Adapted with permission by National Oceanic and Atmospheric Administration.
No matter where we are on Earth, we can observe changes in vegetation. Some changes are drastic, such as going from dormant to full growth during a temperate winter.
Vegetative growth is dependent on both surface temperature (which influences soil temperature) and precipitation (which influences soil moisture). Together these environmental variables help determine the beginning, duration, and end of the growing season; the latter marked by leaf senescence, when leaves of deciduous trees die and turn colors.
- Notebook and pen
- Computer with Internet access
- Digital GLOBE Earth System Poster (Biosphere animated images) at http://mynasadata.larc.nasa.gov/globe
- GLOBE Earth System Poster (Insolation, Surface Temperature, Precipitation, and Cloud Fraction images) at www.globe.gov/documents/10157/334459/EarthSystemPoster07_print.pdf
- Additional images at www.globe.gov/teaching-and-learning/materials/earth-system-science-posters
1. View animated biosphere images in the Digital GLOBE Earth System Poster.
2. Discuss patterns you observe, such as the blue and green colors slowly moving north on map images, then retreating. Consider:
- You are observing Earth’s annual “greening” through satellite images in the way many scientists do — through remote sensing, that is, observing something without actually coming in contact with it. Satellites sense, or observe, remotely, from a distance. Images created by instruments on satellites are interpreted by scientists wanting to learn more about global processes.
- These biosphere images are of Normalized Difference Vegetative Index (NDVI). NDVI show the amount of infrared light, energy, reflected by plants. Green plants absorb solar energy through photosynthesis.
- Healthy plants reflect highly in the near-infrared part of the electromagnetic spectrum. NDVI provides an estimate of plant health and allows scientists the ability to monitor changes in vegetation over time.
- These NDVI images show plants growing during photosynthesis and reflecting in the near-infrared through the growing season, then going dormant during winter in the Northern latitudes. NDVI in the tropics appears to change very little.
3. View the images again, this time observing the dates (top left of the images). In your notebook, record when the Northern Hemisphere becomes the greenest and the least green. Write a hypothesis for what factors might be influencing these changes.
4. Observe the Insolation, Surface Temperature, and Precipitation images from the GLOBE Earth System Poster. Compare your hypothesis for increased greenness with these images.
5. Write in your notebook: What is the connection between greenness (NDVI) and surface temperature? How does insolation influence surface temperature? How might precipitation influence the growing season?
6. The Precipitation images display an area between 45o north and 45o south; the use of Cloud Fraction images can be used in the northern and southern latitudes as a supplement. Cloud Fraction images show the locations of clouds as a percentage (strong white indicates the presence of clouds). These images can be used with the assumption that strong white areas may indicate the presence of precipitation.
7. Write in your notebook: How might significant changes in precipitation (when and where precipitation falls, as well as how much falls) affect plant health? How could this be assessed through NDVI images?
Get involved in monitoring your local environment through GLOBE at www.globe.gov.