Brings severe conditions- rain or drought.

Surface waters of eastern Pacific Ocean are colder than usual. La Nina Surface waters of eastern Pacific Ocean are colder than usual. Brings colder winters & greater precipitation to Pacific NW & North Central US. Greater hurricane activity in western Atlantic Ocean.

A gradual increase in temp. of earth’s atmosphere. Greenhouse effect GLOBAL WARMING A gradual increase in temp. of earth’s atmosphere. Greenhouse effect Greenhouse gases: carbon dioxide, methane trap heat. Human activities add greenhouse gases to the environment.

Chlorofluorocarbons (CFC’s) are a major cause for depletion. Ozone Depletion Chlorofluorocarbons (CFC’s) are a major cause for depletion.

CFC’s in air conditioners/aerosol sprays release CFCs into the air & they stay in the atmosphere & breakdown the ozone layer.