Meteorology

views updated

Meteorology

Introduction

Meteorology is the science that deals with the structure and dynamics of the atmosphere, especially as it relates to weather. Where Earth's atmosphere interacts with the oceans, the science of weather incorporates information about atmosphere-ocean systems and the hydrologic cycle—the natural circulation of water on Earth. Meteorology also includes a study of air pressure and temperature as variables that relate to winds, air masses, and weather fronts. Meteorologists not only forecast the weather on a short-term basis, but also attempt to explain why and how the weather changes over time.

The study of weather on a long-term basis is often called climatology rather than meteorology. Climate refers to the expected or general weather conditions over periods of years or longer. Although it is determined by the same variables as weather—temperature, precipitation, winds, and humidity—a region's climate is more than an average of these variables. It includes weather extremes, as well as the general range of expected weather. Neither weather nor climate is limited by national boundaries.

Human causes of climate change—such as the emissions from a single fossil-fuel power plant—may start slowly and affect only local weather for a time. However,

the cumulative effects of the emissions from many power plants over many years may result in a global climate change. According to the World Meteorological Organization (WMO), weather, climate, and water-related events are responsible for nearly 90% of all natural disasters.

Historical Background and Scientific Foundations

Meteorologists study Earth's major atmospheric circulation patterns that are, in part, produced as a result of uneven heating of the atmosphere between the poles and the equator. The circulation pattern is modulated by the tilt of Earth's axis, which causes changing seasons. Another cause of atmospheric circulation is the fact that land and water absorb and reflect the sun's radiation at different rates. These variables produce global atmospheric circulation patterns that are interrelated with ocean circulation.

Strong repeating atmospheric-oceanic circulation patterns oscillate in major regions of the globe, affecting local weather systems and, in the long term, climate changes. One of the most dominant is the El Niño/ Southern Oscillation that brings rain to the U.S. Pacific coast and droughts to Australia.

El Niño is a warmer than normal ocean surface temperature effect that alternates with La Niña, a colder than normal ocean surface temperature. La Niña is characterized by persistent rains in Indonesia and northern Australia. There usually are several years of normal temperatures between the two events.

Scientists expect changes in oscillation patterns as a result of climate change, but they do not yet know what these changes will be. Satellite data and computer model technology are being used to study Earth's changing climate.

Instruments have been used to collect data about the weather since Italian scientists developed a thermometer and, at about the same time, Evangelista Torricelli (1608–1647), another Italian scientist, invented the first barometer to measure air pressure. However, continuous scientific records of weather data go back only to the 1800s. Not until 1972, when the U.S. National Aeronautics and Space Administration (NASA) launched Landsat 1, the first of a series of Earth Resources Satellites, were data collected on a broad scale about Earth.

The Landsat satellites take digital photographs in visible and infrared wavelengths of land and coastal regions. They are not designed to collect weather data. However, the Landsat program has accumulated a 15-year photo record of vegetation and water resources that has become very useful for the study of climate trends.

WORDS TO KNOW

BUOYS: Tethered or free-floating devices that bear navigational aids, instruments, and in some cases radio equipment for automatically collecting and reporting data on oceanic and atmospheric conditions. Buoys may float on or beneath the surface, depending on their purpose.

CLIMATE: The average weather (usually taken over a 30-year time period) for a particular region and time period. Climate is not the same as weather, but rather, it is the average pattern of weather for a particular region. Weather describes the short-term state of the atmosphere. Climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and hail storms, and other measures of the weather.

EL NIÑO/SOUTHERN OSCILLATION: Global climate cycle that arises from interaction of ocean and atmospheric circulations. Every 2 to 7 years, westward-blowing winds over the Pacific subside, allowing warm water to migrate across the Pacific from west to east. This suppresses normal upwelling of cold, nutrient-rich waters in the eastern Pacific, shrinking fish populations and changing weather patterns around the world.

FOSSIL FUELS: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are non-renewable on the timescale of human civilization, because their natural replenishment would take many millions of years.

HYDROLOGIC CYCLE: The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30% of the mid-latitudes' heat transport from the equatorial to polar regions.

LA NIÑA: A period of stronger-than-normal trade winds and unusually low sea-surface temperatures in the central and eastern tropical Pacific Ocean; the opposite of El Niño.

In the 1980s, NASA started the Earth Observing System (EOS) to use satellites specifically to collect data with sensors to observe land, oceans, the atmosphere, and radiant energy. Three coordinated orbits are being used with instruments supplied by scientists from Canada, France, Brazil, Russia, and Japan included in the studies. Some scientists have criticized the NASA programs bysuggesting that the data being collected by NASA through the EOS satellites are only useful for short-term weather forecasting and not useful for long-range climate studies.

Since oceans make up about 70% of Earth's surface area, direct measurements at ocean surfaces are important for both weather forecasting and long-term climate research. Scientists need measurements of rising oceans, glacial melting, ocean temperatures, wave and wind speeds and direction, and air pressure above the ocean surfaces.

Buoys are deployed in coastal and offshore waters to collect and transmit information on air pressure, wind direction, speed and gusts, air and sea temperatures, and wave energy data. An array of 70 moored buoys is deployed in the tropical Pacific Ocean to send statistics on the ocean and weather to shore via a satellite system maintained by the U.S. National Oceanic and Atmospheric Administration (NOAA). Volunteer ships are equipped with sensors on their hulls that also are used for direct measurements at sea level as they travel around the globe.

Impacts and Issues

At the end of the nineteenth century, a number of leading scientists, including Swedish chemist and Noble laureate Svante Arrhenius (1859–1927), speculated on climate changes through history that produced ice ages for some periods and widespread tropical climates in other periods. The presence or absence of excess carbon dioxide in the atmosphere was thought to explain the climate changes.

Arrhenius calculated temperature on Earth from a formula for the equilibrium between solar radiation and Earth's radiation from ground and the effect of oceanic or atmospheric currents. He then calculated an increase in global temperature that would result with varying amounts of increased carbon dioxide in the atmosphere. The source of great excesses of carbon dioxide in the atmosphere was the question that could not be answered in 1900.

The source of increasing excesses of carbon dioxide in the atmosphere in the twenty-first century is not in question. A century after Arrhenius speculated on past global warming events, scientists have hard data to document global warming and changes in weather patterns that are the result of carbon dioxide accumulating in the atmosphere from the burning of fossil fuels. The impact of meteorological data collected from climate studies has been a widespread acceptance of global warming and the need to reduce carbon dioxide emissions. Unless this is done, global warming will continue with potentially weather-related catastrophic consequences.

Scientists from the World Meteorological Organization (WMO), an agency of the United Nations, provide information on Earth's global weather and its relation to atmosphere and oceanic variables that control the weather and lead to climate change. In 1988, the Inter-governmental Panel on Climate Change (IPCC) was established by the United Nations and co-sponsored by WMO. It assesses the data collected about the changing atmosphere and oceans, and from that data provides information on the global socio-economic impacts of climate changes.

BIBLIOGRAPHY

Web Sites

Arrhenius, Svante. “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” Lemoyne College, Department of Chemistry. <http://web.lemoyne.edu/~giunta/ARRHENIUS.HTML> (accessed September 1, 2007).

“Climate.” World Meteorological Organization. <http://www.wmo.ch/pages/themes/climate/index_en.html> (accessed September 1, 2007).

“Persistent Patterns that Shape Weather and Climate Variability—A Glossary.” UCAR: The University Corporation for Atmospheric Research. <http://www.ucar.edu/news/backgrounders/patterns.shtml> (accessed September 1, 2007).

“Satellites Let Scientists View Earth as Integrated System.” USINFO.STATE.GOV, August 31, 2007. <http://usinfo.state.gov/xarchives/display.html?p=washfile-english&y=2007&m=August&x=20070831140026lcnirellep0.619137> (accessed September 1, 2007).

“Weather.” World Meteorological Organization. <http://www.wmo.ch/pages/themes/weather/index_en.html> (accessed September 1, 2007).

“What's the Difference Between Weather and Climate?” U.S. National Aeronautics and Space Administration. <http://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html> (accessed September 1, 2007).

Climate Change: In Context