# Presentation: 696034

## Drought and Burn Scars in Southeastern Australia

**14 February 2002 and 17 February 2003**

**Notes:**
More than 2 million acres were consumed by hundreds of fires between December 2002 and February 2003 in southeastern Australia's national parks, forests, foothills and city suburbs. These images were acquired on February 14, 2002 (left) and February 17, 2003 (right) by the Multi-angle Imaging SpectroRadiometer (MISR) instrument onboard NASA's Terra satellite. The year 2002 was one of Australia's hottest and driest on record, and the acreage burnt during the summer 2002-2003 fire season in Victoria, the Australian Capital Territory and southern New South Wales, is the largest since 1938-1939, when more than 3 million acres were scorched.

The extent of the burnt area and the dry conditions as of February 2003 are indicated by these contrasting false-color views. Both image panels display data from the near-infrared, red and blue spectral bands of MISR's downward-viewing (nadir) camera, as red, green and blue, respectively. This display technique causes healthy vegetation to appear red and burnt areas to show as dark brown. The data displayed from the two dates were processed identically to preserve relative brightness variations. Vegetation changes related to the dry conditions (not related to the brown burn scars) are also indicated in the February 2003 panel, where many previously red areas exhibit instead the pale yellow-brown of the underlying soils and geology. Significant reduction in the surface area of several large and important water bodies are also apparent. The diminished extent of Lake Hume (along the left-hand edge) in the later date provides a good example.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbits 14999 and 16858. The panels cover an area of about 208 kilometers x 286 kilometers, and utilize data from blocks 118 to 121 within World Reference System-2 path 91.

Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).

## Smoke over Nigeria and the Gulf of Guinea

**31 January 2003**

**Notes:**
These images and data products from the Multi-angle Imaging SpectroRadiometer (MISR) document extensive smoke from fires burning throughout Nigeria and north central Africa on January 31, 2003. At left are natural-color views acquired by MISR's vertical-viewing (nadir) and most oblique forward viewing cameras. The images extend from arid Niger in the north (including the dark-colored Aïr Mountains), through forested Nigeria, and beyond the Niger Delta to the Gulf of Guinea and the open ocean. Smoke present in the lower portion of the images, and a series of thin, high clouds, are more apparent at the oblique view angle. Although numerous small smoke plumes emanate from fires buring within the image area, some of the smoke can also be attributed to fires that were burning across the north central African Sahel and savanna regions at this time and during the previous two weeks.

A map of aerosol optical depth, which is a measure of atmospheric particle abundance, is shown at center-right. MISR utilizes the changes in the atmosphere's ability to transmit light and the variation in scene brightness at different view angles to retrieve aerosol optical depth and deduce some of the properties of the particles. A thick pall of smoke is present over Nigeria and the Gulf of Guinea, indicated by green, yellow and red pixels over these regions. Clear skies are indicated by the blue and purple pixels over the desert regions and ocean. Places where clouds or other factors precluded an aerosol retrieval are shown in dark gray.

The position of clouds appears to move with view angle relative to the ground due to geometric parallax. MISR utilizes the parallax effect to generate its stereo height fields. The right-hand panel is a stereoscopically derived cloud mask (SDCM), which classifies regions as clear or cloudy based upon their heights above the surface and is one of several cloud masks produced by MISR. The high and low confidence designations are related to how well the stereo height retrieval algorithms were able to determine the absolute height of the clouds. The pall of smoke, unlike the clouds and underlying surface, does not contain an organized spatial texture, and the stereo retrievals classify the smoke-filled regions as clear despite the large abundance of airborne particles.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 16602. The panels cover an area of about 380 kilometers x 2520 kilometers, and utilize data from blocks 74 to 92 within World Reference System-2 path 189.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).

## Lutzow-Holm Bay and the Shirase Glacier, Antarctica

**5 September 2002**

**Notes:**
These views from the Multi-angle Imaging SpectroRadiometer (MISR) portray the Lutzow-Holm Bay region of Queen Maud Land, East Antarctica, on September 5, 2002. Although Queen Maud Land remains one of the least studied regions of Antarctica, Lutzow-Holm Bay is an exception. Syowa (pronounced 'Showa') Station is the Japanese Antarctic Research Expedition base situated on Ongul Island, just off the eastern coast of the Bay (in the top right-hand portion of these views). Scientists there have studied changes in the ice sheet and sea level for several decades. Large outlet glaciers, such as the fast-flowing Shirase Glacier in the lower right-hand corner of these images, are the primary drainage systems for the Antarctic ice sheet.

These two views provide information on both the spectral and angular reflectance properties of the region and can be used to understand the geophysical environment. The top panel shows the region from MISR's downward-looking (nadir) camera and is a false-color view in which the near-infrared, green and blue spectral bands have been displayed as red, green and blue. Because of the tendency of water to absorb near-infrared wavelengths, some ice types exhibit an especially bright blue hue in this display.

The lower panel is a multi-angular composite from three MISR cameras in which changes in reflection at different view angles, as well as in the near-infrared spectral region, assist with the identification of rough and smooth ice surfaces. In this display, red band data from MISR's 60-degree forward and backward-viewing cameras are displayed as red and blue, respectively, and near-infrared data from the nadir camera are displayed as green. Using this technique, surfaces that predominantly exhibit backward scattering (generally rough surfaces) appear red/orange, and surfaces that predominantly exhibit forward scattering (generally smooth surfaces) appear in blue hues. Clouds (and other surfaces that exhibit both forward and backward scattering) appear purple.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 16454. The panels cover an area of about 335 kilometers x 257 kilometers, and utilize data from blocks 145 to 147 within World Reference System-2 path 151.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).

## Seasonal Surface Changes in Namibia and Central Angola

**6 March 2001 (top) and 1 September 2002 (bottom)**

**Notes:**
Brightness variations in the terrain along a portion of southwestern Africa are displayed in these views from the Multi-angle Imaging SpectroRadiometer (MISR). The panels portray an area that includes Namibia's Skeleton Coast and Etosha National Park as well as Angola's Cuando Cubango. The top panels were acquired on March 6, 2001, during the region's wet season, and the bottom panels were acquired on September 1, 2002, during the dry season. Corresponding changes in the abundance of vegetation are apparent. The images on the left are natural color (red, green, blue) images from MISR's vertical-viewing (nadir) camera. The images on the right represent one of MISR's derived surface products.
The radiance (light intensity) in each pixel of the so-called "top-of-atmosphere" images on the left includes light that is reflected by the Earth's surface in addition to light that is transmitted and reflected by the atmosphere. The amount of radiation reflected by the surface into all upward directions, as opposed to any single direction, is important when studying Earth's energy budget. A quantity called the surface "directional hemispherical reflectance" (DHR), sometimes called the "black-sky albedo", captures this information, and is depicted in the images on the right. MISR's multi-angle views lead to more accurate estimates of the amount of radiation reflected into all directions than can be obtained as a result of looking at a single (e.g., vertically downward) view angle. Furthermore, to generate this surface product accurately, it is necessary to compensate for the effects of the intervening atmosphere, and MISR provides the ability to characterize and account for scattering of light by airborne particulates (aerosols).
The DHR is called a hemispherical reflectance because it measures the amount of radiation reflected into all upward directions, and which therefore traverses an imaginary hemisphere situated above each surface point. The "directional" part of the name describes the illumination geometry, and indicates that in the absence of an intervening atmosphere, light from the Sun illuminates the surface from a single direction (that is, there is no diffuse skylight, hence the "black-sky" terminology). The DHR is retrieved over land surfaces in each of MISR's four wavelength bands, and the images on the right are red, green, blue spectral composites. Regions where DHR could not be derived, either due to an inability to retrieve the necessary atmospheric characteristics or due to the presence of clouds, are shown in dark gray.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbits 6466 and 14388. The panels cover an area of about 380 kilometers x 760 kilometers, and utilize data from blocks 102 to 107 within World Reference System-2 path 181.

Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory) and David J. Diner (Jet Propulsion Laboratory).

## Casting Light and Shadows on a Saharan Dust Storm

** ****3 March 2003**

**Notes:**
On March 2, 2003, near-surface winds carried a large amount of Saharan dust aloft and transported the material westward over the Atlantic Ocean. These observations from the Multi-angle Imaging SpectroRadiometer (MISR) aboard NASA's Terra satellite depict an area near the Cape Verde Islands (situated about 700 kilometers off of Africa's western coast) and provide images of the dust plume along with measurements of its height and motion. Tracking the three-dimensional extent and motion of airmasses containing dust or other types of aerosols provides data that can be used to verify and improve computer simulations of particulate transport over large distances, with application to enhancing our understanding of the effects of such particles on meteorology, ocean biological productivity, and human health.
MISR images the Earth by measuring the spatial patterns of reflected sunlight. In the upper panel of the still image pair, the observations are displayed as a natural-color snapshot from MISR's vertical-viewing (nadir) camera. High-altitude cirrus clouds cast shadows on the underlying ocean and dust layer, which are visible in shades of blue and tan, respectively. In the lower panel, heights derived from automated stereoscopic processing of MISR's multi-angle imagery show the cirrus clouds (yellow areas) to be situated about 12 kilometers above sea level. The distinctive spatial patterns of these clouds provide the necessary contrast to enable automated feature matching between images acquired at different view angles. For most of the dust layer, which is spatially much more homogeneous, the stereoscopic approach was unable to retrieve elevation data. However, the edges of shadows cast by the cirrus clouds onto the dust (indicated by blue and cyan pixels) provide sufficient spatial contrast for a retrieval of the dust layer's height, and indicate that the top of layer is only about 2.5 kilometers above sea level.
Motion of the dust and clouds is directly observable with the assistance of the multi-angle "fly-over" animation. The frames of the animation consist of data acquired by the 70-degree, 60-degree, 46-degree and 26-degree forward-viewing cameras in sequence, followed by the images from the nadir camera and each of the four backward-viewing cameras, ending with 70-degree backward image. Much of the south-to-north shift in the position of the clouds is due to geometric parallax between the nine view angles (rather than true motion), whereas the west-to-east motion is due to actual motion of the clouds over the seven minutes during which all nine cameras observed the scene. MISR's automated data processing retrieved a primarily westerly (eastward) motion of these clouds with speeds of 30-40 meters per second. Note that there is much less geometric parallax for the cloud shadows owing to the relatively low altitude of the dust layer upon which the shadows are cast (the amount of parallax is proportional to elevation and a feature at the surface would have no geometric parallax at all); however, the westerly motion of the shadows matches the actual motion of the clouds. The automated processing was not able to resolve a velocity for the dust plume, but by manually tracking dust features within the plume images that comprise the animation sequence we can derive an easterly (westward) speed of about 16 meters per second. These analyses and visualizations of the MISR data demonstrate that not only are the cirrus clouds and dust separated significantly in elevation, but they exist in completely different wind regimes, with the clouds moving toward the east and the dust moving toward the west.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 17040. The panels cover an area of about 312 kilometers x 242 kilometers, and use data from blocks 74 to 77 within World Reference System-2 path 207.

Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
Text acknowledgment: Clare Averill (Acro Service Corporation/Jet Propulsion Laboratory).

## Where on Earth...? MISR Mystery Image Quiz #13

**26 June 2002**

## Windswept Shores of the Aral Sea

**3 December 2002**