Dust Cloud over Japan

Photograph

By: NASA Sea-viewing Wide Field-of-view Sensor

Date: March 25, 2002

Source: "Dust Cloud over Japan." SeaWiFS Project. NASA Goddard Space Flight Center, 2002.

About the Organization: NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is an optical instrument mounted on the OrbView-2 satellite. Launched on August 1, 1997, the major purpose of the instrument was to detect changes in the color of the oceans. From this information, the concentration and type of phytoplankton in the Earth's oceans can be determined and the role of oceanic photosynthesis in the global carbon cycle can be understood. Because SeaWiFS is an optical instrument, it also detects particulate material, such as dust and sand, in the atmosphere. SeaWiFS provides global coverage of the Earth every forty-eight hours.

INTRODUCTION

Dust and sand storms occur when strong winds lift particles into the air. Usually these storms occur coincident with a cold front that brings dynamic weather into a region. Sand storms and dust storms occur in arid or semi-arid places, as well as in places that have experienced sustained droughts or are undergoing desertification. Major sand and dust storms commonly form in central Asia, over the Sahara desert, and in the Middle East; smaller storms form over the North American prairies and the Australian deserts.

In 2004, scientists estimated that the annual transport of dust and minerals into the atmosphere is three trillion tons per year. The Sahara Desert contributes about one third of this total. Dust storms transport sediments and minerals great distances from their source. For example, dust from the central Asian deserts can reach North America, more than 3,000 miles (5,000 kilometers) away. Dust from the Sahara is swept toward Europe and even toward the eastern coast of North America.

Sand storms often appear as giant walls of sand that move horizontally with frightening speed. Sand particles are on average 0.006 to 0.01 inches (0.15 to 0.3 millimeters) in diameter, while dust particles are typically smaller. Sand storms can reach heights of about 50 feet (15 meters) with wind speeds approaching ten miles per hour (16 kilometers per hour). Dust storms form when small particles of dust are lifted up into the air by chilled downdrafts near cold fronts. These downdrafts hit the ground at speeds as fast as 50 miles per hour (80 kilometers per hour), sweeping dust to great heights. Dust storms average 3,000 to 6,000 feet (914 to 1829 meters) in height, but some may have dust suspended as high as 40,000 feet (12,192 meters) above the ground.

The satellite image below shows a large plume of dust that was swept into the air to move and cover the region of the Pacific near Japan. The dust storm appears slightly grayer than the bright white water vapor clouds in the image. The dust storm flows eastward off the continent past Japan and over the Pacific Ocean.

PRIMARY SOURCE

DUST CLOUD OVER JAPAN

See primary source image.

SIGNIFICANCE

Dust and sand storms affect the fundamental physics of the planet. They impact temperatures in the atmosphere by absorbing and scattering light energy from the Sun. Dust in the atmosphere also acts as nuclei for the formation of water droplets in clouds. Dust that is deposited in oceans serves as an important source of minerals that phytoplankton require in order to grow. When phytoplankton grow, they use carbon dioxide, removing a major greenhouse gas from the atmosphere. Therefore, dust storms can have an influence on global warming.

Sand and dust storms also have an impact on the geology of Earth. They transport more sediment than any other geological process. Dust storms are an indicator of soil erosion and desertification. The storms also raise social issues and questions about land use. The storms increase in frequency when land is disturbed by overgrazing and clearing of land for agriculture.

There is some evidence that sand and dust storms have been increasing in frequency during the last few decades. In the 1950s the Korean Meteorological Administration reported that sand storms affected the country fewer than fifteen days per year. In 2002 the number grew to more than twenty-five days per year. Some scientists also observe or argue that warmer winters are related to an increase in sand and dust storms.

Scientists have also found that the sand and dust storms are combining with pollutants in the atmosphere, like soot and vehicle exhaust, to cause health and environmental problems. The World Health Organization blames sand and dust storms in Asia for half a million premature deaths per year. Prior to sweeping out to the Pacific, the dust storm pictured in the image above raised dust levels in Seoul to twice that considered dangerous to human health. Dust from the Sahara desert that is transported across the Atlantic Ocean by storms has been found to contain harmful microorganisms. In particular, the fungi Aspergilus sydowii, which was transported by dust storms from Africa, is blamed for the death of sea fans throughout the Caribbean Coral reefs.

Sand and dust storms have economic impacts as well. During severe storms, businesses and schools are closed. Transportation suffers during low visibility periods affecting the movement of airplanes, trucks, and trains. Sand and dust storms also have a negative impact on agriculture, severely damaging crops and livestock.

In response to the threats posed by dust and sand storms, international agencies have pooled their resources to study the development and impacts of those storms. In 2004, the United Nations Environmental Programme and, in 2005, the World Meteorological Organization launched research projects for improving the understanding of the mechanisms that cause sand and dust storms. The programs seek to develop forecasting models so that early warning systems for the occurrence and intensity of sand and dust storms may be used to make health and policy decisions in areas affected by storms. In addition, the programs will monitor the global incidence of storms and develop databases so that the information can be shared among nations.

FURTHER RESOURCES

Web sites

"Dust Storms, Sand Storms and Related NOAA Activities in the Middle East." NOAA Magazine, April 7, 2003. 〈http://www.magazine.noaa.gov/stories/mag86.htm〉 (accessed March 17, 2006).

Goudie, A.S., N. Lancaster, R.E. Vance, et al. "Dust Transport: Geoindicator." International Union of Geological Sciences, revised March 2004. 〈http://www.lgt.lt/geoin/doc.php?did=cl_dustra〉 (accessed March 17, 2006).

Kirby, Alex. "Asia's Dust Storm Misery Mounts." BBC News, march 31, 2004. 〈http://news.bbc.co.uk/1/hi/sci/tech/3585223.stm〉 (accessed March 17, 2006).

Wind Erosion Research Unit (WERU), United States Department of Agriculture, Agriculture Research Service in cooperation with Kansas State University. 〈http://www.weru.ksu.edu/new_weru/index.html〉 (accessed March 17, 2006).

"Report of the Seventh Session of the Science Steering Committee for the WWRP (October 19-23, 2004)." World Meteorological Organization: World Weather Research Programme, 2005. 〈http://www.wmo.ch/web/arep/wwrp/PUBLI/WWRP_8.pdf〉 (accessed March 17, 2006).