Chapter 7 Weather and Climate
*Describe what weather is, what affects it, and where it occurs. *Explain the connection between air pressure and wind. *
*Many factors affect a region s weather. *
*atmosphere - The layer of gases that surround Earth. *troposphere - The layer of the atmosphere closest to the surface *insolation - The amount of the Sun s energy that reaches earth at a given time or place. *
*air pressure - The force exerted on a given area by the weight of the air above it. *convection cell - A circular pattern of rising air, sinking air, and winds. *sea breeze - Wind that blows from sea to land.
*land breeze - Wind that blows from land to sea. *Coriolis effect - The shift in winds to the right or left caused by Earth s rotation.
*As you climb a high mountain, the air gets colder. *This change in temperature would occur because you were traveling upward through the atmosphere, the layers of gases that surround Earth. *The atmosphere extends about 700 kilometers high. *
*The layer of the atmosphere closest to Earth s surface is the troposphere; this is where most of our weather occurs. *The troposphere is about 11 kilometers (7 miles) thick and contains about 80 percent of the total amount of air in the atmosphere. *Air is mainly a mixture of gases, dusts, and water vapor.
*Jet airplanes normally fly within the stable stratosphere; the stratosphere contains the ozone layer, which absorbs the harmful rays from the Sun. *Rock fragments from space sometimes burn up in the next layer, the mesosphere, where the coldest temperatures are found. *The outermost layer the thermosphere, is where space shuttles orbit.
Weather is the state of Earth s troposphere at a given time and place. Weather variables which include temperature, wind, moisture, cloud cover, and precipitation can change periodically. *
*People have always tried to predict weather. *The ancient Egyptians relied mainly on stars so they would know when the Nile River would flood.
Scientists can obtain data by using weather balloons which get readings while going through the atmosphere, weather satellites which provide information from space, and Doppler radar can show an area s current weather, including precipitation, wind direction, and wind speed.
Fact and Opinion Oxygen is the most important gas in the troposphere, because people need it to breath. Is this a fact or an opinion? Explain. This statement is an opinion because we need all of the gases equally. They all support our and other living organisms life functions. *
Critical Thinking Why is it important to be able to predict the weather accurately? How to dress appropriately, whether food must be gathered in advanced, when to plant or harvest crops, and to know when to build shelter.
*In February it might be hot in Argentina and cold in Michigan because as the sunlight reaches the Earth, the Sun s energy penetrates the atmosphere at different angles and warms Earth s surface. *As the surface is warmed it also warms the air above it. *
*The angle of insolation is the angle at which sunlight hits Earth s surface. *As the angle of insolation increases, the air becomes warmer. *The greater the angle, the more intense the Sun s rays. *The rays are the most intense when the Sun is directly overhead.
*The angle of insolation depends on several factors: latitude, time of year, and time of day. *The angle is greater near the equator and smaller near the poles. *The Sun s rays are less concentrated and more spread out near the poles, so they do not warm the surface there as much.
*Because Earth is on a tilted axis, seasonal differences affect insolation. *In the summers of the Northern Hemisphere, the Sun s rays hit Earth at steeper angles than it does for the winter.
*Insolation also varies during the course of the day. *At dawn, the Sun appears close to the horizon, and the angle of insolation is small. *By midday, the Sun appears much higher in the sky, and the angle of insolation is the greatest. *At dusk, the angle of insolation is small once again.
*You can measure the angle of insolation by the shadows it casts. *The shorter the shadow, the steeper the angle of insolation.
*We use three different scales, the Fahrenheit scale, the metric Celsius scale, and the Kelvin scale. *The Kelvin scale does not have any negative numbers. *Water freezes at 32 0 F, 0 0 C, or 273 K. Water boils at 212 0 F, 100 0 C, or 373 K. *An average room temperature is about 72 0 F, 22 0 C, or 295 K. *
Fact and Opinion Solar energy enters the atmosphere and warms Earth s surface and the air above it. Is this a fact or an opinion? This is a fact, based on evidence. The Sun s energy s warming of Earth is not an opinion. *
Critical Thinking Why does the angle of insolation change between midday and evening, and how does this affect the air temperature? The angle of insolation decreases because of Earth s rotation, and the air temperature usually decreases.
*Leaves scatter in the wind because the force of the impact of the air particles is what pushes the leaves. *Air particles still move even if it is not a windy day. *Air particles have mass so Earth s gravity attracts them. *Standard air pressure or the air pressure at sea level is about 1 kilogram per square centimeter. *
*A balloon that is filled has expanded until the air pressure inside the balloon is higher than the air pressure outside the balloon. *When you release the balloon the higher pressure air can escape, reducing the pressure inside the balloon. *When air flows out of the balloon, moving from an area of high air pressure to an area with low air pressure it is called wind.
Earth s air pressure varies; the higher you go - the less air pressure. This happens because there aren t as many air particles being pulled toward Earth by gravity. Air pressure variations help produce wind.
As air warms it spreads out and takes up a larger area resulting in less air in a given volume. The air is then less dense and its pressure decreases. Warmer air with lower density and pressure rises above cooler air.
If a nearby place is warmer and at a lower pressure, air will move from the high-pressure area to a lowpressure area. This is called surface wind. Unequal heating and cooling of a region s air forms a convection cell. *
During the day the wind blows from the water to the land, a sea breeze; at night the wind usually reverses, going from the land to the sea, a land breeze. During the day, air expands over the land faster than air over water, and the cold air blows towards land. *
Weather maps, such as a station model, are used to display wind speed and direction. *
Anemometer is a device that has cups on it, it measures wind speed. A weather vane is a device that measures the wind s direction; the arrow points in the direction the wind blows.
*Barometer measures the surrounding air pressure. *The old barometers measured the air pressure in millibars, the air s ability to maintain the height of a column of mercury.
Fact and Opinion "Land breezes are more refreshing than sea breezes." Is this statement a fact or opinion? Explain your answer. This statement is an opinion. It is based on one s preference, not on facts. *
Critical Thinking What role do changing air temperatures play in a convection cell? In a convection cell, warm air rises and is replaced by surrounding cooler air. As the warm air cools, it sinks, and completes the cycle.
*Winds blow from areas of higher pressure to areas of low pressure. *However, Earth s rotation pushes the winds to either the right or the left; this is called the Coriolis effect. *
*The Coriolis effect causes winds in the Northern Hemisphere to curve to the right, or clockwise. *In the Southern Hemisphere, the winds curve to the left, or counterclockwise.
*Global winds are sometimes called prevailing winds. *The Coriolis effect causes these winds to curve. *Trade winds, the winds that blow toward the equator, are curved to the west by the Coriolis effect. *
*The winds that blow towards the poles curve to the east. *They are called westerlies. *These winds are referred to by the direction from which they come.
Fact and Opinion The Coriolis effect causes winds to curve to the right or the left. Is this statement a fact or an opinion? Explain your answer. It is a fact, based on verifiable evidence. Earth s rotation pushes the winds to either the right or the left, this shift is called Coriolis effect. *
Critical Thinking What causes global wind patterns? Convection currents set air into constant motion, producing global winds due to the Earth s rotation.