World Geography Ch. 3 Sections 1-3 Factors Affecting Climate Weather Factors The most diverse Ecosystems are found in tropical climates. Why? Definitions Weather- the condition of the atmosphere at a given time and place (right now) Climate- weather conditions in a geographic region over a long time (pattern over time) Greenhouse effect- process of the Earths atmosphere trapping heat energy Global warming- Earth has gotten warmer in recent decades The Sun The sun plays a major role in Earths weather and climate Tilt of the Earth is what causes the seasons When the energy of the sun reaches the earth, half of it is reflected back into space or absorbed by the atmosphere Earths surface absorbs the other half, and converts it into heat Understanding Check How does Earths atmosphere help keep the planet warm? Atmospheric Pressure The higher you get in the atmosphere, the pressure becomes less and less because there is less air above you pushing down Air in our atmosphere has weight, even though we dont usually notice it Mountain climbers Air planes Air pressure When air is heated it expands, becomes less dense, and rises This creates a low-pressure area Air cools as it rises, causing water vapor to form clouds Low pressure usually accompanies storms All centers of low pressure are called cyclones Some are just slight breezes, while others are high powered storms Air Pressure Cold air is dense and sinks towards the surface of Earth This creates high-pressure areas Centers of high pressure usually bring clear, dry weather They can also bring extreme heat or cold Pressure Zones Globally there are 4 major pressure zones Equatorial low- direct rays of the Sun cause warm air to rise at the equator. Subtropical highs- The rising air cools and flows towards the poles, it sinks to the surface. Polar highs- Dense cold air sinks to the surface at the poles Subpolar lows- the cold air flows along the surface away from the poles, forces warmer air higher Global Wind Belts Air pressure creates wind Wind- is the horizontal flow of air Hot air rises, then cools, as it sinks back down it displaces air which causes wind. Prevailing winds- winds that blow from the same direction most of the time Doldrums- zone along the equator that is calm with no prevailing winds Prevailing winds Trade winds- blow from the northeast and southeast toward the equator Westerlies- in the middle latitudes, flow from the west Most of the US is located in the westerlies Easterlies- High latitudes, more variable. Blow from the Arctic and Antarctic areas into the middle latitudes In the US, only Alaska is far enough North to be in this wind zone Front A front occurs when two air masses of widely different temperatures or moisture levels meet Oceans and Currents Water heats and cools more slowly than land Wind and varying ocean temperatures create ocean currents Currents flow in circular paths They move clockwise in the Northern Hemisphere and counter- clockwise in the Southern Hemisphere The oceans affect Earths climate by pulling the suns energy along certain paths. ex.) England should be chilly but is affected by the same Gulf Stream that keeps us hot and humid. Gulf Stream The ocean stores heat and affects the temp. of the atmosphere and its circulation. Humidity The amount of water vapor in the air is called humidity The higher the temperature, the more water vapor the air can hold Elevation and Mountain effects High elevation affects weather and climate Increase in elevation causes a drop in temperature Orographic effect- occurs when moist air pushes against a mountain The barrier forces the air to rise, cooling and condensing as it goes Forms clouds and causes precipitation on the windward side The opposite side is called the leeward side (away from the wind) As the air moves down the leeward side it dries and warms forming a rain shadow Storms- Middle Latitudes Hurricanes are measured by atmospheric pressure. The lower the pressure, the stronger the storm. Sudden, violent weather events High winds, flooding, blowing snow, lightning, turbulent seas Storms usually move from west to east in the middle latitudes, pushed by the jet stream flow (winds) Called extra-tropical cyclones Thunderstorms Tornadoes Storms- tropics Usually much smaller Lack fronts, because there is no cold air present Travel westward Hurricanes are the most powerful tropical cyclones AKA typhoons in the western Pacific Factors that make hurricanes strengthen are warm water and drop in atmospheric pressure. In order: tropical wave, tropical depression, tropical storm, categories 1-5. Assignment Chapter Review pg Do the following: Locating Places A-G (pg ) Understanding Main Ideas # 1-5 Thinking Critically#2-3 Interpreting Maps # 1-2 Conclusion The sun plays a huge role in weather and climate here on Earth Weather and climate affect our daily lives, so it is important to understand them before we study different groups of people around the world Assignment: Chapter 3 Map Activity WS Climate and Vegetation Ch. 3.3 Climate Regions Climate regions tell geographers about an area without giving many local details. Temperature and precipitation are the two most important factors. 5 General Regions: Tropical (low latitude), dry (arid), mid- latitude, high latitude, and highland. Tropical Wet Always hot Avg. temp. of 80 deg. F Central & South America Africa and Southwest Asia Humid Subtropical Long, hot and humid summers Mild to cool winters Found on east coast of continents Suitable or raising crops Mediterranean Summers are hot and dry Winters are cool and wet Marine West Coast Moderate temperatures frequently cloudy, foggy, damp Semiarid Receives little precipitation Hot summers Found in interior of continents, near deserts Desert Categorized according to rainfall Can be hot or cold Receive less than 10 inches of rain/year Tundra Flat, treeless lands around Arctic Circle Very little precipitation Mostly in Northern Hemisphere Permafrost subsoil always frozen Ice Cap Permanently freezing Rarely snows too cold Called polar deserts Soils and Vegetation Soil and climate help to determine the vegetation of a region. Human land use alters the vegetation in both positive and negative ways. Shaping Human Existence Soil is a thin layer of weathered rock, humus, air, water Topsoil refers to the top 6 of soil Soil characteristics vary with climate Type of soil determines type of vegetation that can be supported Type of vegetation determines type of possible human activity. Natural Environments Ecosysteminterdependent community of plants and animals Biomethe ecosystem of a particular region Biomes are further divided into: - forest - grassland - desert - tundra Forests Forest regions categorized by trees they supportbroadleaf or needle Deciduousbroadleaf trees: maple, oak, birch, cottonwood - mostly in Northern Hemisphere Coniferousneedle leaf trees; cone bearing: pine, fir, cedar - mostly in Northern Hemisphere Deciduous and coniferous trees together form mixed forest Which type of Forest? Forests Rain foresttropical forest covered with broadleaf trees Grasslands Flat regions with few trees A savanna is a tropical grassland Steppe, or prairie, are temperate grasslands of Northern Hemisphere Desert and Tundra Plants in these regions have adapted to climate extremes: - tundra plants (mosses, lichen) hug the ground - desert plants (cacti, sagebrush) conserve water, withstand heat Human Impact on the Environment Humans either adapt to land, or alter it to meet their needs Some human activities that affect the environment: - building dams - installing irrigation systems - planting crops - slashing and burning vegetation Conclusion 5 General Regions: Tropical (low latitude), dry (arid), mid- latitude, high latitude, and highland. Assignment: Main Idea 3.3 WS