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NASA Earth Observatory
NASA images and stories about climate and the environment.
NASA images and stories about climate and the environment.

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Beating Back the Sands in Isatay

Looking down from space in winter, the patch of earth around Isatay looks greenish brown—a misleading color. This remote part of Kazakhstan—a country with just 8 percent arable land—is far from verdant. In several parts of the country, desertification is a problem, often a result of overgrazing, farming practices, or aggressive land use in this arid climate. The encroaching sands have shaped the landscape around the village of Isatay, just north of the Caspian Sea.

Acquired by the Operational Land Imager (OLI) on Landsat 8, these images show Isatay on February 4, 2017, after a fresh dusting of snow turned the countryside white. The colored patches are sand dunes, which appear darker than they would when the landscape is free of snow. The network pattern on the lower right may be oil rigs, as several large oil and gas pipelines run through the region.

The people of Isatay have been battling the desert for many years. So in 2013, when sand dunes devoured dozens of houses, the villagers did what they had done before: they took up shovels and began to dig away at the mounds of sand covering dwellings, gas pipes, and irrigation trenches. Some of them gave up and moved. But others still hold out hope for an unlikely savior.

That great hope is Haloxylon ammodendron, known as “saksaul” in Russian. The desert-dwelling shrub could help stem the spread of the dunes by anchoring the soil. The haloxylon has a fan of broom-like branches and leaves resembling scales, and it is one of few shrubs that grows in Central Asian deserts.

Between 2008 and 2010, the local government planted haloxylon trees to protect the railroad tracks from being buried by sand. In subsequent years, the leaders of Isatay set aside more than 3 million tenge (roughly $9,000 U.S.) to plant more of the trees.
But even this hardy plant has not taken easily to the terrain, according to local news. It requires water, a scarce resource in the desert. So despite the planting efforts, the desert continues its advance in Isatay and elsewhere in Kazakhstan.
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Fires Threaten Christchurch

Fires near the center of Christchurch, New Zealand, have burned through homes and spurred the evacuation of more than 1,000 people, according to news reports. The seriousness of the Port Hills fires led officials to declare a state of emergency in the Selwyn District and in Christchurch, the largest city on New Zealand’s South Island.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of smoke from the fires at 3:55 p.m. local time on February 16, 2017 (02:55 Universal Time on February 15).

The second and third images show more detailed views of the fire. They were acquired by a multispectral imager on the European Space Agency’s Sentinel-2 satellite at 11:25 a.m. local time on February 14 (22:25 Universal Time on February 13). The first Sentinel image is natural-color (bands 4, 3, and 2) and shows smoke billowing toward the southeast. The third image is false-color (bands 12, 8A, and 4)—a combination of shortwave infrared, near-infrared, and red light. This band combination makes it easier to see actively burning areas (bright red) and burn scars (dark brown).

Christchurch Civil Defense Emergency Management reported on February 17 that the burned area spanned 2,075 hectares (8 square miles) and had a perimeter of 30 kilometers (19 miles). Light rain falling that day was expected to help firefighting efforts. Some areas were being reopened to the public as ground crews completed risk assessments.

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Widespread Snowfall in Afghanistan

In early February 2017, deadly avalanches buried villages in Afghanistan and Pakistan, according to news reports. Snow is not unusual in these countries; there are even glaciers on some of the highest peaks. What is unusual is the amount and extent of the snow. That’s a concern not only for avalanches this winter, but for potential flooding and crop damage when it melts.

These maps show the snow water equivalent (SWE)—the depth of water that would result if the snow were to completely melt—on February 6, 2017 (first map) and February 6, 2016. The darkest blue areas indicate where the snow contained the most water. Turn on the image comparison tool to see the difference between the years. The biggest change appears to be in the foothills of the Hindu Kush mountain range.

Snow water equivalent is calculated by multiplying the snow’s depth by its density. But it’s not always possible to make direct measurements, particularly in remote regions or across large areas. Instead, these maps are the result of a NASA model that simulates snow conditions. It works by combining remotely sensed estimates of precipitation, temperature, radiation, and wind with information about elevation and topography to determine if, when, and how much snow is present. The model also can simulate the snow depth and snow area, which the scientists compare with satellite images captured by the Moderate Resolution Imaging Spectroradiometer (MODIS).

“Snow water equivalent is a useful variable because it allows us to calculate total water volume in a basin,” said Amy McNally, a researcher with the Land Information System at NASA’s Goddard Space Flight Center. “Decisionmakers find this to be the most useful because it can be used to infer where there might be flooding when snow melts, and how much water can be expected to provide for irrigation during the growing season.”

The maps above show a difference from one year to the next, but how unusual was the snowfall? That depends on the river basin. The modeled data are used by the USGS Earth Resources Observation and Science Center to examine how snow water volume in 18 of Afghanistan’s river basins deviates from the previous year and from the 2001–2015 average. The time series shows that indeed, most basins were above average on February 6, 2017. An anomaly map shows the big-picture differences from the 2002-2014 average.

These data are also used by meteorologists at the NOAA Climate Prediction Center to summarize international weather and natural hazard conditions. The conditions are reported during a weekly webinar with people who study climate and its effect on agriculture (agroclimatologists) and with food security analysts with USAID’s Famine Early Warning Systems Network.

“The availability and access to food are both dimensions of food security,” McNally said. “Weather and water resource information from models and remote sensing can inform questions regarding water availability for crops; hazards like avalanches, or floods that may limit access to food.”

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El Niño: Pacific Wind and Current Changes Bring Warm, Wild Weather

El Niño is one of the most important weather-producing phenomena on Earth. The changing ocean conditions disrupt weather patterns and marine life in the Pacific and around the world. Satellites are unraveling the many traits of this wild child of weather.

This animation compares sea surface heights in the Pacific Ocean as measured by the altimeter on the OSTM/Jason-2 satellite and analyzed by scientists at NASA’s Jet Propulsion Laboratory. It shows sea surface height anomalies, or how much the water stood above or below its normal sea level. Shades of red indicate where the ocean was higher because warmer water expands to fill more volume (thermal expansion). Shades of blue show where sea level and temperatures were lower than average (water contraction). Normal sea-level conditions appear in white.

As you watch sea surface heights change through 2015, note the pulses of warmer water moving east across the ocean. When the trade winds ease and bursts of wind come out of the west, warm water from the western Pacific pulses east in vast, deep waves (Kelvin waves) that even out sea level a bit. As the warm water piles up in the east, it deepens the warm surface layer, lowering the thermocline and suppressing the natural upwelling that usually keeps waters cooler along the Pacific coasts of the Americas.

Read more about El Niño:

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Dek and Daga Islands, Ethiopia

An astronaut aboard the International Space Station took this photograph of Dek and Daga Islands in Lake Tana, Ethiopia. Both islands are volcanic in origin, as is the lake itself.

Situated in the Amhara Region of the Ethiopian Highlands, Lake Tana is the largest lake in Ethiopia and acts as the headwaters of the Blue Nile River. Dek Island—at 7 kilometers or 4.4 miles from north to south—is the largest island in Lake Tana. The murky green color of the water results from algal blooms, which that live on nutrients supplied from fertilizer fields, wastewater, and other sources of runoff that create nutrient pollution.

The dark green areas in the photo are patches of forest, while the lighter-toned and darker, salmon-colored patches are agricultural fields, which cover 70 percent of Dek Island. It is a prime area for farming because of high-quality volcanic soils, as well as heavy rains due to its location in the Intertropical Convergence Zone (ITCZ). Some of the more common crops are corn and millet, which are mostly consumed by the islanders. Coffee and mangos are the economic mainstays and are shipped to markets on the mainland.

Both islands are home to monasteries of the Coptic Church, most famously Narga Selassie on Dek Island and Daga Estefanos on Daga Island. For hundreds of years, the islands have helped protect the monasteries during times of war. Daga Estefanos is the resting place of mummified emperors who ruled Ethiopia (once known as Abyssinia) centuries ago.

This long-lens image illustrates the level of detail possible from a handheld digital camera shooting from the space station: the numerous white specks are the reflective tin roofs of houses and buildings.

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Cleaning Up Cookstoves

Nearly 3 billion people around the world use traditional cookstoves that burn charcoal, coal, wood, crop residue, or animal dung. Though such solid fuels are cheap and readily available, they emit harmful pollutants that liquid fuels—propane, butane, and kerosene—do not. For this reason, many government agencies, public health advocates, and environmental groups are racing to provide cleaner options in countries where traditional cookstoves are still common.

Such efforts may get a boost from a new study that suggests how to target clean cookstove programs most effectively. “Many programs simply target countries with large numbers of traditional cookstoves,” said University of Colorado researcher Forrest Lacey, the lead author of the study. “Our goal was to use quantitative tools and modeling to look carefully at the environmental conditions and meteorology around the world to better understand where reducing cookstove pollution would have the biggest impact on both human health and the climate.”

Lacey and colleagues developed a model that merged demographics and population data, emissions inventories, meteorological conditions, and satellite-based observations of haze. Their modeling effort looked at how reductions in cookstove pollution would evolve over the next hundred years.

They found that eliminating cookstove emissions over a 20-year period would prevent 10.5 million premature deaths and would help offset global warming slightly. However, they also found that targeting the countries with the most cookstoves and the most solid fuel burned was not always the most effective approach. In fact, when measured by benefits accrued per cookstove eliminated, changes in smaller countries had some outsized effects.

For instance, reducing pollution in Azerbaijan, Kazakhstan, Kyrgyzstan, Uzbekistan, and Ukraine would yield outsized climate benefits because winds often blow soot from these countries onto Arctic ice or snow-covered mountains, where the climate effects are amplified.

Likewise, while reducing cookstove pollution in large population countries such as China, India, and Bangladesh would prevent the most premature deaths, reducing cooking pollution in Nepal, Pakistan, and Vietnam would be particularly beneficial because wind patterns tend to transport air pollution over populated areas rather than to remote areas or out to sea.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP captured this natural-color image of haze over Bangladesh on January 28, 2017. Cookstoves are a significant contributor to poor air quality in Bangladesh, particularly in the winter when meteorological conditions tend to trap pollution near the surface.

“The bottom line is that clean cookstove efforts will save lives and protect the environment anywhere they are implemented,” said Lacey. “But my hope is that this study causes people to look more closely at some of the countries that may have been overlooked in the past when considering clean cookstove programs.”

Lacey and colleagues used a global transport model—which simulates how pollutants move and behave in the atmosphere—known as GEOS-Chem, which is driven by data from NASA’s Goddard Earth Observing System. The satellite observations come from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Image Spectroradiometer (MISR), sensors that monitor air quality by measuring airborne particles called aerosols. The research was funded in part by NASA’s Air Quality Applied Science Team. The photograph, taken by Joanna Pinneo, shows a woman using a traditional cookstove in Tanzania.

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February Puzzler

Our latest puzzler is out. Quick, what is this, where is it, and what makes this image interesting?


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The Zones of Kilimanjaro

Stories about Mount Kilimanjaro often focus on its height and location. The mountain—the tallest in Africa—is capped with snow and ice, despite sitting at a tropical latitude close to the equator. This volcanic mountain in Tanzania also has been in the news lately because that snowcap is shrinking, and scientists have gone to great lengths to understand why.

Viewed from a wide, top-down view, Kilimanjaro becomes compelling for a different reason: To get to the icy summit, you must pass through incredibly diverse vegetation zones. Those zones are visible in this natural-color image, acquired on January 20, 2017, by the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite. The mountain rises 5200 meters (17,000 feet) from the hot, dry savanna, through rainforest and hardy scrublands, to a rocky and icy summit at 5895 meters (19,340 feet) above sea level.

People have cultivated the lowlands ringing the mountain, which appear as patchy green areas in the bottom-left corner of this image. There is little natural vegetation on the foothills. Instead, people have taken advantage of the volcano’s rich soil to grow maize and beans, and to establish home gardens and coffee farms.

The continuous dark-green band around the mountain is forest, which stretches from roughly 1800 to 2800 meters in altitude. Ground-based researchers have found distinct ecosystems and forest types within this green band, but from space, we mostly see it as the lower boundary of Kilimanjaro National Park. When the park was established in 1973, only small corridors within the forest belt were protected. In 2005, the park boundaries were redrawn to include the more of the montane forests.

As we move up Kilimanjaro, the dark green areas transition to a band of green-brown known as the moorland zone. Vegetation still survives here, but it is nothing like the wet, humid forests found at lower elevations. The climate is colder and less humid, and the landscape is full of shorter, hardier plants such as the mountain’s iconic senecios and lobelias. The moorland landscape extends to about 4000 meters, above which vegetation becomes even more scarce.

The highest alpine desert and summit zones are relatively inhospitable. But climbers who make the journey are rewarded with an expansive view.

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Melbourne, Australia

Flying over southeastern Australia, an astronaut aboard the International Space Station took this photograph of the center of Melbourne. With a population of about 4.5 million people (as of 2015), greater Melbourne is the second-most populous city in Australia after Sydney.

The city straddles the Yarra River, which runs through the view as a darker line. Like most high-rise city centers, the center of Melbourne appears darker due to the long shadows cast by closely-spaced, tall buildings. The riverside sector is the tourist and conventioneer magnet; the Convention Center is one of the largest buildings in the neighborhood.

Angular patterns along the river (the Docklands) and the protected shoreline of Port Phillip Bay are transhipment facilities—interchanges between road, rail, and sea transportation. Melbourne is Australia’s busiest container port, with a well-developed railroad and freeway network to distribute goods, as shown by the tracks and highways immediately north of the Docklands.

Green patches in the image are parks, the largest being immediately east of the city center. The Sports and Entertainment Precinct occupies one of these open spaces. It is home to the largest (circular) stadium in the southern hemisphere, the iconic Melbourne Cricket Ground (founded in 1853). On the opposite bank of the Yarra River lies the state governor’s mansion known as the Government House. A smaller park hosts the Royal Exhibition Building, the venue of the first Parliament of Australia. With a design based partly on Florence Cathedral, the building was the first non-Aboriginal cultural site in Australia to win UNESCO’s World Heritage listing.

Various place names reflect the time when Melbourne was founded. At its founding in 1835, the city was named in honor of the British Prime Minister (William Lamb, 2nd Viscount Melbourne). In 1851, it became the capital of the newly founded colony of Victoria, named for the British Queen. Roads and parks are also named after Queen Victoria’s husband Prince Albert.

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Satellites Capture Different Views of Devastating Fires in Chile

Wildfires continued to ravage Chile’s countryside in early February 2017, weeks after they flared up in mid-January. The blazes have thwarted firefighters’ efforts to control them, with new hot spots emerging daily. Satellite data and scientific analysis suggest the fires are among the worst the country has seen in decades.

Since the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite began collecting data in 2002, fires have occurred in a fairly steady, cyclical pattern in Chile, rising during the dry season and falling during wetter months. Between 2003 and 2016, MODIS detected an average of 330 daytime fire hot spots throughout Chile during the month of January. In 2017, the number jumped tenfold.

“This is unprecedented from my perspective. The smoke plumes are huge in abundance and altitude,” said Michael Fromm, a meteorologist with the Naval Research Laboratory who has been studying satellite fire data for 15 years. “Fires have gotten much larger and much more energetic than typical for that area.”

The fires left a massive burn scar near Empedrado, Chile. On January 24, 2017, the Operational Land Imager (OLI) on the Landsat 8 satellite acquired a false-color image (first image) of scorched land flanked by actively burning fires. The image combines shortwave infrared, near-infrared, and green light (OLI bands 7-5-3) to distinguish burned area (brown) from unscarred land (green).

Smoke from the fires has been traveling hundreds to thousands of kilometers, satellite data shows. According to Santiago Gassó, an aerosol scientist at NASA’s Goddard Space Flight Center, the smoke has reached areas in the Central South Pacific, which is unusual.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured natural-color images of the smoke on January 27 and 28 as it blew over central Chile and the Pacific Ocean. Smoke has a blue or brown tint compared to white clouds. The horizontal red line on each image shows the orbital track taken by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), which collected data through a vertical slice of the atmosphere.

The CALIPSO profiles above show the altitude of clouds and smoke plumes. Close to the active fires, smoke rose 2 to 3 kilometers (1 to 2 miles) high, sufficient to be visible above low-altitude clouds. As it traveled downwind and over the open ocean, smoke rose to altitudes as high as 8 kilometers (5 miles).

As of late January, the fires had consumed roughly 273,000 hectares (1,060 square miles), burned several villages to the ground, and killed at least 11 people, according to news reports. The burned area continues to grow, and multiple towns remain on red alert. Other countries, as well as non-profit organizations and individuals, have donated funds to relief and fire-fighting efforts.

There were 123 active forest fires registered in Chile on February 2, 2017, according to an update by the National Forest Corporation (CONAF). Firefighters were actively fighting 51 blazes; 68 had been controlled and 12 had been extinguished.
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