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Atmosphere, Climate



The Camanchaca - the role of fog in the Earth system

When most of us think of fog, we think of it as a nuisance, something that hampers air travel and even causes large pileups on an autobahn or freeway. If you are involved in communications, you know fog attenuates the laser beam carrying data.

Most don't realize that fog has an important role in the Earth system. Some of the greatest forests on Earth like the Redwoods of coastal California and the giant ashes of Australia owe their existence to fog. Perhaps nowhere in the world can the importance of fog in maintaining coastal forests be seen better than in Parque Nacional Fray Jorge, Chile. This park exists in a coastal desert where rainfall is about 4 inches (about 100 mm) per year, and when one enters the park, you see the dry scrub and cactus that you would expect in such a desert climate. Traveling into the coastal hills, an amazing transformation occurs: dense forest appears - forests similar to those you would see much farther to the south where rainfall exceeds 40 inches (about 1,000 mm) per year.

To the right is a picture of the desert region of the park outside of the fog area.
Below it is a picture of the dense foliage that exists in the park's fog forest.

Many years ago, the story was told of an Aymara Indian who planted a tree in the foggy desert and how it thrived. A more modern story began in 1967, when a cypress tree was planted in the foggy desert of Norte Grande province in Northern Chile. As far as rainfall is concerned, this area, near Antofagasta, Chile, may be the driest area in the world - receiving less than 5 mm (0.2 inch) of rain per year. Initially, a fog trap made of nylon mesh provided moisture for the tree, but as the tree grew, it was able to capture the moisture on its own, enough to contribute to undergrowth and even to groundwater (Gischler, 1991). This fog, which flows inland over the Pacific Ocean is called Camanchaca by the Aymara Indians who live in Northern Chile.

Reference: Gischler, C.,1991. The missing link in a production chain: Vertical obstacles to catch Camanchaca, UNESCO: Montevideo.



After several years of drought, the San Francisco Bay area has experienced a severe water shortage. The hilly ocean exposed areas north and south of the city experience persistent fog, especially during the summer months. The Bay Area Water Supply and Conservation Agency (BAWSCA) is aware of the success of fog harvesting in the arid coastal regions of Chile and other locations. Your team of Earth system scientists has been asked to study the feasibility of fog harvesting as a water source for San Francisco Bay area communities. Your team should do an Earth system analysis to examine this issue and any possible environmental impacts associated with such a project.


Date: 8/26/2008

Scenario Images:

Desert region
Desert region of Fray Jorge (outside of the fog forest)

The Fog Forest
Dense foliage in Parque Nacional Jorge Fray



FogQuest (Cycle A)
This site provides links to fog harvesting projects now being conducted worldwide by FogQuest.


The Camanchaca - a water resource (Cycle A)
This is an older scholarly article about the Camanchaca and its potential. Click on PDF to access the entire article.


BBC Weather Fog (Cycle B)
Gives concise defintions of different types of fog.


Fog Dissipation (Cycle B)
Fog dissipation is often a goal for airport and highway safety. This article describes some techniques used in fog dissipation.


Fog trends in Los Angeles (Cycle B)
This article discusses how dense fog has decreased in the Los Angeles area over the past 50 years and possible explanations.


Fog types (Cycle B)
This link describes the different types of fog and how they form.


More on fog types (Cycle B)
Describes specific types of fog including valley fog, freezing fog and ice fog.


Fog in New Delhi and cooler maximun temperatures (Cycle C)
This article describes how recent increases in fog in New Delhi have affected maximum temperatures.


The Donora Pennsylvania smog (Cycle C)
Describes the Donora Pennsylvania smog of 1948.


The Great Smog of 1952 (Cycle C)
The great London smog of 1952 is discussed. Its causes, and the excess deaths and low visibilities that resulted are described.


Sample Investigations:


Advection fog on the California coast (Cycle A)
This is a loop of a typical advection fog occurrence on the California coast.
Difficulty: beginner


GOES Image search (Cycle A)
This is a link to the GOES archive. See if you can determine areas of fog by examining archived visible and infrared imagery. (Hint: look for summertime images along the West coast of the United States.)
Difficulty: intermediate


Nightime Fog and Low Cloud images from GOES and NOAA Polar satellites (Cycle B)
This website shows how infrared satellite imagery can aid in the detection of fog and low clouds at night. Real-time images can be viewed and interpreted.
Difficulty: advanced


West Coast Fog (Cycle B)
This is an advanced investigation of west coast marine fog - the type of fog that affects the west coasts of continents. To access this module, you must first register (free) at
Difficulty: advanced


Identifying fog on satellite imagery (Cycle C)
This module from Johns Hopkins University describes how to identify fog by using infrared and visible meteorological satellite imagery.
Difficulty: intermediate


Make Fog in a Jar (Cycle C)
This activity from the University Corporation for Atmospheric Research shows how the cooling of water vapor and the addition of condensation nuclei (from the matches) results in the formation of clouds or fog.
Difficulty: beginner




  • Science
    National Science Education Standards - Science Content Standards The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
      • Science as Inquiry (Std A)
        • Abilities necessary to do scientific inquiry
        • Understanding about scientific inquiry
      • Science as Inquiry (Std A)
        • Abilities necessary to do scientific inquiry
        • Understanding about scientific inquiry
  • Geography
    Geography for Life: National Geography Standards, 1994
      The physical environment is modified by human activities, largely as a consequence of the ways in which human societies value and use Earth’s natural resources, and human activities are also influenced by Earth’s physical features and processes. The geographically informed person knows and understands:
      • How human actions modify the physical environment
      • How physical systems affect human systems
      • The changes that occur in the meaning, use, distribution, and importance of resources
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