Tag: Earth’s Surface and Interior

Earth’s Surface and Interior

NASA Earth Observatory image (top) by Joshua Stevens using Landsat data from the U.S. Geological Survey and ASTER GDEM2 data from NASA/MITI and the ASTER Science Team.

NASA Earth Observatory image (top) by Joshua Stevens using Landsat data from the U.S. Geological Survey and ASTER GDEM2 data from NASA/MITI and the ASTER Science Team.

At approximately 6:45 a.m. on April 18, 2014, a block of ice tumbled from the edge of a hanging glacier onto a popular climbing route on the south face of Mount Everest. The ice, which weighed as much as 657 passenger buses, tumbled about 400 meters (1,300 feet) and triggered an avalanche. The falling ice and rock overwhelmed a group of Nepalese guides who were ferrying equipment from Base Camp (elevation 5,270 meters) to Camp 1 (elevation 6,035 meters) for foreign clients. Sixteen guides died in the avalanche, making it Everest’s deadliest day.

This three-dimensional rendering—made with data collected by the Operational Land Imager on Landsat 8 and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on Terra—offers a broad view of the topography that climbers face. Read More

ASTER GED with Death Valley

 

ASTER GED Death Valley Color Bar

Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

Like the sun, Earth emits energy, yet this energy cannot be seen. Instead, it can be felt as heat because it is emitted in the thermal infrared wavelength range of the electromagnetic spectrum. While some energy in the electromagnetic spectrum can be seen in the form of light, other energy can only be felt as heat. For example, if you stand next to an oven or hover your hand over a hot burner you can feel the heat being emitted without directly touching either appliance. The strength of the energy emitted depends on both the temperature of the surface and how efficiently it can emit radiation, known as its emissivity.

The emissivity of most natural Earth surfaces is a unitless quantity and ranges between approximately 0.6 and 1.0, but surfaces with emissivities less than 0.85 are typically restricted to deserts and semi-arid areas. Vegetation, water and ice have high emissivities, above 0.95 in the thermal infrared wavelength range.

Instruments sensitive to thermal infrared radiation on-board NASA’s Earth Observing Satellites are designed to calculate Earth’s emissivity. The Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on-board Terra is one of these instruments. It calculates emissivity at 90 m spatial resolution for five different wavelengths in the thermal infrared spectrum. Scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California produced the most detailed global map of emissivity by compositing millions of clear-sky images from ASTER, collected since its launch in 2000. This global map is the ASTER Global Emissivity Database (ASTER GED). ASTER GED is approximately 100 times more detailed than any other previous emissivity map produced by NASA.

Emissivity, unlike surface temperature, is an intrinsic property of the surface and does not depend on the angle of the sun in relationship to Earth or on local weather conditions. Instead emissivity variations occur due to land cover and use changes, as well as, the mineral composition of the land’s surface.

In the image, red areas (>0.95) have high emissivity and are covered with large amounts of vegetation, water, or ice. Blue areas (<0.8) have low emissivity and are indicative of quartz sands, which are found in arid regions such as the Sahara Desert in northern Africa. Transition areas from desert regions to more heavily vegetated regions, such as in the Sahel in Africa, appear green and yellow.

ASTER GED is a global, 90m spatial resolution emissivity map of the Earth’s non-frozen land surfaces at five different wavelengths in the thermal infrared spectrum. ASTER along with the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board both Terra and Aqua and the Atmospheric Infrared Sounder (AIRS) on-board Aqua measure thermal infrared radiation. Therefore, the high resolution ASTER GED can be used to calibrate and validate these instruments coarser resolution estimates of emissivity at the kilometer-scale. ASTER GED is also being used for improving estimates of Earth’s surface temperature, atmospheric water vapor, and the accuracy of climate models, which currently have large uncertainties in their use of emissivity information.

Resources:

Jet Propulsion Laboratory Photojournal. (2014, October 20). NASA Spacecraft Maps Earth’s Global Emissivity. accessed October 23, 2014.

Land Processes Distributed Active Archive Center. (2014, April 2). ASTER Global Emissivity Database (GED) Product Release. Accessed October 7, 2014.

Joint Emissivity Database Initative (JEDI) Accessed October 7, 2014

ASTER-GED. Accessed October 23, 2014

aralsea_tmo_2014231

NASA Earth Observatory image by Jesse Allen, using data from the Level 1 and Atmospheres Active Distribution System (LAADS). Caption by Kathryn Hansen.

Summer 2014 marked another milestone for the Aral Sea, the once-extensive lake in Central Asia that has been shrinking markedly since the 1960s. For the first time in modern history, the eastern basin of the South Aral Sea has completely dried.

This image pair from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite shows the sea without its eastern lobe on August 19, 2014. Read more

sulaiman_ast_2011114_imbricate

While not as high as the Himalayas or Karakoram, the Sulaiman range boast some of the most complex tectonic structures in the world. As India moved northward, it began to rotate in a counter-clockwise direction, wrenching the northwestern part of the Indian plate backwards into part of the Eurasian plate. The countervailing forces put the rocks of the Sulaiman range in a unique compressional vice, causing many of its faults to curve and stretch in convoluted ways.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA’s Terra satellite captured a scene on April 24, 2011, that highlights some of this tectonic complexity. Read more

NASA Earth Observatory image by Robert Simmon and Adam Voiland, with data courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team. Caption by Adam Voiland.

indonesia_tmo_2014151

Due to elevated seismic activity, the Volcanological Survey of Indonesia issued an alert for Sangeang Api—an island volcano in the Flores Sea—on May 21, 2014. Sangeang erupted explosively on May 30, sending a thick column of ash and sulfur dioxide billowing into the atmosphere.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite captured imagery of the eruption plume the next day. Terra acquired this image at 2:35 UTC (10:35 a.m. local time) on May 31, 2014. Ash drifted southeast, shutting down airports in Bima, Indonesia, and Darwin, Australia. Service to Darwin resumed by June 1, but Bima remained shut down as of June 2, according to the Jakarta Globe. Read more

NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Caption by Adam Voiland.