The Water Cycle and Weather
Chapter 7 lessons 3-5
What is weather?
Lesson 3
Weather is the state of the atmosphere, including temperature, wind speed and direction, air pressure, moisture, amount of rain or snow.
Meteorologists study and predict the weather. They collect data from tools to tell about the weather today and to predict future weather.
Gravity pulls the mass of air in the atmosphere toward the Earth’s surface.
Barometric Pressure is the pushing force of the atmosphere.
Over ¾ of Earth’s atmosphere is nitrogen, the rest is mostly oxygen mixed with small amounts of carbon dioxide.
Air Temperature affects weather. As warm air rises an area of low pressure forms and air from the areas with higher pressure rushes in.
As air cools the particles in the air become more closely packed causing the air to become denser.
Wind is air movement caused by differences in pressure.Airmoves from areas of high pressure to areas of low pressure.
Wind speed and direction affect weather. Weather can be affected by special winds called jet streams. These affect day to day weather and seasons. Jet Streams are narrow bands of high speed wind.
Humidity is the amount of water vapor in the air. The particles of water vapor are too small to be visible, but when conditions are just right, they can come together to form small water droplets and ice crystals. These droplets and crystals are bigger than water vapor particles. If these droplets or crystals get large enough, they can fall to the ground as precipitation, snow, or rain.
Wind follows different patterns due to temperature and pressure.
Circulation is the movement of air that redistributes heat on Earth.
How Do Clouds and Precipitation Form?
Lesson 4
Precipitation forms when gravitational forces cause large particles formed by ice crystals and water droplets to fall out of the cloud.
Clouds form when water vapor changes into tiny water droplets or ice crystals. Clouds are important because they are part of the water cycle; they move water to other places on Earth.
Sleet is frozen rain drops.
Clouds of ice crystals form in cold air. The ice crystals grow larger until they start to fall as snowflakes. If the temperature of all the air between the clouds and the ground is less than 0 degrees Celsius, the ice crystals will fall to the ground as snowflakes.
Strong winds blow upward through a thunderstorm cloud. These winds blow raindrops back up into the freezing air. This creates a small piece of ice. As ice is blown through the cloud many times, many layers of water freeze on it. It gets too heavy for the winds to carry it back up. This frozen precipitation that forms in layers is called hail.
Types of clouds: Cirrus, Cumulonimbus, Altocumulus, Stratus, Fog
What is climate?
Lesson 5
Climate describes the weather conditions over a long time. Climate does not change as much as daily weather does. Factors that affect climate are latitude, elevation, and closeness to bodies of water.
Latitude is the measure of how far a place is from the equator. It is measured in degrees, and begins at 0 degrees which is the equator. An area nearer to the equator is usually hotter than places farther away.
Bodies of Water
The ocean can affect a climate by slowing the rise and fall of air temperature. Bodies of water become warm and cool more slowly than land. So, the temperature of the air near the water does not change as quickly as inland.
Elevation
Mountain ranges have different climates than areas around them. Higher land is cooler because in the lower part of the atmosphere temperature decreases with increased elevation. Elevation is the height above sea level.