To download the animations and accompanying color palettes, right click (or click and hold for Mac users) on the link and select "save link as" or "save target as."
From October 1979 to October 2000, is there a pattern of stratospheric ozone levels according to region?
There is a pattern of stratospheric ozone levels according to region. Higher ozone levels are typically found in Northern and Southern Hemispheres, and lower ozone levels are found in the equatorial region. Significantly lower ozone levels are found at the South Pole.
What changes in ozone levels do you see over time? Pick at least two regions, and then compare and contrast.
Generally, the ozone levels decreased from 1979 to 2000. A significant decrease can be seen at the South Pole. Other significant decreases in the ozone levels can be found in Africa, Asia, and North America.
What might be causing these changes in the ozone level?
The changes are due to the following: Pollution (CFC emission, factories); Volcanic eruptions.
Compare and contrast surface temperature patterns of the Earth in January and June 1990.
Surface temperatures along the equator do not change significantly, whereas temperatures are significantly different at higher latitudes, particularly over Asia, Europe, and North America. Surface temperatures in January are low in the Northern Hemisphere and high in the Southern Hemisphere, while in June surface temperatures are high in the Northern Hemisphere and low in the Southern Hemisphere.
Why do surface temperatures at the equator remain relatively constant, while surface temperatures of the two hemispheres change?
The Earth rotates on its axis as it revolves around the sun. When the tilt of the axis is toward the sun, it is summer in the Northern Hemisphere, because the Northern Hemisphere receives more sunlight, and winter in the Southern Hemisphere. When the tilt of the axis is away from the sun, it is winter in the Northern Hemisphere and summer in the Southern Hemisphere. Because the equator is the boundary between the Northern and the Southern Hemisphere, there is little change in the amount of exposure to the sun. Therefore, the surface temperatures remain relatively constant along the equator.
Focus on Africa. What patterns of fire and precipitation do you see?
Basically, in Africa when there is more precipitation there is less fire, and vice versa.
Focus on Africa. What is the relationship between the fire and precipitation over time?
There is a relationship between the rainy seasons and human activity. In the summer and early fall, there is more precipitation and less fires in northern Africa. In southern Africa, there is less precipitation and more fires due to slash-and-burn, agriculture, and deforestation. In the late fall and winter, there is more precipitation and less fires in southern Africa. In northern Africa, there is less precipitation and more fires again, due to slash-and-burn, agriculture, and deforestation.
Focus on the higher northern latitudes. Do they follow the same pattern of fire and precipitation as Africa? Explain.
No they do not. There are fires at high northern latitudes in the summer months, even though there is precipitation. These are primarily the result of lightning strikes hitting the surface and, to a lesser degree, fires caused by humans. There are few fires in the winter months because there is a lot of snow and little lightning.
What are some things that cause the fires?
Deforestation/slash-and-burn farming
Lightning strikes hitting the surface
Accidental fires caused by humans
"Prescribed burns," or fires deliberately set by forest resource managers to help maintain the health of the ecosystem while minimizing the risk of larger, uncontrolled wildfires later
What patterns of vegetation and precipitation do you see?
As the precipitation increases the plant productivity increases, and vice versa.
What is the relationship between vegetation and precipitation and time?
From the months of April through September, the Northern Hemisphere is mostly green and generally has high precipitation. In the months of October through April, the Southern Hemisphere is green and has high precipitation. (Remember that summer in the Southern Hemisphere occurs during winter in the Northern Hemisphere.) The equator typically is green and has high precipitation all year.
Notice on the globes where there is no vegetation, where the amount of green vegetation remains constant, and where the amount of green vegetation changes seasonally. Can you identify the biomes associated with these regions?
Where there is no plant productivity, there are either deserts or polar ice caps. Where the amount of green vegetation remains constant, there are rain forests. Where the amount of green vegetation changes seasonally, there is one of the following:
In the animation, how can you recognize El Niño and La Niña years?
In the southern Pacific, warmer than normal sea surface temperatures indicate El Niño (red), and colder than normal sea surface temperatures indicate La Niña (blue).
Focus on the Amazon. What is the pattern of vegetation anomalies and sea surface temperature?
South America generally experiences decreased plant productivity (indicated by brown hues) during El Niño and increased plant productivity (green hues) during La Niña.
In the tropical regions of both hemispheres, winds generally blow from the east to the west. How do the winds and sea surface temperatures affect plant growth in the Amazon?
When the southern Atlantic Ocean is colder than normal, less water will evaporate. Therefore, there will be less water vapor transported westward and, consequently, less precipitation in the tropical regions of South America. When the Atlantic Ocean is warmer than normal, more water will evaporate. Therefore, there will be more precipitation to the west. Less precipitation means less green plant productivity, and vice versa.
At high latitudes in both hemispheres, winds generally blow from the west to the east. How do the winds and sea surface temperatures affect plant growth in North America? In Australia?
During El Niño, there is also typically a large pocket of warmer-than-average water along the west coast of North America. Therefore, there is more precipitation in the southwestern United States causing the relatively rapid appearance of grasslands where there is desert! Similarly, greening and drought trends across Australia appear to be linked to sea surface temperature patterns in the southern Indian Ocean.
How does precipitation change over the course of one year in East Asia?
The amount of precipitation increases during the summer months in East Asia. In the winter months, there is little to no precipitation.
How would people living in this region be affected by the weather pattern?
During the winter months, inhabitants of this region face severe drought conditions. During the summer months, monsoon rains irrigate the land and begin the growing season.
Discuss some of the patterns you see in the animation.
Where there is higher cloud cover, there is more sunlight reflected. However, it is not always true that when there is high reflected sunlight, there is high cloud cover. Snow and ice are highly reflective, as are atmospheric aerosols.
What are some other factors besides clouds that might cause the high shortwave radiation? (Hint: Carefully observe Africa and the poles.)
Africa: Near the Sahara Desert, there is virtually no cloud cover and yet there is relatively high values of reflected sunlight. The sand is highly reflective.
Either pole: There are low cloud fractions and high shortwave radiation at the poles. The ice causes high reflection, and therefore, the high shortwave radiation.
Notice that in general there is higher reflected shortwave radiation in the summer. Why is this true?
Reflected shortwave radiation is higher in the summer because the tilt of the Earth is toward the sun, causing an increase in radiation exposure. Heats surface, greater convection, more rain-clouds.
Discuss some of the patterns you see in the animation.
The high surface temperature contributes to an increase in the plant productivity.
In general, why does higher surface temperature increase the amount of vegetation?
Warmer temperatures help plants photosynthesize more efficiently and, therefore, increase the amount of production of green foliage.
Carefully observe the changes in temperature and in vegetation from March 1987 to July 1987 in the Boreal region. Does green vegetation increase at the same time surface temperature increases? Or, does surface temperature increase and then green vegetation increases?
There is sometimes an obvious lag between increasing temperature and plant productivity in this latitude. In this region it takes the ground longer to thaw, which causes a lag time between the onset of spring and plant growth.
Why does higher surface temperature have no effect on vegetation in some of the regions?
Due to lack of precipitation, there is little or no vegetation present in the desert and areas suffering from drought, despite warmer temperatures.
Discuss some of the patterns you see in the animation.
Where there are clouds there is low outgoing heat radiation. At low latitudes, there is high outgoing radiation except along the Intertropical Convergence Zone (ITCZ), where you're seeing cold cloud tops. Outgoing heat radiation changes with the seasons.
Focus on the Amazon. We know that the Amazon has high surface temperatures. Explain why the outgoing radiation is low.
Where there is less heat emitted, there are more clouds that trap the heat at the surface.
As you know, the Amazon is a rainforest. Apply the data set and the animation you have just seen to define the characteristics of a rainforest.
A tropical rainforest is a hot, moist biome where it rains all year long. The data set clearly shows cloud cover over the Amazon all year. This would indicate possible precipitation all year long. The data set also indicates that little heat is emitted from the Amazon region, implying that the heat is trapped at the surface.
From August 1999 to February 2000, do the locations of fires change over time?
The locations of fires do change over time. For example, in South America, the fires move from southeast to northwest. In Africa, the fires move up toward the north.
What would cause the locations of fires to move?
The locations of fires move because the fires move with the growing seasons.
As you carefully observe the animation, you see that the amount of green vegetation changes with the seasons. Notice that the changes in green vegetation are dramatic in the Northern Hemisphere. Use the landcover data sets to determine why there is a difference between the two hemispheres.
The Northern and Southern Hemisphere are in opposite phase through the seasons.
Are there patterns according to region and season?
The high northern latitude boreal evergreen forests maintain some "greenness" (or NDVI) during winter months. The tropical rainforests of the Amazon and central Africa also appear green all year long. In other regions where there are deciduous forests, plant productivity is highly seasonal and typically reaches maximum greenness during the spring and summer months. Focus on Egypt and note the greenness around the Nile River Delta and southward along the Nile down through the Sahara Desert. This plant productivity is caused by agricultural irrigation.
Is there a correlation between the two data sets?
There is a strong correlation between the two data sets. Greenness values (NDVI) remain high in regions where there are evergreen forests, while NDVI values wax and wane through the seasons in regions where there are deciduous forests.
