As more water vapor condenses and the cloud droplets grow large enough, the water can fall as precipitation (rain, snow, or hail). Precipitation varies in type and amount in different parts of the world. Oceans, rivers, and lakes store this water. Infiltration allows some of the water to move underground into the groundwater and water table. Other water evaporates from the bodies of water, starting the water cycle all over again.
The water cycle plays an integral role in the measurements students are taking. Humidity is the measure of the amount of water vapor in the air. The hygrometer that the students are using measures relative humidity : the ratio of the amount of water vapor in the air to the maximum amount that the air could hold at its current temperature, expressed as a percentage. Students are also observing cloud types in the GLOBE measurements.
Cloud types
The oxygen cycle is critically important to sustaining the life on earth – without it, none of us would be alive! During photosynthesis , plants absorb carbon dioxide and sunlight and release oxygen to the atmosphere. Humans and other animals use the oxygen in the air. After the oxygen is used by the body, it is breathed back out as carbon dioxide in a process called respiration. Plants also consume some oxygen and release carbon dioxide through respiration .
The oxygen cycle
The oxygen cycle is closely intertwined with the carbon cycle. The carbon cycle is how all of the carbon atoms that exist move around on the earth and in the atmosphere. In photosynthesis , plants absorb sunlight and carbon dioxide in order to grow. The carbon is stored in the plants as sugars, starches, and other compounds. Animals eat these plants or other animals and the carbon moves into them. These animals, and humans too, release the carbon dioxide into the atmosphere when they breathe out. When plants and animals die, they decay, and the carbon is returned to the air or ground, where some of it can be reused by plants or small microorganisms. Over millions of years, some of the carbon can transform into fossil fuels. When these fossil fuels are burned by cars or factories, carbon dioxide is released into the air.
Despite its small concentration, carbon dioxide plays an important role – it acts as a greenhouse gas, keeping the Earth warm; plants use it for photosynthesis; and it is released when we breathe out or material decays. We will discuss carbon dioxide in much greater detail in Lesson 6.
The carbon cycle
Vocabulary
• Clouds
• Water Cycle
• Carbon cycle
• Oxygen cycle
• Humidity
• Relative Humidity
• Precipitation
• Condensation
• Evaporation
• Infiltration
• Transpiration
• Cirrus
• Cumulonimbus
• Cumulus
• Stratus
• Surface Water
• Respiration
• Photosynthesis
Materials (for a class of 25)
• Hygrometer (1)
• Infrared Thermometer (1)
• Ozone Test Strip (1)
• Ozone Scanner (1)