Category: Earth Observation

Usually the North Sea conjures up cold and gloomy visions. But as the stunning image above shows, this isn’t always the case. ESA’s Envisat captured vast green swirls of phytoplankton bloom drifting in the North Sea currents on May 7th 2008; spring has most definitely sprung for the Scottish waters. But how is this bright green bloom produced? What has stirred up all this activity? It seems that for a short time, the lush green landscape of Fife is matched by the sea-faring plankton off the UK coast…

This vivid green bloom was created by a type of plankton called phytoplankton. The microscopic plant floats near the surface of large bodies of water where sunlight is plentiful. Like any land-based plant, phytoplankton requires photosynthesis to survive. Other types of plankton include zooplankton (microscopic creatures) and bacterioplankton (water-borne bacteria) survive by feeding off other plankton varieties. The plant variety of plankton, phytoplankton, is well known to produce blooms when nutrients on the marine environment increase, boosting phytoplankton population. It would seem that the water off the Scotland coast has become particularly nutrient rich, with plenty of sunlight, creating magnificent displays observable from orbit.

This particular bloom was captured by the Medium Resolution Imaging Spectrometer (MERIS) instrument on board the ESA’s Envisat operating at a full spatial resolution of 300m (i.e. features of 300m can be resolved). The green hue is from the chlorophyll (essential for photosynthesis) contained within each phytoplankton cell. Depending on the phytoplankton species, it’s possible that there are hundreds to thousands of cells per millilitre of sea water.

Phytoplankton is very important when considering the concentrations of carbon dioxide in the atmosphere and their density in the worlds oceans are modelled in simulations of future climate change. During photosynthesis, they absorb carbon dioxide (and generate oxygen), so they form a highly influential carbon sink.

Source: ESA Picture of the Day

Some of the first satellite images have been released of areas in China hit by the 7.9 magnitude earthquake on May 12, 2008. This image shows Beichuan, one of the worst-hit areas in Sichuan Province of southwest China. The pictures reveal a large forest, a school and clusters of residential houses along a river that has been destroyed out by the quake. A road along the river was also severely damaged. The images were taken by Taiwan’s FORMOSAT-2 satellite. A “before” image is also available, taken in two years ago in May of 2006:

The pictures are expected to be used as references in China’s efforts in searching and rescuing people still missing in Sichuan.

Harry Chang, a professor of National Taiwan Normal University said the images have been given to the Chinese Academy of Sciences. Chang said that in Beichuan, the earthquake also caused landslides, evident in the top photo, covering some 1,500 hectares (3,705 acres), which had blocked the river.

“Accordingly, several new lakes have been formed. What is dangerous is that should the new lakes burst, the residents living in the low-lying areas of the river would be in danger,” he said.

Chang also warned of mudslides caused by rain, saying “it would make the rescue work more difficult.” As of May 15, officials estimated the death toll could reach 50,000.

Monday’s earthquake began at 2:28 p.m. local time (06:28 UTC). The quake was felt throughout much of China, as well as parts of Taiwan, Thailand, and Vietnam. This elevation map above shows the region where the earthquake struck. Green indicates the lowest elevations, and beige the highest. The data for this map were collected by NASA’s Shuttle Radar Topography Mission (SRTM) in 2000. Overlain onto the map are earthquake magnitude indicators. The earthquake’s epicenter was approximately 90 kilometers (55 miles) west-northwest of the city of Chengdu. Smaller magnitude events occurred northeast of the epicenter, and generally followed the edge of the Longmen Shan mountain range.

Original News Sources: The China Post, NASA Earth Observatory

The cyclone that ravaged the southeast Asian country of Myanmar over the weekend was an incredibly deadly and destructive storm. News reports say at least 10,000 people were killed, and thousands more were missing as of May 5. Cyclone Nargis made landfall with sustained winds of 130 mph and gusts of 150-160 mph, which is the equivalent of a strong Category 3 or minimal Category 4 hurricane. This was the first cyclone of the 2008 season. Above is an image from NASA’s Terra satellite, and specifically the Moderate Resolution Imaging Spectroradiometer (MODIS.) You can see this storm was a whopper, however, by the time MODIS acquired this image on May 3 at 10:55 am local time the cyclone had lost much of its original strength and was at tropical storm strength. Even more astounding are the images available from MODIS of the landscape of Myanmar both before and after the cyclone hit.


The top image was taken on April 15, 2008, well before the storm and shows a calm landscape where rivers and lakes are visible, as well as the green of vegetation. In the lower image, taken on May 5, the entire coastal plain is flooded. News reports say the agricultural areas have been especially hard hit. But cities as well were affected. For example, Rangôn, with a population over 4 million is almost completely surrounded by floods. Several other large cities with populations of 100,000–500,000 are also in the area affected by the cyclone.

The MODIS Rapid Response Team has been processing the images as soon as they are available from the spacecraft in order to provide information about the storm and the region.

The blue dot on the globe below marks the Andaman Sea and the area affected by Cyclone Nargis.

Original News Source: NASA’s Earth Observatory

You only have to walk outside at night, look up and not see the Milky Way to know that light pollution is a problem. And seen from space at night, the Earth’s surface glows with the light of millions of homes, buildings, cars and streetlights. Seen at night, our impact on the Earth is immediate and obvious.

A few years ago, NASA and NOAA compiled a complete world map of the nighttime Earth, using 9 months of data collected by satellites. This “Night Lights” image is pretty famous, and widely circulated around the Internet.

There’s a great article at NASA’s Earth Observatory that describes how they capture these night images of the Earth’s surface. You can also see many of the best images taken so far.

Click here to read the article.

Scientists working at the University of California, Los Angeles (UCLA) have identified the origin behind the upper atmospheric “hiss” that energizes the high-energy particles bouncing around inside Earth’s radioactive Van Allen Belts. This is significant, as this has been a very long wait for answers to the origin of this low-frequency radio wave emission… after 40 years of looking, we may now have an answer…

The Van Allen Belts surrounding Earth can be a terrifying place for spacecraft and astronauts. Occupying a volume 200 km above the surface and can extend as far as seven Earth radii (over 44,000 km). These volumes of highly energetic particles are trapped by the Earth’s magnetosphere, bouncing electrons and protons back and forth in their magnetic prison. The Van Allen Belts are variable and closely related to solar activity. As the solar wind hits the Earth’s magnetosphere, solar wind particles will fall into the polar cusp regions, entering the atmosphere and creating aurorae in Northern and Southern Polar regions (Aurora Borealis and Aurora Australis respectively). However, some particles are fed into the magnetosphere and become trapped between the onion skin-like layers of magnetic field lines and cannot escape.

This is how the Van Allen Belts are supplied, and the population of protons and electrons are expected to increase and become more energetic during solar storms. Although we know a lot about these regions, very little is known how the trapped electrons and protons are energized so much that they can penetrate lead up to 1 mm deep. This has obvious design implications for the thousands of satellites orbiting the Earth, and poses a serious health risk to astronauts spending long periods in space.

In new research published in Nature today, the UCLA research group believe they have found the origin of upper atmospheric “hiss”. The hiss has radio wave frequencies and has been observed since early missions into space in the 1960s. Thought to originate from magnetic interactions in the magnetosphere itself, or even from intense lightning storm emissions into the upper atmosphere, definitive proof for the source of this strange phenomenon was proving very elusive. Putting classical ideas to one side, Jacob Bortnik’s work focuses on a totally different form of electromagnetic wave called “chorus”. This wave was thought to have no connection with radio hiss, but Bortnik proves that chorus waves, travelling many thousands of kilometres, can evolve into the hiss which characterizes the Van Allen Belts.

“Here, we show that a different wave type, called chorus, can propagate into the plasmasphere from tens of thousands of kilometers away and evolve into hiss. Our new model naturally accounts for the observed frequency band of hiss, its incoherent nature, its day-night asymmetry in intensity, its association with solar activity and its spatial distribution. The connection between chorus and hiss is very interesting because chorus is instrumental in the formation of high-energy electrons outside the plasmasphere, while hiss depletes these electrons at lower equatorial altitudes.” – Jacob Bortnik.

The UCLA group were actually not researching the atmospheric hiss, but were working on chorus waves – that typically propagate outside the plasmasphere – and realized they could evolve into the “hiss” responsible for particle energization in the Van Allen Belts.

This research has massive consequences for the prediction of space weather. The conditions of the space between the Sun and Earth is very important when predicting the onset of a solar storm, but the reaction of the Earth’s upper atmosphere is critical when understanding how potentially damaging particles are energized to such a large extent.

Source: Physorg.com