Atmospheric Structure
Not only does the atmosphere have a relatively stable composition, but it also has a structure to it. Below are two figures from Lutgens and Tarbuck (The Atmosphere, 8th edition) showing vertical profiles of the atmosphere. Note that the first major break, or boundary in the atmosphere as we ascend is the tropopause.
Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees. The precipitation is so eratic that drought and fire prevent large forests from growing. Grasses can survive fires because they grow from the bottom instead of the top. Their stems can grow again after being burned off. The soil of most grasslands is also too thin and dry for trees to survive.
When the settlers of the United States moved westward, they found that the grasslands, or prairies as they called them, were more than just dry, flat areas. The prairies contained more than 80 species of animals and 300 species of birds, and hundreds of species of plants.
There are two different types of grasslands; tall-grass, which are humid and very wet, and short-grass, which are dry, with hotter summers and colder winters than the tall-grass prairie. The settlers found both on their journey west. When they crossed the Mississippi River they came into some very tall grass, some as high as 11 feet. Here it rained quite often and it was very humid. As they traveled further west and approached the Rocky Mountains, the grass became shorter. There was less rain in the summer and the winters got colder. These were the short-grass prairies.
Grassland biomes can be found in the middle latitudes, in the interiors of continents. They can have either moist continental climates or dry subtropical climates. In Argentina, South America, the grasslands are known as pampas. The climate there is humid and moist. Grasslands in the southern hemisphere tend to get more precipitation than those in the northern hemisphere, and the grass tends to be the tall-grass variety.
There is a large area of grassland that stretch from the Ukraine of Russia all the way to Siberia. This is a very cold and dry climate because there is no nearby ocean to get moisture from. Winds from the arctic aren’t blocked by any mountains either. These are known as the Russian and Asian steppes.
In the winter, grassland temperatures can be as low as -40° F, and in the summer it can be as high 70° F. There are two real seasons: a growing season and a dormant season. The growing season is when there is no frost and plants can grow (which lasts from 100 to 175 days). During the dormant (not growing) season nothing can grow because its too cold.
In tropical and subtropical grasslands the length of the growing season is determined by how long the rainy season lasts. But in the temperate grasslands the length of the growing season is determined by temperature. Plants usually start growing when the daily temperature reached about 50° F.
In temperate grasslands the average rainfall per year ranges from 10-30 inches. In tropical and sub-tropical grasslands the average rainfall per year ranges from 25-60 inches per year The amount of rainfall is very important in determining which areas are grasslands because it’s hard for trees to compete with grasses in places where the uppers layers of soil are moist during part of the year but where deeper layer of soil are always dry.
The most common types of plant life on the North American prairie are Buffalo Grass, Sunflower, Crazy Weed, Asters, Blazing Stars, Coneflowers, Goldenrods, Clover, and Wild Indigos.
Some common animals in the grasslands are Coyotes, Eagles, Bobcats, the Gray Wolf, Wild Turkey, Fly Catcher, Canadian Geese, Crickets, Dung Beetle, Bison, and Prairie Chicke
Further Readings:
Geothermal energy – literally heat from the earth – is a clean and versatile natural resource for the world’s steadily increasing energy needs.
GEOTHERMAL RESOURCES
When the rising hot water and steam is trapped in permeable and porous rocks under a layer of impermeable rock, it can form a geothermal reservoir.
© Geothermal Education Office, Tiburon, CA
Earth’s natural geologic processes, such as those associated with geysers and hot springs, allow magma to rise relatively close to the earth’s surface. In places like the “Pacific Ring of Fire,” the magma heats vast regions of underground rock located high above the magma chambers. Often porous and fractured, the hot rock can become saturated with rainwater that has seeped underground, creating geothermal reservoirs of hot water and steam. Geothermal reservoirs vary in temperature – sometimes reaching as high as 700°F (371°C).
Geothermal heat and geothermal reservoirs are generally referred to as geothermal resources and are located in many parts of the world. In the United States, they occur primarily in the western states including California.
ELECTRIC POWER GENERATION
Many areas have accessible geothermal resources, especially countries along the circum-Pacific “Ring of Fire,” spreading centers, continental rift zones and other hot spots.
© Geothermal Education Office, Tiburon, CA
High temperature geothermal resources, usually above 300°F (149°C), are generally used for electric power generation. To access the high-temperature geothermal resources, production wells are drilled. From the wells, the steam or hot water is brought to the surface and piped to a geothermal power plant where its energy is used by a steam turbine to generate electricity. After the geothermal water does its work in the power plant, it is piped back into the geothermal reservoir – and the cycle continues. Geothermal power plants operate 24 hours a day, since the “fuel” source is always available; these plants are therefore valued for their ability to provide us with baseload electricity.
Natural steam from the production wells power the turbine generator. The steam is condensed by evaporation in the cooling tower and pumped down an injection well to sustain production.
© Geothermal Education Office, Tiburon, CA
The methods and equipment used to drill geothermal wells in high-temperature water-dominated reservoirs are very similar to those used to drill oil and gas wells. Modern oil wells using rotary drills can reach depths of 38,000 ft. (11,600 meters). The deepest oil well penetrates a mere six miles (ten kilometers) into the crust while the center of the Earth is about 4,000 miles (6,400 kilometers) deeper (http://magma.nationalgeographic.com/ngm/0404/resources_who.html).
Geothermal wells usually range from 500 feet (152 meters) to 12,000 feet (3,700 meters) deep.
Because geothermal energy uses natural steam to operate the turbine-generator in a geothermal power plant, it is a clean energy resource. With geothermal energy no fossil fuels (such as coal or gas) are burned to create steam, so there are no smoky emissions. The cooling towers emit mostly water vapor (steam) as a by-product of generating electrical power.
Some geothermal power plants, Binary Power Plants, have no emissions at all.
Geothermal power plants emit water vapor (not smoke).
The first geothermal power plants in the U.S. were built in 1962 at The Geysers dry steam field, in northern California. It is still the largest producing geothermal field in the world.
© Geothermal Education Office, Tiburon, CA
Around the world there are about 11,000 MW of geothermal electricity generated in 22 countries. Current U.S. geothermal electric power generation totals approximately 2200 MW (or about the same as four large nuclear power plants). California’s geothermal power plants have a dependable installed capacity of over 1,800 megawatts – producing about 5 percent of California’s total electricity (more than all other renewables combined, excluding large hydro).
Geothermal power plants use three methods to generate electricity – dry stream, flash steam, and binary:
Dry Steam Power Plants
The first geothermal power plants in the U.S. were built in 1962 at The Geysers dry steam field, in northern California. It is still the largest producing geothermal field in the world. Located about 100 miles north of San Francisco, The Geysers is one of only two locations in the world (the other is Larderello, Italy) where a high-temperature, dry steam resource is used to turn turbines and generate electricity. In dry steam power plants, the steam (and no water) shoots up the wells and is passed through a rock catcher (not shown) and then directly into the turbine. Dry steam fields are rare.
In dry steam power plants, the steam (and no water) shoots up the wells and is passed through a rock catcher (not shown) and then directly into the turbine. Dry steam fields are rare.
© Geothermal Education Office, Tiburon, CA
Flash Steam Power Plants
Most geothermal plants today use a flash system, one which uses a resource of superheated water rather than steam only. In flash plants, as hot water is released from the pressure of the deep reservoir in a flash tank, some if it flashes to steam. Geothermal power plants in California that use flash steam are located in the Imperial Valley/Salton Sea area east of San Diego, and in the Coso Hot Springs area near Bakersfield.
Flash steam power plants use hot water reservoirs. In flash plants, as hot water is released from the pressure of the deep reservoir in a flash tank, some if it flashes to steam.
© Geothermal Education Office, Tiburon, CA
Binary Power Plants
The third geothermal power technology, found in binary power plants, takes advantage of resources that would not be hot enough to generate electricity in either a dry steam or flash plant. Binary technology uses a heat exchanger to transfer heat from the geothermal water to vaporize a “working fluid.” The vapor, like steam, powers the turbine. Because binary technology involves a “closed loop” system it is emission-free. Geothermal power plants in California that use the binary system are found in the southern Sierra area of Mammoth and near Honey Lake in the northeastern part of the state. There is also some use of binary technology in the Imperial Valley.
In a binary cycle power plant (binary means two), the heat from geothermal water is used to vaporize a “working fluid” in separate adjacent pipes. The vapor, like steam, powers the turbine generator.
© Geothermal Education Office, Tiburon, CA
It is estimated that California has a potential of more than 4,800 megawatts of additional power from geothermal energy, using these current technologies.
For more information about geothermal power plants in California, see Geothermal Electric Power Generation in California.
DIRECT (NON-ELECTRIC) USES
Bathing in hot pools like these at Hot Creek, Mammoth Lakes, California, has been practiced throughout history. Be careful – people and animals have been burned badly in unfamiliar pools.
© Geothermal Education Office, Tiburon, CA
Direct use projects use geothermal resources for their heat, applying the heat “directly” without generation of electricity. Such projects include space heating (individual buildings or whole districts), warming greenhouses, aquaculture (growing of fish), spas and swimming pools, and industrial processes.
Geothermal water flows through ceiling pipes to heat the plants in this greenhouse.
In several western US states, many long greenhouses are built and heated with geothermal water. This one is in New Mexico.
© Geothermal Education Office, Tiburon, CA
Pipes of geothermal water can be installed under sidewalks and roads to keep them from icing over in winter, like this sidewalk in Klamath Falls, Oregon.
© Geothermal Education Office, Tiburon, CA
Direct use projects generally use geothermal water at temperatures between 100°F (38°C) to 300°F (149°C). Current U.S. installed capacity of direct use systems totals enough to heat 40,000 average-sized houses. U.S. geothermal greenhouses today cover more than 110 acres, and domestic aquaculture annually yields about 40,000,000 pounds (18,000,000 kilograms) of fish.
Geothermal heating systems are remarkably durable. One system in Boise, Idaho, has been operating continuously since 1892, and its two original production wells are still in service.
Hot water from one or more geothermal wells is piped through a heat exchanger plant to heat city water in separate pipes. Hot city water is piped to heat exchangers in buildings to warm the air.
© Geothermal Education Office, Tiburon, CA
Depending upon water quality, the local environment, and project-permitting requirements, the used geothermal waters are either discharged at the surface or injected back into the geothermal reservoir to be reheated and reused.
Direct use of geothermal energy tends to make energy costs competitive and predictable. It is reliable, clean, sustainable, and helps to conserve fossil-fuel resources.
For more information about geothermal direct use projects in California, see Direct Use Projects in California.
GEOTHERMAL HEAT PUMPS
Another type of geothermal application – geothermal, or ground-source, heat pumps – uses underground heat that is relatively close to the surface. These systems — sometimes referred to as GeoExchange systems — do not depend on deep underground geothermal reservoirs, so they can be used almost everywhere in the world.
A geothermal heat pump is a unique mechanical device that conveniently heats and air conditions buildings and heats domestic hot water. It is one of the most efficient technologies available for home and workplace heating and cooling. These systems do the work that ordinarily requires two appliances, a furnace and an air conditioner.
The temperature of the ground, a few feet beneath the earth’s surface, remains relatively constant throughout the year, even though the outdoor temperature may fluctuate greatly with the change of seasons. Geothermal heat pumps rely on this relatively constant temperature of the earth (or groundwater) as a heat source in winter and a heat “sink” in summer. The resource temperatures, 37°F (2.7°C) to 74°F (23°C), are the natural temperatures just a few feet underground in many places in the world. In California, for example, at a depth of approximately six feet, underground temperatures remain stable between 52° F (11°C) and 74°F (23°C).
A geothermal heat pump transfers warmth from the underground to the house in winter and warmth from the house to the underground in summer. In the winter, the pump collects the earth’s natural heat through this configuration of closed pipes, called loops, installed below the surface of the ground — at 350 feet (107 meters) or less — or submersed in a pond or lake. Water circulating in the loop carries this heat to the building.
Different styles of pipes are installed beside a building. A liquid is piped through the pipes to pick up the heat FROM the ground or (in the summer) to bring heat from the building TO the ground.
© Geothermal Education Office, Tiburon, CA
In summer the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the earth. Geothermal heat pumps provide cooling much the same way as a refrigerator, which keeps its contents cool by drawing heat from the interior of the refrigerator and expelling it outside.
Accurate data is not available on the current number of these systems; however, the rate of installation is thought to be between 10,000 and 40,000 per year. Geothermal heat pumps are becoming more popular as our need to conserve energy becomes more urgent. There is potential for much greater use of geothermal heat pumps in California.
Geothermal heat pumps provide clean energy, conserve fossil-fuel resources, and are both energy- and cost-efficient. The U.S. Environmental Protection Agency has declared these systems to be the most environmentally friendly and efficient heating and cooling systems available.
linkks:http://cgec.ucdavis.edu/pages/energy.html
en.wikipedia.org/wiki/Geothermal_power
In three years when India sends the Chandryaan-1 to the moon, the country will join the elite lunar club. ISRO has already made it clear that the Indian lunar mission will not be an exercise in reinventing the wheel. Chandrayaan-1 will strive to unravel the hitherto unknown features of the moon for the first time. Moreover, Dr. Nair points out that a lunar mission can provide impetus to science in India, a challenge to technology and possibly a new dimension to international cooperation. Also on the agenda are the preparation of the three dimensional atlas of the regions on the moon and the chemical mapping of the entire lunar surface.
Sometime in 2007, when the first Indian scientific mission to the moon Chandrayaan-1 zooms into space at the head of the four-stage Indian built space vehicle—the Polar Satellite Launch Vehicle (PSLV), India will join the elite club of space faring nations that have the wherewithal to undertake such complex and challenging space missions.
The Chandrayaan-1 mission that involves placing of a 525-kg.spacecraft around the lunar orbit, will help expand the scientific knowledge about the moon besides upgrading India’s technological competence and providing challenging opportunities for planetary research to the younger generation.
For India, which began its space journey in a modest way in 1963 with the launch of a 9-kilo rocket from a research facility at the fishing hamlet of Thumba in Kerala, the Chandrayaan-1 marks a quantum leap. Indeed, India’s unmanned scientific mission to moon, which was approved last year, has moved further up India’s priority list in the wake of China’s successful manned mission of October 2003.
G.Madhavan Nair, Chairman, Indian Space Research Organisation(ISRO) says that the 294-tonne PSLV will launch Chandrayaan-1 from the Satish Dhawan Space Centre in Sriharikota.
The PSLV, originally developed with a view to serve as a workhorse for launching the Indian made IRS series of earth observation spacecraft, was subsequently promoted as a cost effective booster for launching light-weight piggyback payloads on a commercial basis. It has already accomplished two successful missions.
Satellite Payloads
During its May 1999 flight, PSLV launched India’s 1050-kg.IRS-P4 earth to ocean watch satellite along with the South Korean 107-kg.Kitsat probe and Germany’s 45 kg
Tubsat capsule. This was the first time that an Indian space vehicle launched three satellite payloads in orbit.
During its second commercial mission in October 2001, PSLV placed three satellites in their specified orbits–India’s Technology Experiment Satellite (TES), Germany’s Bird and Belgium’s Proba. Now PSLV is slated to launch an Italian built satellite and a micro satellite payload of the Singapore based Nanyang Technological University (NTU).
A Deep Space Network will be set up at Bangalore to support the Chandrayaan-1 mission and also to receive data collected by its onboard scientific instruments. A National Science Data Centre to process raw data into user-friendly format will also be located at a suitable place.
The Rs.3800-million Chandrayaan-1 mission is being viewed by ISRO as a stepping stone to far more ambitious space projects in the years to come including landing a robot on the lunar surface and visits by the Indian spacecraft to other planets of the solar system.
According to Dr. K.Kasturirangan, former chairman of ISRO and currently a Member of Parliament, who had played a key role in giving a concrete shape to the Chandrayaan-1 project, India should play a pre-eminent role in the international efforts to push back the boundaries of the ‘final frontiers.’
ISRO has already made it clear that the Indian lunar mission will not be an exercise in reinventing the wheel. Chandrayaan-1 will strive to unravel the hitherto unknown features of the moon for the first time. Moreover, Dr. Nair points out that a lunar mission can provide impetus to science in India, a challenge to technology and possibly a new dimension to international cooperation.
The scientific objectives of Chandrayaan-1 include preparation of the three dimensional atlas of the regions on the moon and the chemical mapping of the entire lunar surface.
ISRO is serious about the potential availability of water on the moon. The
Indian scientific community is of view that the availability of water—essential to sustain life—could fuel an international race to reinvestigate the moon from fresh perspective.
Similarly, the abundant availability of helium, a clean source of energy, is yet another attraction to probe the moon. Scientific community in India is clear that an area that needs to be pursued seriously is the mining of helium and bringing it back to the earth for power generation.
More than three decades ago, Dr.Vikram Sarabhai, the architect of the Indian space programme outlined what he considered should be India’s objectives in space. “We don’t have the fantasy of competing with the economically advanced nations in the exploration of the moon or manned flights. But we are convinced that to play a meaningful role nationally and in the community of the nations, we must be second to none in the application of advanced technologies to the real problem of man and society which we find in our country.”
But then, in the context of the rapid strides made by India in computer programming, nuclear energy and stem cell research, the lunar probe is but a reflection of the nation’s will.
links:http://www.the-south-asian.com/Sep2004/indias_moon_mission.htm
