Studies of atmospheric aerosols, especially of anthropogenic pollution and dust, are critical for defining parameters in global change models. Photographs taken from low Earth orbit provide additional information to supplement data from ground stations and high-altitude satellite sensors. We use a haze event in the eastern USA as a case study to show the value of the photographs from low Earth orbit when integrated with point data acquired from ground stations. Five examples of probable anthropogenic hazes, some with associated ground data, from northern Italy, the Ukraine, and the Red Basin in China, the Nile River delta and southern Africa show the value of oblique and wide-angle views for capturing aerosol events on film. Through these examples we illustrate the large areas blanketed by haze masses, the high albedo of thick anthropogenic haze, and the well-known topographic control of haze distribution. Four examples from three continents illustrate regional (Tibetan Plateau, Andes Mts.) and intercontinental (Sahara-Europe, China-North America) movement of dust particles in major aerosol events.
Wilkinson, M. J., J. D. Wheeler, R. J. Charlson, and K. P. Lulla, 2000. Imaging aerosols from low Earth orbit: Photographic results from the Shuttle-Mir and Shuttle programs, in Dynamic Earth Environments: Remote Sensing Observations from Shuttle-Mir Missions (K. P. Lulla and L. V. Dessinov, eds.), John Wiley & Sons, New York, pp. 77-98, 263-265, 274-277.
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Figure 6.1
Climatic forcing by human activity - July 1993. Models suggest that net cooling may result over the major industrial regions of the world - eastern North America, western Europe, and east Asia - as a result of the reflective effect of anthropogenic haze in the atmosphere (-1 W per swaure meter and more in the centers of areas A, B, and C). Smoke from biomass burning explains the major southern hemisphere cooling center in Angola (D). Models further suggest an extensive zone a warming south of the equator (shaded box, +1 W per square meter over the oceanic sectors). Cooling in the centers of regions A, B, and C, with warming in much of the shaded box increases temperature gradients (adapted from Kiehl and Briegleb, 1993, and Charlson and Wigley, 1994). |
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Figure 6.2
Global distribution of major deserts and surrounding semiarid regions, with some common dust transport trajectories. (Data from Coude-Gaussen, 1984; Meigs, 1953; Wilkinson et al., 1998; F. Eckardt, R. WAshington, M. J. Wilkinson, and K. P. Lulla, unpublished data.) |
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Figure 6.3
This Space Shuttle photograph shows a major haze event in the eastern United States on April 26, 1990 (14:49:03 GMT). The view looks obliquely north along the east coast from a point above the Caribbean Sea. A mass of aerosol haze stretches across the top of the entire view. This mass was transported west to east (left to right in this view) around the north limb of the high pressure cell. It moved offshore for at least 1500 km, beyond the Atlantic islands of Bermuda (B). The leading edge of the haze mass can be detected (right center) north of the Bahamas (islands surrounded by light-blue seabed, bottom right), indicating that aerosols from the industrial Northeast were transported around the high, with a final trajectory leading directly toward the large population centers of Florida. (NASA photograph STS031-151-155, center point 26°N 80°W, craft nadir 20.9°N 83.4°W, Linhof camera, 90 mm lens, altitude 617 km.) |
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Figure 6.4
Meteorological conditions accompanying the haze shown in Figure 6.3 (color insert). (A) Barometric pressure at 12:00 GMT, April 26, 1990 (millibars). This pattern typifies the common summer pressure distribution known as the Bermuda High, with winds blowing clockwise around the center (H). Such a pattern would facilitate accumulation of atmospheric pollutants. AHN, Athens, Georgia; BNA, Nashville, Tennessee; CKL Centreville, Alabama; DAY, Dayton, Ohio; GSO, Greensboro, North Carolina; HTS, Huntington, West Virginia; JAN, Jackson, Mississippi; PAH, Paducah, Kentucky; PIT Pittsburgh, Pennsylvania (i>B) Surface relative humidity at 12:00 GMT on April 26, 1990. Although relative humidity is comparatively high throughout the eastern United States, fog development was possible only in the southernmost parts, excluding the possibility that aaerosols in Figuer 6.3 were due to fog. (From the National Climatic Data Center, 1998b.) |
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Figure 6.5
Vertical soundings of temperature (T, °C) and dew point (T, °C) versus altitude (mb) at 12:00 GMT on April 26, 1990 for six of the nine ground stations shown on Figure 6.4A. All soundings show TD< T such that relative humidity is less than 100% except in the extreme south, where humidity approaches 100% near the ground at Centreville, Alabama (CKL) and Jackson, Missouri (not shown). See city abbreviations in legend to Figure 6.4A. (From the National Climatic Data Center, 1998b.) |
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Figure 6.6
Visibility measurements show that the entire eastern third of the United States is under the influence of a widespread aerosol on April 26, 1990. Visibility is usually dominated by scattering of light and is estimated from visual range at numerous airports, shown here as daytime averages. Larger circles represent lower visibility (visibility is represented by the extinction coefficient, σ, which is proportional to the inverse visual range, in units of km-1). (from the National Climatic Data Center, 1998b.) |
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Figure 6.7
Sulfate content of atmospheric aerosol at Bermuda for March 1 to June 1,1990. Note that even higher loadings were measured at Bermuda on three other occasions within the few weeks before and after the event described here. (Data from J. Prospero, University of Miami, Miami, Florida, 1999, personal communication.) |
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Figure 6.8
Industrial haze flowing from the Po River Valley over the Adriatic Sea. Two panoramic views to the south-southwest, taken on successive days, show the Adriatic Sea (center left) and all of the peninsula of Italy (about 1000 km long), looking south from a point over the Alps whose rugged mountainous landscape appears in the foreground of view (A). The north end of the Adriatic Sea is partly obscured by industrial haze from the Po River valley (A, center and center right; B, foreground). The polluted air contrasts with the clearer air over the Adriatic further south (middle ground)-and also contrasts with patches of cloud and snow on the Alps, both of which are brilliant white and well delineated. Arrows in view (A) indicate the north-south line separating denser from less dense industrial aerosols on October 25, 1997 (11:58:07 GMT); the next day (October 26, 1997, 10:59:51 GMT) this line had swung around to an east-west position (arrows, B) as the haze drifted slowly south down the channel of the Adriatic Sea. [NASA photographs, Hasselblad camera, 100 mm lens, altitude 383 km: (A) NASA6-704-83, center point 43.5°N 13°E, craft nadir 50.6°N 10.6°E; (B) NASA6-707-65, center point 42.5°N 15°E, craft nadir 48.9°N 10.7°E.) |
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Figure 6.9
Numerous tendrils of polluted air (foreground) move southeast (from the lower right), from the western Ukraine toward Romania, maintaining their coherence for tens of kilometers on October 19, 1997 (13:02:42 GMT). Anthropogenic haze (H) also occupies the lower Danube basin in southern Romania, a topographic basin in which the Ukrainian haze appears to be accumulating. The Carpathian Mountains (C-C) appear with greater clarity above the inversion layer (below which lies the polluted air). The sun is reflected off rivers, revealing details of the Dniester River meanders (D-D) which represents a distance of ~280 km. The distance from the Dniester the Danube River at the arrows is ~600 km (arrows indicate the bend of the river at the Iron Gate on the Yugoslav border). (NASA photograph NASA6-703-50, center point 48.5°N 25.5°E, craft nadir 51.2°N 34.7°E, Hasselblad camera, 100 mm lens, altitude 383 km. |
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Figure 6.10
Anthropogenic Haze from China over the Pacific Ocean, early March, 1996. (A) The entire Red Basin of Sichuan Province filled with gray anthropogenic haze on a winter day as anticyclonic conditions were developing. In this west-looking view, the Tibetan Plateau stretches across the top of the view, and the snowcapped Himalaya Mountains appear in the extreme top left corner. The distance across the Red Basin is approximately 450 km; the horizontal distance from the Space Shuttle nadir to the basin margin is also about 450 km. (B) A coherent corridor of anthropogenic haze (arrows, probably a mixture of industrial air pollution, dust, and smoke) can be seen in the left half of the view against the dark background of the East China Sea. The corridor is about 200 km wide and probably much longer than 600 km (visible distance over the sea). In this southwest-looking view, the island of Taiwan (T) appears top left (350 km in length) and the east coast of China across the rest of the view. Topographic detail in China is degraded under the thick layer of haze. This picture was taken as the Space Shuttle flew over Okinawa-the distance to Shanghai (at the near point on the Chinese coastline, top right) is about 650 km. [NASA photographs, Hasselblad camera, 40 mm lens; (A) STS075-721-22, between February 22 and March 9, 1996, center point 27°N 105°E, altitude 296 km; (B) STS075-773-66, March 4, 1996, 01:29:47 GMT, center point 28°N 123°E, craft nadir 28°N 128.1°W, altitude 278 km.] |
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Figure 6.11
Photomosaic of haze over the Nile River Delta. Cairo, at the apex of the Nile delta in the lower half of the mosaic, is invisible beneath a blanket of haze. Under clear weather conditions, the city is visible (inset: arrows indicate north and south margins of city). Two white smoke plumes rise from the region of Helwan, south of Cairo, indicating that the ambient wind is from the west-northwest (top left towards bottom right) on this day. The regular, wavy structure on the surface of the pollution haze (top right) is transverse to the wind direction and appears to be a sequence of "gravity waves," features commonly developed between air layers of differing density (some waves are capped by small cumulus clouds, top right). South of the delta, removed from sources of the haze, the green floor of the Nile valley and the Faiyum depression (bottom left) appear distinctly clearer. [Mosaic of NASA photographs taken August 5, 1997, Hasselblad camera, 250 mm lens, altitude 383 km; NASA5-707-53 (upper), 15:39:01 GMT, center point 30.5°N 31°E, craft nadir 30.5°N 36.0°E; NASA5-707-52 (lower), 15:38:46 GMT, center point 30°N 31°E, craft nadir 29.8°N 35.2°E. Inset STS084-310-36, May 22, 1997, 05:49:49 GMT, center point 45°N 10°E, craft nadir 45.9°N 14.5°E, Hasselblad camera, 100 mm lens, altitude 372 km.] |
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Figure 6.12
Anticyclonic circulation of the atmosphere over southern Africa typically evacuates pollutants offshore to the southeast (another evacuation route lies over Angola). Footprint of the oblique, west-looking photograph shown in Figure 13 is indicated. Note that cyclonic/anticyclonic motions in the Southern Hemisphere display opposite rotations to those in the Northern Hemisphere. (Modified from Garstang et al., 1996). |
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Figure 6.13
Highly discrete corridor of aerosols streaming off the southeast coast of South Africa (foreground) on July 31, 1997 (13:48:14 GMT). The southern coast of Africa occupies the middle of this west-looking view, with Cape Point (near Cape Town) in the distance at the angle of the coast. (NASA photograph NASA5-707-01, center point 33°S 23°E, craft nadir 33.1°S 35.7°E, Hasselblad camera, 250 mm lens, altitude 391 km.) |
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Figure 6.14
Saharan dust plume moving into the Mediterranean basin, August 8, 1998. The red arrow marks the same location and cloud mass on each image. The progression from oblique to vertical look angles shows different aspects of the aerosols. (A) Northeast-looking panorama shows the landmasses of Spain lower left (city of Almeria, left arrow) and North Africa lower right (city of Tlemcen, Algeria, right arrow). Dust obscures the Balearic Islands (Palma city on the island of Mallorca, P, and the island of Ibiza, I ). The Sahara Desert lies out of the picture right. (B) Closer view of cloud and dust mass in view (A) The cloud mass has several embedded convection cells (center right) and with apparently associated linear dust features at lower altitudes along its western margin (center, and left of red arrow). The island of Mallorca (P) is dimly visible in this more vertical view but the island of Menorca (M, 120 km east-northeast of Mallorca) remains obscured. (C) Detail of linear structure in the dust immediately beneath the edge of the largest mass of cloud [center of (B)] suggests the influence of near-surface air outflow generated by downdrafts in the storm cells. In this vertical view through less dust the island of Menorca (M) is partly visible. [NASA photographs taken August 8, 1997, Hasselblad camera, 100 mm lens, altitude 382 km: (A) NASA5-708-48, 17:29:07 GMT, center point 36.5°N 1.5°W, craft nadir 33.7°N 6.0°W; (B) NASA5-708-60, 17:30:54 GMT, center point 38°N 3°E, craft nadir 38.2°N 0.2°E; (C) NASA5-708-66, 17:31:37 GMT, center point 40°N 4.5°E, craft nadir 39.9°N 2.9°E.] |
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Figure 6.15
Visibility plots (miles) for three cities in the Mediterranean basin (Annaba, Algeria; Palma, Spain; Olbia, Italy) and one trans-Atlas city (Biskra, Algeria) for August, 1997 (National Climatic Data Center, 1998a). |
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Figure 6.16
A brown set of dust plumes over Tibet on February 12, 1997 (11:06:11 GMT), start near the Paikü Co lake (dark blue, center), where winds are mobilizing ancient lake-bottom sediments. Whiter dust plumes appear top right. The alignment of the mountain ranges controls the trajectories of the plumes. This west-looking panorama shows 700 km of snowcapped peaks of the Himalaya Mountains (down the left side of the view) and the high, cold desert plateau of Tibet in the rest of the view. The upper Brahmaputra River occupies the major valley between the dust clouds (arrows). Clouds (lower left) and smoke haze (upper left corner) appear over lower-lying valleys of Nepal which lead down to the Ganges plain. (NASA photograph NM22-759-329, center point 29°N 86°E, Hasselblad camera, 100 mm lens, altitude 376 km.) |
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Figure 6.17
Plumes of mainly light-brown dust can be seen streaming off the high, arid plains of the central Andes Mountains in this view, which looks southwest toward the Pacific Ocean and Atacama Desert of northern Chile (across the top of view). Dust plumes are injected into the westerly winds above altitudes of 4,200 m-this oblique view shows the main plume intersecting the dark Cachi massif (C) at about 6,000 m. The visible length of the major dust plume in this view is approximately 240 km. The complexity of airstream circulations is apparent: dust plumes are transported by westerly winds (flow from top right to lower left) above altitudes of 4,200 m. The stratus cloud, with an upper surface at 3,290 m, is transported by gentle southerly winds (flow from left to right). The dust itself therefore rains down onto the stratus cloud (in the region of the arrows) before finally reaching the ground. This view shows that the dust pall increases albedos over the dark land surface, but decreases albedo of the cloud. (NASA photograph STS008-46-936, August 30, 1983, center point 25.5°S 66.5°W, Hasselblad camera, 100 mm lens; altitude 311 km.) |
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Figure 6.18
Trans-Pacific dust movement from the Gobi Desert to North America. Positions of the first in a series of dust emissions from Asia are indicated by dates between April 17 and 25, 1998. Arrows indicate locations of photographs in Figure 19. The data were acquired from SeaWiFs, GMS, and three GOES satellites (modified from Husar, 1998). |
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Figure 6.19
Movement of dust from the Gobi Desert across the pacific to North America. A. Margin of the dust plume on April 22, 1998 (03:12:52 GMT), four days after the leading edge of the Gobi dust first exited Asia (arrows). The Korean Peninsula appears under cloud down the left side of this north-looking view. The coast of North Korea stretches across the top (dashed line). B. Gobi Desert dust over the northeast Pacific Ocean photographed about 2500 km north-northeast of Hawaii, on April 25, 1998 (20:59:22 GMT). Here dust was transported east (from the center of the horizon toward the lower left) over the Pacific Ocean in association with the jet stream (dense line of cloud). By this date the dust had been transported nearly 5000 km from its source in central Asia. C. Gobi Desert dust formed a prominent haze over the Pacific Northwest on April 27, 1998 (20:58:31 GMT). The densest dust is indicated in this figure (and Figure 20) by two arrows-the left arrow shows a concentration offshore and the upper center arrow shows a concentration over the Columbia Basin of Washington state. The upper right and lower center arrows in this view (and Figure 20) indicate the position of a regional dust front, north of which air over the United States and southern Canada was distinctly hazy. This view was taken from a point over Los Angeles and shows the central valley of California in the foreground. [NASA photographs, Hasselblad camera, 40 mm lens; (A) STS090-730-1, center point 40.5°N 128.5°E, craft nadir 35.3°N 132°E, altitude 251 km; (B) STS090-710-58, craft nadir 38.2°N 48.8°W, altitude 246 km; (C) STS090-739-72, center point 38°N 119.5°W, craft nadir 35.2°N 119.1°W, altitude 244 km.] |
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Figure 6.20
This GOES 10 satellite visible image was acquired less than four hours after the view shown in Figure 19 C. For features marked by arrows, see caption to Figure 6.19 C. The dust mass extended well into the High Plains states and south-central Canada (top right). Dark horizontal lines are due to data loss. (Modified from Husar, 1998.) |
