Lesson 1 Atmosphere and Weather
How does the Sun warm Earth? Insolation is the solar energy that reaches a planet. Insolation does not warm all places equally because of Earth’s shape. Which part of Earth is the warmest? This is because sunlight hits the equator at a vertical angle. When light hits Earth at a wider angle, there is more area to be warmed. A beam of sunlight always has the same amount of heat energy. *use students as particles of light in a light beam to show example*
Layers of the Atmosphere Atmosphere – all the gases that surround Earth. 5 layers of the atmosphere: Exosphere Thermosphere mesosphere stratosphere troposphere Weather – the condition of the troposphere at a particular time and place. Most weather occurs in the troposphere.
*does air have weight demonstration (2 balloons, string, yardstick) Air takes up space (balloon, tire) and it has weight. Air pressure – the force put on a given area by the weight of the air above it
What changes air pressure? Volume is a measure of how much space an object takes up. The more space the air has, the less the air pressure. Temperature: When air is heated, gas particles speed up and spread out which decreases air pressure. Height Above Earth’s Surface: the higher the altitude, the less air pressure. The Amount of Water Vapor: the more water vapor in the air, the lighter it becomes. (lower air pressure)
Humidity is the amount of water vapor in the air. Hygrometers measure the relative humidity in the air. Barometers measure the air pressure.
Lesson 2 Wind What is wind? Air moves from areas of high pressure to areas of low pressure. This causes wind. Global winds are winds that blow steadily over long distances in a predictable direction. Air close to the equator is heated more than air closer to the poles. This causes the air blow. Warm air is less dense so the particles of air are spread farther apart. Warm air rises in the atmosphere until it cools off.
Local Winds During the day, the sun warms land faster than it warms the water. This causes a sea breeze, the air moves from the ocean onto the land. Warm air rises and the cool air from over the ocean rushes to replace it. At night, the land cools faster than the water. This causes a land breeze, the air blows from the land toward the ocean.
Measuring Wind Weather vane – an instrument that shows which way the wind is blowing. Windsock can also show wind direction. Anemometer –instrument used to measure wind speed.
Lesson 3 Predicting Weather Scientists plot the air pressure of different areas on a map ad connect the places with the same air pressure. This line is called an isobar. Isobars can help estimate wind speed. Isobars spaced close together show faster wind speed. Air flows from high pressure to low pressure. (balloon) Different types of weather develop around high and low pressure. *High pressure – cool, dry air brings clear weather *Low pressure – warm, stormy weather.
Weather Fronts Air mass – a large region of the atmosphere in which the air has similar properties throughout. Air masses can be warm or cold and dry or humid. Over the water, they tend to be humid. Over land, they tend to be dry. A front is where air masses meet. Cold Front – brief, heavy storms followed by clear skies. Warm Front – light rain followed by warm, humid weather. Stationary front is a boundary between two different air masses where neither one is strong enough to replace the other. Almost all weather fronts in North America move from west to east. This helps us predict the weather.
Weather Map A weather map shows the weather in a specific area at a specific time. Cold Fronts = blue line with blue triangles Warm Fronts = red line with half circles. Meteorologists are scientists who study Earth’ atmosphere and weather. Weather predictions may not always be right because one slight change can change the weather.