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Satellite Eye on Earth: November and December 2017 - in pictures

This article is more than 6 years old

Winter solstice, night lights and interesting islands are among the images captured by Nasa and the ESA last month

Dust blowing out of the Copper River valley on Alaska’s south coast. The dust plume was likely comprised of fine-grained loess, which was formed as glacial ice moved over the area and ground the underlying rock into a powder. Dust storms in southern Alaska generally occur in late autumn, when river levels are relatively low, snow has not yet fallen, and the layers of dried, loess-rich mud are exposed to the wind. The Copper River - named for ore deposits found upstream - drains an area of more than 24,000 square miles (62,000 square kilometres) and is, by volume of discharge, the 10th largest river in the United States. Its delta forms one of the largest and most productive wetlands on the Pacific Coast of North America.

Since 2011, satellite sensors have been collecting data on the brightness of lights — natural and manmade — that shine around the Earth at night. With each orbit, this adds to an ever-growing archive of data that is allowing scientists and geographers to track changes in artificial lights, fishing practices, economic activity, development patterns, the movement of goods and people, and many other research areas in innovative ways and on a global scale. This map offers a few small-scale examples of the sort of changes that can be seen: the map shows where the intensity of light decreased (orange), increased (purple), and stayed the same (white) between 2012 and 2016 in the American midwest.

Smoke from California’s wildfires is drawn northward into an approaching storm system off the US Pacific coast on 11 December. The beige-coloured smoke is visible in the lower-centre portion of this image, while the comma-shaped storm system, known as a mid-latitude cyclone, is seen just to the west. Southerly winds ahead of the storm are pushing wildfire smoke several hundred miles northward, parallel to the coastline.

Lake Chad.
Credits: Corona/NASA and Landsat 8/NASA

Lake Chad sustains people, animals, fishing, irrigation, and economic activity in west-central Africa. But in the past half century, the once-great lake has lost most of its water and now spans less than a tenth of the area it covered in the 1960s. Scientists and resource managers are concerned about the dramatic loss of fresh water that is the lifeblood of more than 30 million people.

Extreme swings in Lake Chad’s water levels are not new. The lake has experienced wet and dry periods for thousands of years, according to research. More recently, variations in depth and extent were noted by French explorer Jean Tilho, who reported in 1910 that parts of the lake had dried up. But what is new is the way researchers are studying changes in the lake.

The combination of visible and infrared light helps to better differentiate between vegetation (red) and water (blue and slate grey). These photographs were captured by the Corona spy satellite in 1963 and by an astronaut on the International Space Station in 2015.

In the South Pacific Ocean, part of Fiji’s largest island, Viti Levu, is fringed with coral reefs. Shaped by volcanic activity and earthquakes, the centre of the island contains forests and a mountain range. The highest peak, Mount Tomanivi, reaches more than 1,320m and is located on the central-right side of the image. While the area east of the mountain range receives heavy rainfall, the west side pictured here is in the “rain shadow”, meaning that the mountains block the rain clouds, leaving this area drier than the east. In addition to the human population of around 600,000, lives one of the largest insect species: the giant Fijian long-horned beetle. The island is the only known home to the beetle, which grows up to about 15cm long – excluding antennae and legs. With more than 300 islands, the Fijian archipelago’s low-lying coastal areas are at risk of sea-level rise – a devastating consequence of climate change.

Tropical storm Ockhi brought heavy rain to the west coast of India in early December 2017, stirring up dust plumes and disturbing stagnant, smoggy air in the interior. To the north and west in the image, streams of airborne dust and sand blew out over the Arabian Sea from Pakistan and Iran. The outer bands of Ockhi stretched far to the north, and the system likely strengthened the pressure gradient between the cyclone and a high-pressure system to the north-west, intensifying surface winds until they picked up dust. At the time of the image, sustained winds were estimated to be 50mph (80kph). Ockhi was the strongest cyclone to develop in the Arabian Sea since 2015. It formed near southern India and Sri Lanka on 30 November, moved out over the Arabian Sea, intensified to category three strength on December 2–3, but then weakened quickly as it moved north and closer to land. According to Indian media, the name Ockhi means “eye” in the Bengali language.

Before the opening of the Panama Canal, Cape Horn was a place that gave sailors nightmares. The waters off this rocky point, at the southern tip of Chile’s Tierra del Fuego peninsula, pose a perfect storm of hazards. South-west of Cape Horn, the ocean floor rises sharply from 4,020m to 100m within a few kilometres. This sharp difference, combined with the potent westerly winds that swirl around the “furious fifties”, pushes up massive waves. Combined with frigid water temperatures, rocky coastal shoals, and stray icebergs , it is easy to see why the area is known as a graveyard for ships.

Kutupalong refugee camp, Bangladesh, is inhabited by Rohingya Muslims fleeing persecution in neighbouring Myanmar, and has become one of the densest refugee populations in the world. More than 655,000 Rohingya people have sought refuge in Bangladesh following the outbreak of violence in Rakhine state in August, joining 200,000 other refugees who had already crossed the border. Satellite images collected in the last 12 months clearly show how huts and tents have overtaken the previously vegetated areas.

During October, weak La Niña conditions emerged across most of the central and eastern equatorial Pacific Ocean. The opposite of an El Niño event, La Niña occurs when sea surface temperatures in the central equatorial Pacific are at least 0.5C below average for five consecutive three-month periods. These cooler than normal sea surface temperatures are accompanied by stronger trade winds blowing from east to west, altering weather patterns in the Pacific and around the globe.

The coastal waters along China’s Jiangsu province are brown all year round due to the large volume of suspended sediment that flows out from the Yangtze, Yellow, and other rivers. But every winter, an even larger tongue of sediment emerges over the Great Yangtze Bank and extends hundreds of kilometres into the East China Sea. Some remote sensing scientists argue that the plume is a product of currents moving sediment-laden river water eastward from the coast: others say it is caused by tides lifting up sediment deposited hundreds of years ago.

Autumnal colours on the flanks of Mt Vesuvius, which sits beside the Gulf of Naples in Campania, Italy. It is best known for the eruption in AD79 that buried the Roman cities of Pompeii and Herculaneum. It has hardly been quiet since then, and is the only volcano to have erupted within the last hundred years. Despite this, it is estimated that 3,000,000 people are living nearby - making it the most densely populated volcanic region in the world

City lights of Naples and Campania at night. The Naples region is one of the brightest in the country; roughly 3 million people live in and around this metropolitan area. The different colours of lights in the scene reflect some of the history of development in the area. The green lights are mercury vapour bulbs, an older variety that has been replaced in newer developments by orange sodium bulbs (yellow-orange). To the north-east, the lightless gaps between the homes and businesses are agricultural fields. The bright yellow-orange complex amidst the fields is the CIS emporium, the largest commercial retail facility in Europe. The large black circular area in the photo is Mount Vesuvius.

The coastline of the eastern Mediterranean Sea, including the major population centres of Tel Aviv in Israel, Amman in Jordan, and Beirut in Lebanon. Other light clusters include the Nile Delta in Egypt, and a nearby thin string of lights revealing the Suez Canal. The more scattered lights of the Turkish coastline and the country’s mountainous interior arc from top left to top centre. Few lights appear in vast portions of Saudi Arabia (right), Syria (top centre) and Iraq (top right). Images such as this also show the hints of conflict. In Syria, darkness now reigns along a 300km stretch where lights use to line the Euphrates River in the east of the country.

Part of Lake Winnipeg in the Canadian province of Manitoba, with Reindeer Island visible in the lower-right part of the image. Smaller islands can be seen along the edges of the image, while the swirling shades of green in the waters is an algal bloom. Although algae grows naturally in the lake, high levels of phosphorus seeping into the water from fertilisers and common household products have caused a steady surge of toxic cyanobacteria, or blue–green algae, posing a threat to ecology and human health.

Before and after the mudslide in Freetown, Sierra Leone.

On August 14 2017, more than 1,141 people died and 3,000 people lost their homes in a mudslide near Freetown, Sierra Leone, when a hillside in Regent, a mountainous town 15 miles east of the capital, collapsed in the early hours following heavy rains. Sustained downpours were the immediate trigger for the landslide, but decades of rapid urbanisation in landslide-prone areas, as well as construction along streams where flooding was common, set the stage for the disaster. This pair of images illustrates the extent of the changes: forested areas appear red, urban areas are grey, and landslide debris is tan. In 1986, most of the development was in low-lying, coastal areas. By 2017, development had spread widely into mountainous areas. In addition to the spread of urban areas, the images also highlight the extent of deforestation — one of the factors that helps trigger landslides — to the south of Freetown.

Part of the Atacama Desert in northern Chile, one of the driest places on Earth. In the lower right, the geometric shapes of large evaporation ponds dominate the Salar de Atacama – Chile’s largest salt flat. At about 3,000 sq km, it is the world’s third largest salt flat as well as one of the largest active sources of lithium. From evaporation ponds like the ones pictured here, lithium bicarbonate is isolated from salt brine. Lithium is used in the manufacturing of batteries, and the increasing demand has significantly increased its value in recent years – especially for the production of electric-car batteries.

When viewed from space, the coastline off the coast of Kaş, Turkey, is punctuated by an island that looks remarkably like an exclamation point.

The winter solstice on 21 December marked the longest night of the year in the northern hemisphere and the moment when the it reaches its greatest possible tilt away from the sun.

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