Weather and Climate

Chapter 2Weather Factors

Section 3 Key Terms• Wind—

The horizontal movement of air from an area of high pressure to an area of lower pressure.

• Anemometer— An instrument used to measure wind speed.

• Wind-chill factor— Increased cooling caused by the wind.

Section 3 Key Terms (con’t)• Local winds—

Winds that blow over short distances.• Global winds—

Winds that blow steadily from specific directions over long distances.

• Coriolis Effect— The way Earth’s rotation makes winds in the Northern hemisphere curve to the right and winds in the southern hemisphere curve to the left.

• Jet Streams— Bands of high-speed winds about 10 kilometers above Earth’s surface.

Objective

The students will explain what causes winds and describe

major wind belts and where they are

located.

What Causes Wind?• Brain Pop- Wind• Wind is the horizontal

movement of air. The air always moves from an area of high pressure to an area of lower pressure.

• Differences in air pressure are caused by differences in how places are heated by the sun. Warm air has less pressure than cooler air.

What Causes Wind?

Measuring Wind• The name of a wind tells you where

the wind is coming from. For example, a west wind blows from the west.

• Wind speed is measured with an anemometer.

• Wind direction is measured with a wind vane.

Types of Winds• Local winds are winds that

blow over a short distance. A cool breeze blowing from the water over a beach is an example of a local wind.

• A global wind is a wind that blows steadily over long distances. A global wind blows from the same directions every time.

Global Wind Belts• Earth rotates from east to west.

Earth’s rotation makes global winds curve. The way that winds curve is called the Coriolis effect. The Coriolis effect makes winds in the Northern hemisphere curve to the right. It makes winds in the Southern hemisphere curve to the left.

Global Wind Belts

• A series of wind belts circles the earth. Between the wind belts are calm areas.

Wind Belts

Global Wind Belts

High-speed winds called jet streams blow at the top of the troposphere.

Jet streams

Sections 4 & 5 Key Terms• Humidity—

A measure of the amount of water vapor in the air.

• Relative humidity— The percentage of water vapor in the air compared to the maximum amount the air could hold at that temperature.

• Dew point— The temperature at which condensation begins.

• Psychrometer— An instrument used to measure relative humidity, consisting of a wet-bulb thermometer and a dry-bulb thermometer; also known as a hygrometer.

• Rain gauge— An instrument used to measure the amount of precipitation, consisting of an open-ended can topped by a collecting funnel and having a collecting tube and measuring scale inside.

ObjectiveThe students will

describe how relative humidity is measured and name the three

main types of clouds.

Water in the Atmosphere• The water cycle is the

movement of water between the atmosphere and Earth’s surface. During the water cycle, water enters the air through evaporation. Evaporation is when a liquid becomes a gas.

• Humidity is the measure of how much water vapor is in the air. Warm air can hold more water vapor than cold air.

Water in the Atmosphere• Relative humidity is a percentage

measurement. Relative humidity is the percentage of water vapor in the air compared to how much humidity the air can hold.

Measuring Humidity A psychrometer, or

hygrometer, is an instrument that measures relative humidity. A psychrometer has two thermometers. One thermometer has a wet cloth covering it. You can tell the relative humidity of the air by comparing the temperatures on the two thermometers.

How Clouds Form Condensation is when a gas

becomes a liquid. When this happens in the atmosphere, clouds form. For clouds to form, there must be cooling in the atmosphere and particles in the air.

Cold air holds less water vapor than warm air. When air cools, water vapor condenses into little drops of water or ice crystals. The temperature at which this happens is called the dew point.

Types of Clouds There are three main types of clouds:

cirrus, cumulus, and stratus. Cirrus clouds are wispy clouds that form high in the sky. Cumulus clouds look like fluffy piles of cotton. Cumulus clouds can produce thunderstorms. Thunderstorm clouds are called cumulonimbus clouds. Stratus clouds are flat layers of clouds. Stratus clouds usually cover most of the sky. Stratus clouds that produce rain are called nimbostratus clouds.

Clouds that form near the ground are called fog. Fog often forms when the ground cools at night. Fog is common near bodies of water.

ObjectiveThe students will identify

the main types of precipitation and

describe how they are measured.

Types of Precipitation

• Precipitation is any form of water that falls from clouds and reaches Earth’s surface. Types of precipitation include rain, snow, sleet, hail, and drizzle. The types of precipitation are classified by their size and how they form and reach the surface of Earth.

Measuring Precipitation• Snow can be measured with a

measuring stick. It can also be measured by melting the snow and measuring how much water there is.

• Rain is measured with a rain gauge.

Making Clouds• To make a cirrus cloud, take one fourth

of a cotton ball and pull it apart into feather-like pieces.

• To make a stratus cloud, take the rest of that cotton ball and pull it apart slightly into a flat piece.

• To make a cumulus cloud, take 2 cotton balls. Pull them apart slightly to make them puffy.

• Now that you’ve made each type of cloud, sort the characteristics of each type of cloud and write them next to your cloud sample.

Making Clouds

Color Shape/Physical Description Weather

White • look like big puffy cotton balls• flat at the bottom with lumpy tops• often have a popcorn-like appearance

• indicate fair weather, but can get very tall and turn into a thunderhead that brings thunderstorms

White • long, thin, wispy streamers• thin appearance is because they are very high in the sky• made of ice crystals

• usually means fair weather, but can be a sign of approaching weather systems and air disturbances

Grey • form layers with no distinct edges; look like flat sheets of clouds• create overcast blankets• flat and straight• low clouds that cover the sky

• create overcast skies and often bring rain

Making Clouds Cloud Type

Color Shape/Physical Description Weather

Cumulus White • look like big puffy cotton balls• flat at the bottom with lumpy tops• often have a popcorn-like appearance

• indicate fair weather, but can get very tall and turn into a thunderhead that brings thunderstorms

Cirrus White • long, thin, wispy streamers• thin appearance is because they are very high in the sky• made of ice crystals

• usually means fair weather, but can be a sign of approaching weather systems and air disturbances

Stratus Grey • form layers with no distinct edges; look like flat sheets of clouds• create overcast blankets• flat and straight• low clouds that cover the sky

• create overcast skies and often bring rain

Brain Pop•As you watch the video, answer the questions on the worksheet!

•Humidity