New Views of the Earth at Night

Out of the Blue and Into the Black

New Views of the Earth at Night

The night is nowhere near as dark as most of us think. In fact, the Earth is never really dark. And we don’t have to be in the dark about what is happening at night anymore either. —Steven Miller, atmospheric scientist, Colorado State University

By Michael CarlowiczDesign by Paul PrzyborskiDecember 5, 2012

The night side of Earth twinkles with light. The first thing to stand out is the cities. “Nothing tells us more about the spread of humans across the Earth than city lights,” asserts Chris Elvidge, a NOAA scientist who has studied them for 2

Away from human settlements, light still shines. Wildfires and volcanoes rage. Oil and gas wells burn like candles. Auroras dance across the polar skies. Moonlight and starlight reflect off the water, snow, clouds, and deserts. Even the air and ocean sometimes glow.

A handful of scientists have observed earthly night lights over the past four decades with military satellites and astronaut photography. But in 2012, the view became significantly clearer. The Suomi National Polar-orbiting Partnership(NPP) satellite — launched in October 2011 by NASA, the National Oceanic and Atmospheric Administration (NOAA), and the Department of Defense — carries a low-light sensor that can distinguish night lights with six times better spatial resolution and 250 times better resolution of lighting levels (dynamic range) than before. Also, because Suomi NPP is a civilian science satellite, data is available to scientists within minutes to hours of acquisition.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP can observe dim light down to the scale of an isolated highway lamp or fishing boat. It can even detect faint, nocturnal atmospheric light — known as airglow — and observe clouds lit by it. Through the use of its “day-night band,” VIIRS can make the first quantitative measurements of light emissions and reflections, distinguishing the intensity and the sources of night light. The sum of these measurements gives us a global view of the human footprint on the Earth.

“These lights have always been there, but we’ve never had an ability to take full advantage of them,” Miller says. “Now we finally have a way of doing that.”

“City lights provide a fairly straightforward means to map urban versus rural areas, and to show where major population centers are and where they are not,” says William Stefanov of the International Space Station program. (View Large Image - NASA Earth Observatory and NOAA National Geophysical Data Center)

Light from the aurora australis,or “southern lights,” is bright enough to reveal the ice edge in Antarctica’s Queen Maud Land. (View Large Image - NASA Earth Observatory and NOAA National Geophysical Data Center)

Moon Phases Over the Persian Gulf

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured these nighttime views of the Persian Gulf region on September 30, October 5, October 10, and October 15, 2012. The images are from the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as gas flares, auroras, wildfires, city lights, and reflected moonlight.

Each image includes an inset of the Moon in four different phases. September 30 shows the Persian Gulf by the light of the full Moon; October 15 shows the effects of a new Moon. As the amount of moonlight decreases, some land surface features become harder to detect, but the lights from cities and ships become more obvious. Urbanization is most apparent along the northeastern coast of Saudi Arabia, in Qatar, and in the United Arab Emirates (UAE). In Qatar and UAE, major highways can even be discerned by nighttime lights.

In eighteenth-century England, a small group of entrepreneurs, inventors and free thinkers—James Watt and Charles Darwin’s grandfathers among them—started a club. They named it the Lunar Society, and the “lunaticks” scheduled their dinner meetings on evenings of the full Moon. The timing wasn’t based on any kind of superstition, it was based on practicality. In the days before electricity, seeing one’s way home after dark was far easier by the light of a full Moon. In the early twenty-first century, electricity has banished the need for such careful scheduling, but the light of the full Moon still makes a difference.

1.  References

2.   Uglow, J. (2002) The Lunar Men: Five Friends Whose Curiosity Changed the World. New York: Farrar, Straus and Giroux.

NASA Earth Observatory image by Jesse Allen and Robert Simmon, using VIIRS day-night band data from the Suomi National Polar-orbiting Partnership. Suomi NPP is the result of a partnership between NASA, the National Oceanic and Atmospheric Administration, and the Department of Defense. Caption by Michon Scott.

Instrument: 

Suomi NPP - VIIRS

BLUE MARBLE

Dust Plumes over the Arabian Sea گرد و غبار، دود و مه

 گرد و غبار سواحل ایران و پاکستان در اواخر ماه نوامبر 2012. 

Multiple dust plumes blew off the coasts of Iran and Pakistan on November 29, 2012. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite observed the dust plumes in the morning, and MODIS on the Aqua satellite observed the plumes in the afternoon.

These images document the movement of the plumes southward over the Arabian Sea. The plumes apparently arose from fine sediments near the coast. Some of the plumes were thick enough to hide the water surface below, especially two large plumes off the coast of Pakistan. On the afternoon of November 29, those plumes fanned out over the ocean water.

Sand seas, saltpans, and impermanent rivers in this region provide sediments that can easily be lofted into the air. The southern coasts of Pakistan and Iran rank among the world’s leading dust-producing regions.

1.  References

2.   University Corporation for Atmospheric Research. Forecasting Dust Storms. (Registration required).

NASA images courtesy Jeff Schmaltz, LANCE MODIS Rapid Response. Caption by Michon Scott.

Instrument: 

The catastrophic mudslides

Around midnight on Aug. 8, 2010, a violent surge of loosened earth roared down mountain slopes and slammed into quietly sleeping neighborhoods in Zhouqu County in Gansu, China. The catastrophic mudslides -- the deadliest in decades according to state media -- buried some areas under as much as 23 feet (7 meters) of suffocating sludge. 1,765 people died. Property damages totaled an estimated $759 million. Cutting from right to left, this detailed image, from DigitalGlobe’s WorldView-2 satellite, shows the largest slide in the lower part of the city on Aug. 10, 2010.
Credit: Image from WorldView-2 © 2010 by DigitalGlobe

A NASA study using TRMM satellite data revealed that the year 2010 was a particularly bad year for landslides around the world.

A recent NASA study published in the October issue of the Journal of Hydrometeorology compared satellite rain data from NASA’s Tropical Rainfall Measurement Mission (TRMM) to landslides in central eastern China, Central America and the Himalayan Arc, three regions with diverse climates and topography where rainfall-triggered landslides are frequent and destructive hazards to the local populations.

The work, led by Dalia Kirschbaum, a research physical scientist in the Hydrological Sciences Laboratory at NASA's Goddard Space Flight Center in Greenbelt, Md., is part of an ongoing effort to catalog worldwide rainfall-triggered landslides—one of the world's lesser known but often catastrophic natural hazards. Locating them is a step in an effort to be able, one day, to predict and warn.

Currently, Kirschbaum explains, no consistent regional or global scale warning system exists for landslide disasters. To create one, scientists need to understand more than the individual factors that may contribute to local landslides -- the intensity and total amount of rainfall over hours to days, slope angle, soil type and saturation, among others.

"For other hazards like hurricanes, there's a clearly defined season," says Kirschbaum. "From satellite data and observations we know that hurricane season in the Atlantic spans from June 1 to Nov. 30. But we don't have that type of record for landslides around the world, and we want to know when and where to expect them in different regions."

Scientists also need a systematic way to assess landslide hazards for a region, and one way to do that, says Kirschbaum, is to look at the distribution and intensity of rain from satellite data and see how that correlates with where and how often landslides are being reported.

Mergui Archipelago

In the southernmost reaches of Burma (Myanmar), along the border with Thailand, lies the Mergui Archipelago. The archipelago in the Andaman Sea is made up of more than 800 islands surrounded by extensive coral reefs.

This natural color image acquired by Landsat 5 on Dec. 14, 2004, shows the middle portion of the archipelago, including Auckland and Whale Bays. Swirling patterns are visible in the near-shore waters as sediments carried by rivers slowly settle out and are deposited on the seafloor. The heavy sediment loads make the river appear nearly white. As those sediments settle out, the seawater appears deeper shades of blue. The tropical rainforests of the region appear deep green.

Captain Thomas Forrest of the East India Company first described the region to Europeans after a 1782 expedition in search of potential sugar-growing lands. At that time, the islands were mainly inhabited by a nomadic fishing culture. These people, known as the Moken, still call the archipelago home and mostly live a hunter-gatherer lifestyle. As of 2006, 2,000 Moken were known to inhabit the Burmese portion of Mergui.

The small population of the archipelago has helped preserve its high diversity of plants and animals. In 1997, Burma opened the region to foreign tourism and in the years since it has become a major diving destination. A valued species of pearl oyster (Pinctada maxima) are found in nearby waters. Today, overfishing is emerging as a regional problem.

1.  References

2.   Alagarswami, K. (1983). The Black-Lip Pearl Oyster Resource and Pearl Culture Potential. CMFRI Bulletin, 34: Mariculture Potential, pp. 72–78.

3.   Anderson, John (1890). The Selungs of the Mergui Archipelago. Trübner & Co., Ludgate Hill, London. (http://hdl.handle.net/2027/mdp.39015058537070)

4.   Arunotai, Narumon (2006). Moken traditional knowledge: an unrecognized form of natural resources management and conservation. UNESCO. Blackwell Publishing Ltd., Oxford, UK.

5.   Brown, R.N.R. (1907). The Mergui Archipelago: Its People and Products. Scottish Geographical Magazine, vol. 23, issue 9, pp. 463–483. (http://www.tandfonline.com/doi/abs/10.1080/00369220708733785)

6.   Wikipedia (2012). Mergui Archipelago. Accessed 23 Nov. 2012.

Landsat image created by Michael Taylor, Landsat Project Science Office. Caption by Laura Rocchio.