Measuring Weather How Does Sunlight Affect Air Temperature? How does Temperature Affect Air Movement? What Causes Clouds and Precipitation? How Do Meteorologists Predict Weather?

Lesson 1: How Does Sunlight Affect Air Temperature? Why is it cooler at night than in the afternoon? It is because the temperature of the air has to do with how much sunlight, or light energy from the sun, reaches the earth. Sunlight passes through the air but does not heat it. Rather, light energy from the sun hits liquids and solids on the surface of the earth. As the liquids and solids get warm from the sun they warm the air above them. The earth’s surface does not heat evenly due to sunlight hitting the earth at different angles. In addition to the angles affecting temperature so does time of day and seasons. It is usually coolest in the morning before sunrise and warmest in the afternoon. Also, there are more hours of sunlight in the summer than in the winter, giving the earth’s surface more time to heat up.

Different Surfaces and Temperature Different surfaces absorb different amounts of light energy. Are your feet cooler on grass or on the sidewalk? For instance, the air temperature at Jones Beach is cooler because of the breeze from the ocean. Oceans heat up more slowly causing air temperature to be cooler than land surfaces. How do you find out what the air temperature is? Air temperature is measured by a tool called a thermometer. C on the thermometer stands for Celsius. Celsius is a metric scale for measuring temperature. What is the name of the measurement of temperature we commonly go by? GRASS? SIDEWALK?

Lesson 2: How Does Temperature Affect Air Movement? Air is made of matter and has mass. Air presses down on the earth and us. The pressing of air is called air pressure. Changes in temperature cause changes in air pressure. As the air near the earth’s surface becomes warmer, the particles of air move farther apart. The air becomes lighter and rises causing less pressure on its’ surface and us creating a low pressure area. Cold air is heavier than warm air. Its’ particles are much closer together, making the air heavier, causing more pressure on the earth and us; thus, a high pressure area is formed. How do you measure air pressure? Using a tool called a barometer will tell you the air pressure around you.

Measuring Wind Direction and Speed How can you measure wind when it is invisible? If you watch things move you can tell the direction of the wind. For a more exact measurement of the wind scientists use a wind vane. A wind vane is a tool that shows wind direction. A wind vane has a tail that is moved by the wind. On the opposite side it has an arrow that points to the direction of the wind, whether it is north, south, east, or west. A wind sock also shows wind direction, as well as wind speed. If the wind is high the sock will stand straight out. If it is a low wind it will barely lift up. For an accurate measurement of wind speed, scientists use a tool called an anemometer. Three or four cups are attached to a pole. As the wind pushes the cups around the wind speed is measured by how many spins per minute. wind vane wind sock anemometer

Lesson 3: What Causes Clouds and Precipitation? As we stated before warm air rises. As it rises it cools, as it distances itself from the earth. As it cools it becomes water vapor, which are tiny water drops. The more and more they gather they form a cloud. Since water vapor is needed to form a cloud, you will see many clouds in places where the air is very moist. Would you see many clouds in a desert?

Types of Clouds There are three types of clouds: Stratus, Cumulus, and Cirrus. The are very different in shape and size. The Stratus clouds are the low clouds that form flat, wide layers. The Cumulus clouds are dome shaped with flat bottoms. The Cirrus clouds look like thin threads or feathers arranged in bands.

Kinds of Precipitation/ Measuring Precipitation and Humidity Precipitation is moisture that falls from clouds to the ground. Rain, hail, snow, and sleet are examples of moisture that falls to the ground. A rain gauge is a tool that measures rain fall. It is an open-topped container that collects rain. Humidity is a measure of the amount of water vapor in the air. Humidity can be measured by using a hygrometer. A hygrometer uses a hair attached to a pointer. As the hair absorbs water vapor from the air, it gets longer. rain gauge hygrometer

Water Cycle Condensation-is when water vapor condenses and forms clouds. Precipitation-moisture that falls from the clouds. Evaporation- is when water enters the air as water vapor. Runoff-As the water falls to the ground some of it soaks in. The water that doesn’t runs downhill into puddles, streams, rivers, or lakes.

Lesson 4: How Do Meteorologists Predict Weather? Many things cause the air to change. One of those things is what is called air mass. Air mass is a large body of air that has about the same temperature and humidity throughout. Air masses can be warm or cold and can have a little or a lot of water vapor. Air masses typically move from west to east (California to New York). Sometimes as they travel they encounter another air mass. Air masses do not blend, they stay separated. Where two air masses meet is called a front. A cold front happens when a cold air mass pushes into a warm air mass causing thunderstorms or heavy rain. A warm front is when a warm air mass slides slowly over the top of a cold air mass causing light rain or snow for several days.

Tracking and Predicting Weather A forecast is a prediction of what the weather will be like for the next few days. A weather forecast is made by a meteorologist-a person who studies the weather. Many meteorologist get their information from the National Weather Service. This government agency has weather stations all over the United States.