1. Weather Brain Pop Weather

2. What is Weather? Weather is the condition of Earth’s atmosphere from day to day. Earth’s atmosphere is the envelope of gases that surrounds the planet. Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids. What is Earth’s Atmosphere?

3. Importance of the Atmosphere 1. Earth’s atmosphere makes conditions on Earth suitable for living things. 2. The atmosphere contains gases that living things need. 3. The atmosphere protects living things from harmful radiation from the sun.

4. Importance of the Atmosphere 4. The atmosphere keeps the Earth’s surface warm for water to exist as a liquid. 5. The atmosphere prevents meteoroids from hitting the Earth.

5. Layers of the Atmosphere The Earth’s atmosphere can be divided into four main layers: the troposphere, the stratosphere, the mesosphere, and the thermosphere.

6. Layers of the Atmosphere 1. The troposphere is the layer of the atmosphere in which Earth’s weather occurs. 2. The stratosphere is the second layer of the atmosphere and contains the ozone layer. 3. The third layer, the mesosphere protects the Earth’s surface from being hit by most meteoroids. 4. The last layer, the thermosphere blends gradually into outer space.

7. Energy in Earth’s Atmosphere Most of the energy from the sun travels to Earth in the form of visible light and non-visible light called infrared radiation and some ultraviolet radiation. Some sunlight is absorbed or some reflected (back into space) by the atmosphere and the rest reaches the Earth’s surface. When Earth’s surface is heated, it radiates most of the energy back into the atmosphere. Radiation, conduction, and convection work together to heat the troposphere to influence our weather.

8. Water in the Atmosphere The movement of water between the atmosphere and Earth’s surface is called the water cycle (sound familiar?). Humidity is the measure of the amount of water vapor in the atmosphere. ◦ Warm air can hold more water vapor than cool air. A psychrometer is used to measure humidity. Clouds form when water vapor in the air condenses to form liquid water or ice crystals. Types of precipitation are rain, sleet, freezing rain, snow, and hail. A rain gauge is used to measure the amount of rain. Brain Pop on Atmosphere

9. Air Pressure Air has mass, it also has other properties such as density and pressure. Density is the amount of mass in a given volume of air. Pressure is the force pushing on an area or surface.

10. How can air pressure be measured? A barometer is an instrument that is used to measure air pressure. Most weather reports use inches of mercury as their units to measure air pressure.

11. How can air pressure be measured? Air pressure decreases as altitude (elevation) increases. As air pressure decreases, so does density. KEY POINT: Changes in air pressure can help determine if a storm is approaching.

12. Winds Winds are caused by differences in air pressure. Most differences in air pressure are caused by the unequal heating of our atmosphere. Convection currents form when warm air rises (heated by the sun) and is quickly replaced by cool air causing wind. Wind speed can be measured by an anemometer.

13. Types of Winds Types of Winds Local winds are caused by the unequal heating of Earth’s surface within a small area such as a sea breeze or a land breeze. Global Winds are created by the unequal heating of Earth’s surface over a large area such as the prevailing westerlies and jet streams. Brain Pop Wind

14. Air Masses and Fronts A huge body of air that has similar temperature, humidity, and air pressure at any given height is called an air mass. Four major types of air masses influence the weather in North America are the maritime tropical, continental tropical, maritime polar, and continental polar. In the continental United States, air masses are commonly moved by the prevailing westerlies and jet streams.

15. Air Masses in North America

16. Types of Fronts Air masses do not mix easily. The boundary where the air masses meet becomes a “front”. Colliding air masses can form four types of fronts: cold fronts, warm fronts, stationary fronts, and occluded fronts.

17. Types of Fronts A cold front is when a fast moving cold air mass overtakes a warm air mass bringing cold temperatures and sometimes thunderstorms. A warm front happens when a warm air mass overtakes a slow moving cold air mass bringing warmer temperatures and sometimes rain.

18. Types of Fronts A stationary front happens when cold and warm air masses meet and neither can move the other and can bring precipitation. An occluded front occurs when a warm air mass is caught between two cooler air masses, temperatures near the ground are cool because the warm air mass is cut off.

19. Storms A storm is a violent disturbance in the atmosphere. Storms involve sudden changes in air pressure and cause rapid air movements. The different type of storms that can exist are thunderstorms, tornadoes, and hurricanes. Natural Disasters

20. Thunderstorm A thunderstorm is a small storm with heavy precipitation and frequent thunder and lightning. BrainPop Thunderstorm BrainPop Thunderstorm

21. Tornadoes Tornadoes form when cold air moves under warm humid air forcing it to rise rapidly. BrainPop Tornado

22. Hurricanes Hurricanes begin over warm ocean water as a low pressure area, or tropical disturbance. If the tropical disturbance grows in size and strength, it becomes a tropical storm, which may become a hurricane. Brain Pop on Hurricanes

23. Predicting the Weather Meteorologists use maps, charts, and computers to analyze weather data and to prepare weather forecasts. Standard symbols on weather maps show: 1.fronts 2.areas of high and low pressure 3.types of precipitation 4.temperatures For example, a capital H stands for an area of high pressure which means good clear weather. A capital L stands for an area of low pressure which means bad stormy weather. Current Weather Map

24. Weather Map Example