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WEATHER 71% of the earth is water. Water Dispersal on Earth The mass of air that surrounds the earth is the atmosphere. Water is found in the atmosphere in the form of rain, snow, hail, sleet, water vapor and the water droplets that make up clouds. All these gases are held in the atmosphere by the earth’s gravitational pull. There are five layers to the earth’s atmosphere •troposphere •stratosphere •mesosphere •thermosphere •exosphere The troposphere is between 0-7 miles from earth’s surface and contains clouds, weather, water and dust particles, flying animals, and commercial air traffic. The stratosphere is 730 miles from earth, is 40 degrees, and contains the ozone layer and fighter planes. The mesosphere is at 3050 miles. It is the coldest part of the atmosphere (at –90 degrees) and only large helium balloons fly there. The thermosphere is located 50-300 miles from earth and is the hottest layer (930-3,000 degrees). Satellites, Sputnik, and the X-15 can go there. The exosphere is any area in space over 300 miles from earth. There are no atmospheric gases from earth in this layer.The shuttle and other space ship can go there. About halfway through the thermosphere at 180 miles, the atmosphere merges with the thin gases of interplanetary space. Weather is the condition of the lowest layer of the atmosphere at a particular time and place. We experience weather in precipitation, wind, temperature, and humidity. The Coriolis effect is the way the winds swirl around the earth because of its rotation. This circulation of air is mainly responsible for the weather conditions around the world. Nuclear fallout from the Chernobyl nuclear incident spread throughout Europe You can see how the volcanic ash spread from Alaska to Canada in a three day period. The consistent movement of air in a specific direction over an area is called a jetstream. There are two jetstreams that cover the United States. This causes the air in the United States to consistently move in a certain direction. One jetstream brings cold air from the north. The other brings warmer and moister air from the south. These bands of moving air run from west to east, basically splitting the United States in half. A cloud is a mass of billions of tiny droplets of waters or ice crystals floating above earth. Clouds form when warm, moist air meets cold air. It is only when water droplets repeatedly collide and fuse together into large droplets, that they finally become heavy enough to fall as rain. 3 basic types of clouds •cumulus •stratus •cirrus CUMULUS STRATUS CIRRUS STRATOCUMULUS Some unusual clouds supercell: thunderstorms and tornadoes Contrails are white cloud-like shapes in the sky made by aircraft when moisture from burning fuel meets cold air. air traffic around world FYI The rainiest spot on earth is Mt. Waiaheale, Hawaii. It gets about 471 inches of rain a year. FYI When a city the size of Chicago gets 1 inch of rain, over 4 billion gallons of water fall. Precipitation is any kind of water or ice that falls from the clouds. The water on earth is continually being changed from one form to another. This change in the state of matter of water is called the water cycle. There are 7 steps to the water cycle. Water in lakes and oceans is heated by the sun’s energy and rises into the air (evaporation) In evaporation there is a change of water from a liquid to a gas. The water rises high enough to freeze and form a cloud (condensation) In condensation there is a change of water from a gas to a solid. The water falls from the cloud as rain, sleet, hail, or snow (precipitation) When the water returns to earth, four things can happen: run off accumulation infiltration transpiration run off water that has fallen as rain and has stayed on the surface of the earth. It moves from higher to lower elevations as "runoff“. accumulation water collected in lakes, rivers, streams, oceans, etc. that will evaporate into water vapor Infiltration the flow of water from the ground surface into the ground where it becomes soil moisture or collects as groundwater. (water stored beneath the earth's surface between saturated soil and rock that supplies wells and springs) Transpiration water given off as microscopic water vapor from the bottom of plant leaves FYI The largest hailstone on record weighed 1.7 pounds and measured 17.5 inches in circumference. It fell in 1970 in Coffeyville, Kansas. FYI In June 1932, a hailstorm in China killed 200 people and injured thousands more. In areas of high pollution, dirt particles contain chemicals. When they attach to the water droplets in the cloud and fall to earth, they are called acid rain. There are over 100 lightning strikes on earth every second. In North America alone, about 400 people a year are struck by lightning, a quarter of them fatally. Lightning is caused by electrical currents that pass between a cloud and the ground. FYI A flash of lightning can sometimes be over 5 miles long. FYI Lightning temperatures can reach over 50,000 degrees F. THAT’S 5 TIMES HOTTER THAN THE SUN’S SURFACE. FYI More people are killed by lightning each year than by hurricanes, blizzards, or tornadoes. typical marks from a lightning strike Forest fires are frequently caused by lightning strikes. When lightning is not accompanied by rain, forest fires will quickly spread over a large area. LIGHTNING STEPS 1. clouds have a negative charge 2. ground has a positive charge 3. clouds send their negative charge down 4. ground sends its positive charge up 5. lightning occurs where the two charges meet top of cloud: positive charge bottom of cloud: negative charge When there are more negative than positive charges in the cloud, the extra negative charges go toward the ground Lightning occurs where the positive and negative charges meet Things on the ground have a positive charge. Positive charges are sent into the air. There are three types of lightning: cloud-to-air cloud-to-cloud cloud-to-ground cloud-to-air least powerful caused by too much positive charge in air surrounding cloud CLOUD-TO-AIR LIGHTNING cloud-to-cloud most common type travels within a cloud or from cloud to cloud higher clouds, so too far away to hear thunder CLOUD TO CLOUD LIGHTNING cloud-to-ground negative charge in base travels to positive charge from ground CLOUD-TO-GROUND LIGHTNING Lightning comes in many different colors. lightning colors • red means rain in the cloud • blue means hail in the cloud • yellow is caused by dust • white means low humidity (most forest fires are started by white lightning) Thunder is created because some of the tremendous energy of lightning flashes is turned into heat and then into sound waves. FYI Thunder is heard an average of 242 days a year in Kamal, Uganda. FYI The Empire State Building in New York City is hit by lightning about 42 times a year. A hurricane is a storm in which strong winds whirl around a lowpressure center. A hurricane is made of hundreds of large thunderstorms that spiral around each other. The winds blow at speeds of 100 miles per hour or greater, sometimes reaching 200 miles per hour. They occur in a narrow band between 0 to 30 degrees on either side of the Equator. The reason for this that they require ocean temperatures of at least 80 degrees to form. spinning winds eye of hurricanearea where there is no rain or winds Hurricane-like storms in the Pacific are called typhoons. A tornado, or twister, is a destructive storm with whirling winds. The winds make their way to earth as a spinning funnelshaped cloud. Tornados can occur individually or in large groups, as large as 100 to 150. That conditions that create a tornado involve warm, humid air meeting dry air and cool, humid air. The Fujita Tornado Scale is a scientific classification system to categorize the strength of a tornado. It ranges from 1-5. Most tornadoes only rate 1 on the Fujita scale meaning there is very little damage. Only about 1% of all tornadoes are rated 4-5 on the scale, meaning that they are extremely destructive. The Beaufort Wind Scale classifies a wind’s strength. A water spout is a tornado like structure that develops over the water. Unlike a tornado, a water spout forms from the water to the sky. SAND STORMS Sandstorms occur in desert areas like the Middle East and the Southwestern parts of the U.S. (like Arizona) and are caused by strong winds blowing over loose soil or sand. Dust storm traveling from Egypt to Saudi Arabia Poor visibility for driving and respiratory problems can cause deaths. Climate is the average weather in an area over a long period of time. It is classified based on two factors: amount of precipitation and normal yearly temperatures. Climate is categorized into five systems. Polar climate has permanent snow or ice and only light precipitation. The warmest month is 50 degrees. Humid and cold climates have hot summers and cold winters with a low of 27 degrees and an average rainfall less than 20 inches a year. Warm and rainy climates have mild winters with the coldest month between 27 and 64 degrees. The average yearly rainfall is between 2040 inches. Tropical rain climates average no less than 64 degrees at any time. The average rainfall in a year is 72-180 inches, with 6-15 inches in the rainy season.. Dry climates are areas that average less than 10 inches of rainfall a year. The causes of climate change can be divided into two categories - those that are due to natural causes and those that are created by man. Human Causes Land that was covered with vegetation has been cleared to make way for houses. Natural resources are being used extensively for construction, industries, transport, and consumption. Consumerism: humans are daily creating mountains of waste. Recycling could help greatly reduce the amount of garbage that is collected each year. Population has increased to an incredible extent. All this has contributed to a rise in greenhouse gases in the atmosphere. Greenhouse gases and their sources Deforestation, land clearing, agriculture, and other activities have all led to a rise in the emission of carbon dioxide. Methane is another important greenhouse gas in the atmosphere. About ¼ of all methane emissions are said to come from domesticated animals such as dairy cows, goats, pigs, buffaloes, camels, horses, and sheep. Methane is also released from rice or paddy fields. Methane is also emitted from landfills and other waste dumps. Natural Causes There are a number of natural factors responsible for climate change. Some of the more prominent ones are continental drift, volcanoes, ocean currents, the earth's tilt, and comets and meteorites. Continental Drift Continental drift had an impact on the climate because it changed the physical features of the landmass, their geographic position and the position of water bodies. Volcanoes When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapor, dust, and ash into the atmosphere. The large volumes of gases and ash can influence climatic patterns for years. The gases and dust particles partially block the incoming rays of the sun, leading to cooling. The Earth’s Tilt Changes in the tilt of the earth can affect the severity of the seasons - more tilt means warmer summers and colder winters; less tilt means cooler summers and milder winters. Elevation is the distance above sea level. As you go higher up a mountain, the air pressure decreases and the gas molecules spread farther and farther apart and hold less heat, so it becomes colder. Latitude determines the amount of solar energy received by that region. Regions close to the equator receive direct rays of the sun and therefore receive more of the sun’s heat and are warmer. At the areas closer to the poles, the sun’s rays are at an angle so these areas receive less sun’s heat and are cooler. Water, like air, moves around the earth as warm or cold winds and currents. It moves in a cycle from ocean, to air, to land, and back to oceans. Water in the ocean travels in paths called currents. Currents can either be warm or cold. The temperature of the water affects the temperature of the air above it. If the water is cold, it cools the air above it. If it is warm, it heats up the air above it. Ocean currents traveling away from the equator are warm. Currents flowing toward the equator are colder. These cooled air masses then flow over the regions in their path. Much of the heat that escapes from the oceans is in the form of water vapor. Water vapor contributes to the formation of clouds, which shade the surface and have a net cooling effect. It is important to us that the oceans stay healthy. They drive our climate and weather. Oceans provide a livelihood for many millions of people worldwide through fishing, energy and mineral resources, shipping, and leisure activities Oceans pose threats through floods, tsunamis, storms, sea level change and coastal erosion. More than half the world’s population lives near the sea. Most waste eventually ends up in the oceans, with the result that marine pollution is a global problem - every part of every ocean is now affected. The amount of precipitation in a region is affected by mountain ranges in that area. Mountains cause air to rise. Rising air becomes less dense allowing the condensation of water. Precipitation occurs. Winds can greatly affect the amount of precipitation an area receives depending on the amount of moisture they are carrying. These winds can move air masses from the ocean onto a continent bringing moisture onto the continent. Or winds may move air masses from continent to the ocean, moving drier air from the continent. These winds affect the climate of an area. FYI The driest place on earth is Arica, Chile. Its gets only 0.3 inches of rain a year. FYI The hottest place in the world is Dallol, Ethiopia where the average temperature year round is between 95 and 100 degrees F. FYI The “Pole of Cold” in Antarctica is the coldest place on earth. The average temperature is –72 degrees F and down to –130 degrees F in July. Greenhouse Effect The greenhouse effect occurs when carbon dioxide levels in the air build up and hold heat in the earth’s atmosphere. It causes a reduction in the ozone layer and global warming. Scientists measure the temperature at many different locations several times each day to determine how much the earth’s temperature is increasing. We are currently in one of the warmest periods in our earth’s history. Another way we are altering the weather in a dangerous way is by pollution. Chemical pollutants in the air create acid rain and smog. Smog is a kind of manmade weather, a combination of smoke and fog that is darker and heavier than normal fog. Chemicals in the atmosphere open holes in the ozone layer and allow harmful rays to reach earth’s surface. This increase can heat the planet and increase the risk of skin cancer.