Synthetic Aperture Radar

Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic Aperture Radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. Synthetic aperture radar complements photographic and other optical imaging capabilities because of the minimum constraints on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies.

Synthetic aperture radar technology has provided terrain structural information to geologists for mineral exploration, oil spill boundaries on water to environmentalists, sea state and ice hazard maps to navigators, and reconnaissance and targeting information to military operations. There are many other applications or potential applications. Some of these, particularly civilian, have not yet been adequately explored because lower cost electronics are just beginning to make SAR technology economical for smaller scale uses.

Sandia has a long history in the development of the components and technologies applicable to Synthetic Aperture Radar — 40 years in radar, antenna, and miniature electronics development; 30 years in microelectronics; and 25 years in precision navigation, guidance, and digital-signal processing. Over the last decade, we have applied these technologies to imaging radars to meet the needs of advanced weapon systems; verification and nonproliferation programs; and environmental applications. Sandia’s expertise in electromagnetics, microwave electronics, high-speed signal processing, and high performance computing and navigation, guidance and control have established us as world leaders in real-time imaging, miniaturization, processing algorithms, and innovative applications for SAR.

How does Synthetic Aperture Radar work?

A detailed description of the theory of operation of SAR is complex and beyond the scope of this document. Instead, this page is intended to give the reader an intuitive feel for how synthetic aperture radar works.

Consider an airborne SAR imaging perpendicular to the aircraft velocity as shown in the figure below. Typically, SARs produce a two-dimensional (2-D) image. One dimension in the image is called range (or cross track) and is a measure of the “line-of-sight” distance from the radar to the target. Range measurement and resolution are achieved in synthetic aperture radar in the same manner as most other radars: Range is determined by precisely measuring the time from transmission of a pulse to receiving the echo from a target and, in the simplest SAR, range resolution is determined by the transmitted pulse width, i.e. narrow pulses yield fine range resolution.

Synthetic Aperture Radar Imaging Concept

The other dimension is called azimuth (or along track) and is perpendicular to range. It is the ability of SAR to produce relatively fine azimuth resolution that differentiates it from other radars. To obtain fine azimuth resolution, a physically large antenna is needed to focus the transmitted and received energy into a sharp beam. The sharpness of the beam defines the azimuth resolution. Similarly, optical systems, such as telescopes, require large apertures (mirrors or lenses which are analogous to the radar antenna) to obtain fine imaging resolution. Since SARs are much lower in frequency than optical systems, even moderate SAR resolutions require an antenna physically larger than can be practically carried by an airborne platform: antenna lengths several hundred meters long are often required. However, an airborne radar could collect data while flying this distance and then process the data as if it came from a physically long antenna. The distance the aircraft flies in synthesizing the antenna is known as the synthetic aperture. A narrow synthetic beamwidth results from the relatively long synthetic aperture, which yields finer resolution than is possible from a smaller physical antenna.

Achieving fine azimuth resolution may also be described from a doppler processing viewpoint. A target’s position along the flight path determines the doppler frequency of its echoes: Targets ahead of the aircraft produce a positive doppler offset; targets behind the aircraft produce a negative offset. As the aircraft flies a distance (the synthetic aperture), echoes are resolved into a number of doppler frequencies. The target’s doppler frequency determines its azimuth position.

While this section attempts to provide an intuitive understanding, SARs are not as simple as described above. Transmitting short pulses to provide range resolution is generally not practical. Typically, longer pulses with wide-bandwidth modulation are transmitted which complicates the range processing but decreases the peak power requirements on the transmitter. For even moderate azimuth resolutions, a target’s range to each location on the synthetic aperture changes along the synthetic aperture. The energy reflected from the target must be “mathematically focused” to compensate for the range dependence across the aperture prior to image formation. Additionally, for fine-resolution systems, the range and azimuth processing is coupled (dependent on each other) which also greatly increases the computational processing.

source:http://www.sandia.gov

ISRO joins big league in space

Indian space agency continues its successful run, this week it placed in orbit an Israeli spy satellite launched under a commercial contract.

This has propelled the Indian Space Research Organization or ISRO into the big league and its now well poised to enter the US$ 15 billion a year global launch market, Indian satellite images are already popular.

The commercial arm of ISRO the Antrix Corporation has meanwhile been doing brisk business with its total turnover for the last fiscal rising to Rupees 664 crores. ISRO is all set to rake in the money while travelling to Moon, Mars and Beyond.

The twenty fifth launch of a rocket from the Indian space port, a significant milestone in more ways than one.

The Polar Satellite Launch Vehicle or the PSLV placed an Israeli spy satellite TecSAR in orbit on Monday.

This is ISRO’s second fully commercial launch and even though they are not saying how much Israel paid them. Sources said that it is higher than the market rate of 20,000 dollar or 8 lakh rupees per kg. The TecSAR weighs about 300 kg.

For its first commercial launch., the 352 kg Italian satellite Agile. ISRO had charged 11 million dollars or 44 crore rupees. That too was well above the market rate.

PSLV is popular because its considered reliable and the launch site is close to the equator giving the necessary edge.

”People have realized that the PSLV is a real workhorse based on its reliability and cost effectiveness,” said Dr G Madhavan Nair, Chairman, ISRO.

Now, the Indian space agency gets 75 per cent of its business from foreign clients.

ISRO’s commercial arm, Antrix Corporation has increased its turnover by 50 per cent this fiscal, earning almost 664 crore rupees.

ISRO has contracts for launching four small satellites for Singapore, Netherlands, Canada and Germany.

And the agency has also won a contract for making two large communications satellites for European customers.

It is not just ISRO’s hardware that is in demand, but the images taken by Indian Remote sensing satellites are much in demand in the international market.

The international experts are all praise for ISRO.

”Indian Space Organisation is good, and more important than the facilities it is the quality of the engineers and scientists and the technicians. They have a great capability,” said Dr Michael Griffin, Administrator, NASA, USA to NDTV.

On being asked that whether India is ready to go moon and beyond, he replied, ”Absolutely. India has the technical capability and will soon prove it to send an unmanned scientific spacecraft to the moon.”

”And frankly India has the intrinsic capability to, within quite a few years to be conducting human space flights if they wish to do so,” he added.

India is today a force to reckon with among the comity of space faring nations, with 11 communications satellites in orbit, the largest domestic constellation in all of Asia Pacific and with seven remote sensing satellites in space India today can map at resolution less then a meter. ISRO can now truly dream big.

source:http://www.ndtv.com

Putting the villages on the map in DR Congo

Hundreds of villagers are helping to map parts of the Democratic Republic of Congo where thick forest and conflict have prevented effective mapping.

So far about 190 villages have been found in one area of Bandundu province where old maps show only 30, UK-based charity The Rainforest Foundation says.

Most maps are produced from satellite images taken from above, but this project is using handheld GPS units. The map is intended to aid post-war planning and timber permit allocations.

A five-year conflict in DR Congo ended in 2003.

Resource-rich
“In one of the sectors of the territory that the groups are mapping at the moment, there are something like 190 villages, but on the official map there are about 30,” Cath Long of the Rainforest Foundation which is organising the project told the BBC’s Network Africa.

She said millions of Congolese depend on the forest for their existence.

“The real worry is that permits to cut timber, permits to extract resources will be given to external companies without recognising the fact that people are already there and already using the forest,” she said.

The charity hopes the map will be ready for a government meeting in May on forest and land.

The government has already allocated parts of the territory to 11 logging concessions, it says.

DR Congo is home to one of the word’s largest rainforests and has huge reserves of gold, diamonds, copper and coltan, used to make mobile phones.

Correspondents say these riches have been a key factor in the civil wars, instability and bad government the country has known since independence.

Source : http://news.bbc.co.uk/

RADAR AND MICROWAVE REMOTE SENSING

Electromagnetic radiation at long wavelengths (0.1 to 30 centimeters) falls into a segment of the spectrum commonly called the microwave region. At still longer wavelengths (centimeters to meters) the radiation is known as radio waves (these can be generated by manmade transmitters or occur naturally [e.g., beamed from energetic stars]). Remote sensing has utilized passive microwaves, emanating from thermally activated bodies. But, in much more common use (since World War II) is another manmade device, radar, an active (transmitter-produced) microwave system that sends out radiation, some of which is reflected back to a receiver. The varying signal, which changes with the positions and shapes of target bodies, and is influenced by their properties, can be used to form kinds of images that superficially resemble those recorded by Landsat-like sensors. This first page introduces certain basic principles, describes the common radar bands in use, and shows a typical radar image.

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Radar Defined

Radar is an acronym for Radio Detection and Ranging. Radar is an active sensor systems. It generates its own illumination as an outgoing signal that interacts with the target such that some of the signal is returned as backscatter that is picked up by the same antenna that emitted the radar beam. Radar operates in part of the microwave region of the electromagnetic spectrum, specifically in the frequency interval from 40,000 to 300 megahertz (MHz). The latter frequency extends into the higher frequencies of the broadcast-radio region. Commonly used frequencies and their corresponding wavelengths are specified by a band nomenclature, as follows:

• Ka Band: Frequncy 40,000-26,000 MHz; Wavelength (0.8-1.1 cm)

• K Band: 26,500-18,500 MHz; (1.1-1.7 cm)

• X Band: 12,500-8,000 MHz; (2.4-3.8 cm)

• C Band: 8,000-4,000 MHz; (3.8-7.5 cm)

• L Band: 2,000-1,000 MHz; (15.0-30.0 cm)

• P Band: 1,000- 300 MHz; (30.0-100.0 cm)

This chart summarizes the above information on Bands in the Microwave segment of the EM Spectrum:

Unlike other sensors that passively sense radiation from targets illuminated by the Sun or thermal sources, radar generates its own illumination (hence, it is active; another example is the flash camera) by sending bursts or pulses of EM energy that reflect off of a target. A fraction of the reflected energy then returns to the radar’s receiving antenna, which collects it and passes it to an electronic processing system. A radar system is a ranging device that measures distances as a function of round trip travel times (at light speed) of a directed beam of pulses (the signal, whose strength is measured in decibels, dB) spread out over specific distances. In this way radar determines the direction and distance from the instrument (fixed or moving) to an energy-scattering object. We can also derive information about target shapes and certain diagnostic physical properties of materials at and just below the surface, or from within the atmosphere, by analyzing signal modifications.

8-1: In the Introduction, you learned that wavelength times frequency = the speed of light. By choosing the proper units, this equation can be derived: Wavelength (in cm) = 30/frequency (in GHz or 10⁹cycles per second). Given a frequency of 20 GHz, what Wave Band would this radar pulse fall into? ANSWER

By supplying its own illumination, radar can function day and night and, for some wavelengths, without significant interference from blocking atmospheric conditions (e.g., clouds). These characteristics prompted radar development in World War II for tracking (attacking) aircraft and ships. Ground (fixed) and airborne (mobile) radar systems are used extensively today for marine navigation and air traffic control. Imaging radar, mounted on air or space platforms, has proven especially useful in mapping cloud-shrouded land surfaces (a landforms map of Panama used this approach). This use also permits expressing surface shapes in regions heavily covered by vegetation (penetrated by some bands).

8-2:Why did radar play such a vital role in the Allies’ victory over Germany in World War II? ANSWER

As we shall see in this Section, radar has become increasingly important in various applications of remote sensing. The military continues to be a prime user. Several satellites operating now have radar has their principal sensor. Most of us are most familiar with radar’s use in Meteorology, mainly as a tracker of storms, rainfall, and advancing fronts. We will skip further reference to this last use in this Section; it is defered until Section 14 that deals with Meteorological Remote Sensing.

This ability to mirror ground surfaces for displaying topography is a prime use of radar for a variety of applications. Some radars operate on moving platforms; others are fixed on the ground. The usefulness in determining land surface configurations is strikingly confirmed in the radar image strip (SIR-A system on the Shuttle) shown here, extending 300 km (200 mi) to the northeast (right side) across the folded and dissected South American Andes in Bolivia. The image covers from the high plains (Altiplano) on the west to the lowlands (Amazon Basin) on the east. (Scroll to see this right end.)

8-3: Care to guess why the Low plains are dark and the High (Alti) plains are light.

Radar systems, as well as passive sensors operating at microwave wavelengths (slightly shorter than radar), are also effective in detecting soil moisture, storms-clouds-rain, and sea states.

source:http://rst.gsfc.nasa.gov

Imagery for Everyone

RESTON, VA – The USGS Landsat archive is an unequalled 35-year record of the Earth’s surface that is valuable for a broad range of uses, ranging from climate change science to forest management to emergency response, plus countless other user applications. Under a transition toward a National Land Imaging Program sponsored by the Secretary of the Interior, the USGS is pursuing an aggressive schedule to provide users with electronic access to any Landsat scene held in the USGS-managed national archive of global scenes dating back to Landsat 1, launched in 1972. By February 2009, any archive scene selected by a user – with no restriction on cloud cover – will be processed automatically to a standard product recipe, using such parameters as the Universe Transverse Mercator projection, and staged for electronic retrieval.

In addition, newly acquired scenes meeting a cloud cover threshold of 20% or below will be processed to the standard recipe and placed on line for at least three months, after which they will remain available for selection from the archive.

Newly acquired, minimally cloudy Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data covering North America and Africa are already being distributed by the USGS over the Internet at no charge, with expansion to full global coverage of incoming Landsat 7 data to be completed by July 2008 (see timeline below). The full archive of historical Landsat 7 ETM+ data acquired by the USGS since launch in 1999 will become available for selection and downloading by the end of September 2008. At that time, all Landsat 7 data purchasing options from the USGS, wherein users pay for on-demand processing to various parameters will be discontinued.

By the end of December of 2008, both incoming Landsat 5 Thematic Mapper (TM) data and all Landsat 5 TM data acquired by the USGS since launch (1984) will become available, with all Landsat 4 TM (1982-1985) and Landsat 1-5 Multi-Spectral Scanner (MSS) (1972-1994) data becoming available by the end of January 2009. All Landsat data purchasing options from the USGS will be discontinued by February 2009, once the entire Landsat archive can be accessed at no charge.

Landsat scenes can be previewed and downloaded using the USGS Global Visualization Viewer at http://glovis.usgs.gov [under “Select Collection” choose Landsat archive: L7 SLC-off (2003-present)]. Scenes can also be selected using the USGS Earth Explorer tool at http://earthexplorer.usgs.gov [under “Select Your Dataset” choose Landsat Archive: L7 SLC-off (2003-present)]. For further information on Landsat satellites and products, see http://landsat.usgs.gov

Source : http://landsat.usgs.gov/

How Planktons affect Climate Change

Some of the smallest living organisms feed the largest animals. Plankton are the food supply of many marine creatures including the largest fish, the whale shark and the largest mammal, the blue whale.

Plankton are organisms that float drift around oceans, seas and other bodies of water; plankton derive their name from the Greek “planktos” which means “drifter”. These high water drifters are both plants and animals (jellyfish are plankton). The plankton plants use chlorophyll to convert energy from light into carbohydrates, soaking up carbon dioxide dissolved in water as part of the process. The animal plankton eat other animals.

Plankton are important both in terms of their impact on ecosystems and in terms of the carbon dioxide that they soak up and convert. Scientists at the IMF-GEOMAR Institute in Kiel Germany have been trying to understand what will happen in the ocean if the climate warms up.

Oceans soak up more human made carbon dioxide than any other thing and plankton, because they use dissolved carbon dioxide, enable the ocean to continue this carbon sink effect. It is thought that oceans soak up half of the human made carbon dioxide. Ocean plankton have been ignored in most climate change models until now, so the work at Kiel is important to our overall understanding of climate change processes.

There are positives and negatives from the study. The positive is that more carbon dioxide means that the plankton will prosper and in doing so will soak up more and more of the carbon emissions we pump into the atmosphere.

The negative is that increased uptake of carbon dioxide will probably cause the oceans to become more acidic. This will reduce the amount of food in the oceans that ocean inhabitants eat.

Experiments showed that higher carbon dioxide levels gave a large boost to numbers of plankton. It showed itself in a big algae bloom which then sunk to the bottom of the sea, making way for the upper part of the sea to absorb more carbon dioxide. Good.

When the deceased plankton arrived at the bottom of the ocean (or in the case of the experiment the bottom of a 27 metre tank) the decomposition of the plankton soaked up oxygen and created more acidic water. Bad.

When plankton grow they emit dimethyl sulphide, which helps in the formation of clouds. Some think that increased cloud formation would protect the planet from radiation which then it is thought would reduce the impact of climate change. I am not so sure that messing about with the weather is right.

There will be consequences that we are not wise enough o compute or understand. While all this science is debating, plankton are prospering. Large masses of jellyfish are being reported in many sea side resorts.

There have always been jelly fish, but some resorts in Australia are experiencing problems with poisonous box jellyfish which for hundreds of years were unknown in those waters. Box jellyfish were once only found on the southern (windward) side of the Hawaiian island of Oahu; now they found on the on the northern and western coasts.

This may be evidence of a shift in the ocean currents but what seems to be without doubt is that there are more jellyfish than before and this is probably due to there being warmer seas and a higher availability of carbon dioxide.

Back home in Britain the North Sea has higher levels of jellyfish. This is affecting birds that eat fish. Guillemot numbers in Shetland have been devastated, Great Skuas on Foula have not bred well, and this has been explained by there being less sand eels (a small silver fish that sea birds eat) in the North Sea. Historically this part of the North Sea has been a little to cold to support jellyfish, and the effect of climate change on the northern part of the planet is greater than on the equatorial region.

Now although plankton are prospering for now there is, so as to speak, a sting in the tail. Plankton that have skeletons cannot manufacture the calcium carbonate that they need for the skeletons in acidic waters, and acidic waters are a by product of too many plankton. In the Southern Antarctic Ocean lives an animal plankton called pteropod – which are snail like. Scientists think that its shells will not be able to withstand the acidic sea that is likely to exist by the end of this century; once you take out an important element in an ecosystem you never quite know how it will impact on the rest of the system and the impact is usually less than benign.

There is yet another sting that plankton may well deliver; I have explained how it uses carbon dioxide, but plankton also respire, emitting carbon dioxide. Until now they absorb far more carbon dioxide than they emit.

A team of scientists led by Angel López-Urrutia of the Spanish Institute of Oceanography in Gijón have some evidence that the balance between production and respiration of plankton is affected by temperature. Apparently while the rates of photosynthesis and respiration in plankton both rise with temperature, the rate of respiration goes up faster, so that the plankton will emit more carbon than they soak up.

As plankton are thought to soak up half of the human made carbon dioxide the oceans instead of becoming a carbon store may end up as a carbon emitter.

source:http://robertkyriakides.wordpress.com

ISRO Launch Perfect:PSLV-C9 launched successfully with 10 satellites

Setting a world record, India’s Polar rocket on Monday successfully placed ten satellites, including the country’s remote sensing satellite, into orbit in a single mission.

The ten-pack launch of the Indian Space Research Organisation saw the 230-tonne Polar Satellite launch Vehicle carry the heaviest luggage–824 kgs–and put into orbit an Indian Mini Satellite and eight foreign nano satellites besides the Cartosat-2A remote sensing satellite.

At the end of the 52-hour countdown, the PSLV-C9, with a lift-off mass of 230 tonne, blasted off from the launch pad at the Satish Dhawan Space Centre and soared into the clear sky in a textbook launch at 9:23 am.

Fourteen minutes after lift off, the fourth stage of the ISRO’s workhorse launch vehicle, in its 13th flight, injected the ten satellites, into the 635 km polar Sun Synchronous Orbit.

This is for the first time that ISRO has put ten satellites in orbit in a single launch. This is also the PSLV’s twelfth successful flight.

It is for the first time in the world that ten satellites were launched in a single mission. Russia [Images] had earlier launched eight satellites together.

Besides the 690 kg Indian remote sensing satellite CARTOSAT-2A and the 83 kg Indian Mini Satellite, the rest eight Nano Satellites were from abroad.

This is the third time that the PSLV has been launched in the core alone version, without the six solid propellant first stage strap-on motors.

Terming the launch satisfactory, ISRO Chairman G Madhavan [Images] Nair said, “All parameters worked wonderfully well.”

“It is a proud moment for ISRO as it put 10 satellites into the orbit in a single launch and I am extremely proud of the entire team,” Nair said.

He said that initially there was some anxiety about the weather conditions but everything went well.

Mission Director Dr Kosy said the launch proved that the PSLV was dependable and capable. “This has proven that the PSLV can be depended upon and that puts more responsibilities for us in the upcoming Chandrayan mission,” Kosy said.

CARTOSAT-2A, which was put in orbit by PSLV-C9, is the latest state-of-the-art remote sensing satellite weighing 690 kg, carries a Panchromatic Camera capable of taking black and white pictures in the visible region of electromagnetic spectrum. It would be used for mapping purpose and management of natural resources.

The IMS-I, developed by ISRO for a remote sensing, has two optical payloads–a mutispectral camera (Mx Payload) and a Hyperspectral Camera (HySI Payload), which would operate in the visible and near infrared regions of the electromagnetic spectrum.

The eight Nano Satellites, built by universities and research institutions in Canada [Images] and Germany [Images], were launched under a commercial agreement.

The satellites, with a total weight of appriximately 50 kg, were built to develop nanotechnologies for use in satellites and for the development of technologies for satellite applications.

source:http://www.rediff.com

Russia launches European navigation satellite

Moscow (PTI): Russia on Sunday launched the second European navigation satellite, which will be part of the projected navigation system to be operated by the European space agency.

Galileo GIOVE-B satellite was launched from the Russian-leased Baikonur cosmodrome in Kazakhstan with the help of Soyuz-FG launch vehicle at 4.16 am (local time).

After the successful deployment in orbit, the controls have been passed on to the European Space Agency (ESA), which is planning to deploy its Galileo global positioning system by 2013, according to Russian TV channel ‘Vesti’.

Franco Bonacina, the ESA spokesman, was also quoted as having described the mission as successful.

A similar satellite GIOVE-A was also lunched by Russia in December 2005. The satellite has Passive Hydrogen Maser PHM or popularly known as ‘atomic clock’, for precision time display.

After its completion in 2013 with 30 satellites in orbit Galileo will become the world’s third space-based navigational system after the US’ Global Positioning Satellite (GPS) and Russian GLONASS.

The European Parliament on Wednesday gave approval to the long-delayed Galileo project, which is aimed at challenging the GPS’ dominance.

source:http://www.hinduonnet.com

Future Geographies: Global warming and Regional Temperature Patterns

An enhanced greenhouse effect caused by human activities will upset the radiation balance of the earth system creating a variety of changes in the geography of planet Earth, the most notable being air temperature. Temperature trends over the past 100-plus years clearly indicate rising temperatures on all continents and over the oceans.

Predicting changes to the the global patterns of temperature is a challenging undertaking for scientists as they must rely on models for their forecasts. The models are numerical representations based on how our earth system functions. They are limited by our understanding of earth system processes and long-term data sets. Using a variety of models, geoscientists have forecast a range of possible scenarios. One thing is clear from their predictions, that the amount of temperature change varies geographically.

Figure AT.8 Projected future regional patterns of warming based on three emissions scenarios (low, medium, and high growth). Source: NASA Earth Observatory, based on IPCC Fourth Assessment Report (2007)

Arctic regions

The arctic regions appear to be impacted the most. Observations of mean annual surface air temperature over the past 50 years has increased 3.6^oF to 5.4°F in Alaska and Siberia and decreased by 1.8°F over southern Greenland. Mean annual surface air temperature over the Arctic region (north of 60° latitude) is projected to increase 3.6°F by 2050 and 8°F by 2100.

The Midlatitudes

Climate change is expected to increase the frequency of extreme events in midlatitude regions like the midwest United States. A severe drought in 1988, heat waves in 1995 and 1996, flooding on the Mississippi in 1993 (100-year flood) and 2002, and numerous tornadoes and severe thunderstorms can be expected in the future. Illinois will be become warmer, especially in the summer having temperatures more like present-day Oklahoma or Arkansas (http://go.ucsusa.org/greatlakes/glregionill.html) Wisconsin temperatures could rise 5^o-10^oF in the winter and by 8^o - 17^o F during the summer by 2100. Extreme heat will be more common than today. Southern Ontario’s winter temperatures are expected to increase by 3^o - 7^oC and summer’s to be 4-8C warmer. More southerly states like Illinois will experience less warmer. Winter temperatures are expected t increase by 5^o-7F during the winter in Indiana and summer temperatures increasing by 8^o - 10^o F. Growing seasons could be 4 to 7 weeks longer in Wisconsin and 3 to 6 weeks longer to the south in Illinois. Under a medium-high emissions scenario, the IPCC predicts a 5.5^o-7.9^oF change in statewide in California.

Subtropical Regions

Though most geoscientists have felt that the Arctic will show the first true signs of a future climate, dramatic changes have been recorded in subtropical regions. Recent analysis of satellite data has fuond that each hemisphere’s jet stream has moved poleward by about 1 degres of latitude or 70 miles. Jet streams are found on the poleward limit of the tropics which means they are getting wider. Coninued movement would mean the spread of subtropical deserts like the Sahara. Regional climate predictions for southern Africa during summer suggest a warm season increase of 2^oC to 4^oC over the subcontinent, with the doubling of carbon dioxide. Current climate models project regional temperature increases between 4^o and 10^o F by 2100, with an 8^o to 15^oF increase in the average summer heat index for the southeastern United States.

Tropical Regions

Most model predictions indicate the smallest change to temperature will occur in tropical latitudes. Depending on model assumptions and location, annual changes on the order of .1 ^oC to 3 ^oC are predicted. Analysis indicates that there may be significant differences within the tropics, especially in Asia, depending on proximity to the sea. Warming is projected to be least in the islands and coastal areas throughout Indonesia, the Philippines, and coastal south Asia and Indo-China and greatest inland. Even with relatively small temperatures, they can be devastating. A 3-degree Celsius (5.4 Fahrenheit) rise in temperature would result in a 60 percent reduction in the arabica coffee area in Brazil, the world’s largest producer.

source:http://www.uwsp.edu

Arctic ice melting faster than predicted: WWF

Arctic sea ice is melting “significantly faster” than predicted and is approaching a point of no return, conservation group the World Wildlife Fund (WWF) warned in a new study released on Wednesday.

The volumes of the Greenland Ice Sheet and ice in the Arctic Ocean were estimated at 2.9 million and 4.4 million cubic metres respectively in September 2007, the lowest ever levels recorded, the organisation said.

The sea ice shrank to 39 per cent below its 1979-2000 mean volume, it said. “Recently observed changes are happening at rates significantly faster than predicted” by the 2005 Arctic Climate Impact Assessment (ACIA) and last year’s report by the Intergovernmental Panel on Climate Change (IPCC), WWF said.

The melting of arctic sea ice and the Greenland Ice Sheet was happening so fast that experts were now questioning whether the situation is close to “tipping point,” where sudden and possibly irreversible change takes place.

“When you look in detail at the science behind the recent Arctic changes it becomes painfully clear how our understanding of climate impacts lags behind the changes that we are already seeing in the Arctic,” said Martin Sommerkorn, one of the authors of the report.

The WWF will present its report, comprised of the latest research in the region, to the meeting on Thursday of the Arctic Council, which groups Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden, and the United States.

The conservation group’s researchers also warned of the devastating effect the rapid melting of the arctic ice could have on polar bears in Canada, where two thirds of the world’s population of the animals live.

“Previous models had predicted that melting sea ice would mean some polar bear populations could become extinct by 2050. The new evidence points to even earlier regional extinctions,” said Peter Ewins, director of species conservation at WWF-Canada.

The Committee on the Status of Endangered Wildlife in Canada will present the government with its estimates of the status of polar bears there on Friday.

source:http://timesofindia.indiatimes.com