Meteorology

Summary

Meteorology is the interdisciplinary study of physical phenomena occurring at various levels of Earth's atmosphere. Practical applications of meteorological findings all relate in some way to understanding longer-term weather conditions. On the whole, however, meteorological weather forecasts are mainly short-term in nature, in contrast to the research goals of climatology. They concentrate on contributing factors, including temperature, humidity, atmospheric pressure, and winds.

Definition and Basic Principles

Meteorology is the study of Earth's atmosphere, particularly changes in atmospheric conditions. The three main factors affecting change in the atmosphere are humidity, temperature, and barometric pressure. Dynamic short-term interaction among these three atmospheric factors produces the various phenomena associated with changeable weather. Low barometric pressure conditions are generally associated with a greater capacity for the atmosphere to absorb water vapor, resulting in various cloud formations, whereas high pressure prevents humidity absorption.

Meteorological calculation of relative humidity, for example, reveals how much more moisture can be absorbed by the atmosphere at specific temperature levels before reaching the saturation point. Changes in temperature in either direction will affect this dynamic process. Rainfall occurs when colder air pushes warmer, moisture-laden air upward into higher altitudes, where the warmer air mass begins to cool. Cooler air cannot hold as much water as warmer air, so the relative humidity of the warmer air mass changes, resulting in condensation and precipitation. This phenomenon is closely associated with the presence of surface winds.

Background and History

Meteorology, like several other applied sciences that stem from observations of natural phenomena, has a long history. The term “meteorology” comes from the Greek word for “high in the sky.” Aristotle's work on meteorology maintained that the sun attracted two masses of air from the earth's surface, one humid and moist (which returned as rain) and the other hot and dry (the source of wind currents). His student Theophrastus described distinct atmospheric signs associated with eighty types of rain, forty-five types of wind, and fifty storms.

During the Renaissance, Europeans developed instruments to refine these ancient Greek theories. The Italian scientist Galileo, for example, used a closed glass container with a system of gauges that showed how air expands and contracts at different temperatures (the principle of the thermometer). The French philosopher Blaise Pascal developed what became the barometer, a device to measure surrounding atmospheric pressure levels.

Although many important small-scale experiments would be carried out in the eighteenth and nineteenth centuries, a breakthrough occurred in the first quarter of the twentieth century when Norwegian physicist and meteorologist Vilhelm Bjerknes and his son, Jacob Bjerknes, developed the theory of atmospheric fronts, involving large-scale interactions between cold and warmer air masses close to the earth's surface. In the 1920s, a Japanese meteorologist first identified what came to be known as jet streams, or fast-moving air currents at altitudes between approximately 23,000 and 52,000 feet.

The turning point for modern meteorology came in April 1960, when the United States (US)launched TIROS 1, the first in a series of meteorological satellites. This revolutionary tool enabled scientists to study atmospheric phenomena, such as radiation flux and balance, that were known but had yet to be measured with high levels of accuracy.

How It Works

Meteorologists employ various basic tools and methods to obtain the data needed to put together a comprehensive picture of local or regional atmospheric conditions and changes. At the most basic level, meteorologists focus on three essential factors affecting the atmosphere: temperature, air pressure, and humidity.

Drawing on empirical data, meteorologists analyze the effects of these three factors in the area of the atmosphere they are studying and then apply their findings to ever-widening areas of the globe. From their analyses, they can predict weather events, such as the direction and strength of the wind and the nature and the probable intensity of storms heading toward an area, even if they are still thousands of miles away.

Wind Strength and Direction. Like rain and snowstorms, wind is a common weather phenomenon, but its meteorological explanations are somewhat complicated. All local or global winds are the product of various atmospheric pressure patterns. The most common horizontal winds arise when a low-pressure area draws air from a higher-pressure zone.

However, meteorologists must gather much more than simple barometric data to build a complete picture of the likely strengths and directions of winds. They must consider, for example, the dynamics of the Coriolis effect, which is the influence of Earth's rotation on moving air. Except along the specific latitude of the equator, the Coriolis effect, which is weaker near the equator and stronger near the poles, makes winds appear to curve in a circular pattern relative to the planet's surface. Normal curving from the Coriolis effect results from another force, the centrifugal force caused by Earth's rotation, being out of balance with Earth's gravitational force. When wind is curving around a low-pressure area, the centrifugal force is negligible, and the air rotates in the same direction as the apparent rotation of the earth; when circling a high-pressure area, the centrifugal force is predominant, and it moves in the opposite direction. Tornadoes and hurricanes occur when centrifugal acceleration reaches very high levels.

When a near balance exists between the Coriolis effect and centrifugal acceleration, the resultant (still somewhat curved) wind pattern is called cyclostrophic. If no frictional drag (deceleration associated with physical obstacles at lower elevations) exists, something close to a straight wind pattern occurs, especially at altitudes of about two-thirds of a mile and greater. This straight wind, called a geostrophic wind, is characterized by a balance between the pressure gradient and the Coriolis effect.

In some parts of the Northern Hemisphere, massive changes in pressure gradient produced by differences in the temperature of the land and the ocean create monsoon winds (typically reversed from season to season) are followed by storms and heavy rains in the summer. The best-known monsoon system is the Indian monsoon, where the rising heat of summer creates a subcontinent-wide thermal low-pressure zone, which attracts the moisture-laden air from the Indian Ocean into cyclonic wind patterns and much-needed, though sometimes catastrophic, heavy rainfall.

Atmospheric Absorption and Transfer of Heat. Meteorologists worldwide use various methods to determine how much heat from the sun (solar radiation) reaches the Earth's surface. Heat values for solar radiation are calculated in relation to a universal reference, the solar constant. The solar constant (1.37 kilowatts of energy per square meter) represents the density of radiation at Earth's mean distance from the sun at the point just before the sun's heat (shortwave infrared waves) enters Earth's atmosphere. Not all this heat actually reaches Earth's surface. The actual amount is determined by various factors, including latitudinal location, the degree of cloud cover, and the presence in the atmosphere of trace gases that can absorb radiation, such as argon, ozone, sulfur dioxide, and carbon dioxide.

At the same time, data must be gathered to calculate the amount of heat leaving Earth's surface, mainly in the form of (longwave) infrared rays. Meteorologists attempt to calculate ecologically appropriate energy budgets, first on a global scale and then for specific geographic locations.

Cyclones.Cyclones include several forms of severe weather, the most violent of which is known as a tornado. Cyclones are characterized by circular or turning patterns of air centered on a zone of low atmospheric pressure. The direction of cyclone rotation is the same as the rotation of the earth—that is, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Frontal cyclones, the most common type, usually develop in association with low-pressure troughs that form along the polar front, which separates arctic and polar air masses from tropical air masses. Typical cyclogenesis occurs when moisture-laden air above the center of a relatively warm low-pressure area begins to rotate under the influence of converging or diverging winds at the surface or higher levels. Simply stated, the dynamic forces operating within a cyclone can pull broad weather fronts toward them, causing increasingly strong winds and precipitation. Anticyclones occur under opposite conditions, originating in high-pressure areas where air masses are pushed down from upper areas of the atmosphere.

Applications and Products

Meteorology has practical and professional scientific applications. Everyday weather reports are the most common application of meteorology. Weather reports and forecasts are available through traditional sources, such as the Internet, newspapers, television, and radio broadcasts. They can be obtained by calling the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service. Real-time weather reports, including radar, and hourly, daily, and ten-day forecasts are available for the United States and other parts of the world. With the advent of smartphones and other smart devices, a weather forecast is immediately available to most of the population.

Knowledge of existing and forecasted weather conditions is invaluable to companies that provide public transportation, such as airlines. Knowledge of weather conditions and forecasts is essential to ensuring the safety of passengers on airplanes, trains, buses, boats, and ferries. Motorists, whether traveling for business or pleasure, must plan for weather conditions. People who participate in outdoor recreational activities or sports, such as hiking, biking, camping, hang gliding, fishing, and boating, depend on accurate forecasts to ensure that they are adequately prepared for the conditions and to avoid getting into dangerous situations. Those participating in outdoor activities and sports often purchase various meteorological instruments, such as lightning detectors, weather-alert radios, and digital weather stations, designed to keep them informed and aware.

Weather Equipment. Meteorology involves measuring temperature, air pressure, and humidity. Many companies produce equipment for this purpose, including products for home use, portable products for outdoor use, and products for industry use, such as weather balloons and satellites. Equipment ranges from simple mechanical rain gauges to digital temperature sensors to complete home weather stations. Some companies offer software that provides specific weather information promptly to companies or individuals who need it.

Scientific Applications. The World Data Center in Asheville, North Carolina, distributes meteorological data it has gathered and processed. Its facilities are open on a limited basis to visiting research scientists sponsored by recognized parent organizations or international programs. Various meteorological data are readily available on an exchange basis to counterparts of the center in other countries. One organization participating in the information exchange is the World Climate Programme, an international program headquartered in Switzerland devoted to understanding the climate system and using its knowledge to help countries dealing with climate change and variability.

Careers and Course Work

Those seeking a career in meteorology can consider a wide range of possibilities. The American Meteorological Association requires at least twenty semester credits in the sciences, including geophysics, earth science, physics, chemistry, computer science, and mathematics. Beyond such basic science courses, specialized courses in atmospheric dynamics, physical meteorology, synoptic meteorology, and hydrology represent slightly more than half the required courses. Several government agencies and private commercial businesses employ full- or part-time meteorologists to provide technical information needed to carry out their operations.

The most familiar job of a meteorologist is to prepare weather reports for broadcast on television or to be published in newspapers. The task of a weather forecaster for a local television station is more complex than it may seem, judging from the briefness of the televised forecast. Local predictions are created from data gathered from diverse sources. Often, these sources gather information for an entire region or country, such as pulse-Doppler-radar operators, who receive special training to enter the profession.

Government Agencies. Opportunities for employment in agencies that gather meteorological data are found within NOAA, part of the US Department of Commerce. NOAA contains several organizations that deal with meteorology, including the National Environmental Satellite, Data, and Information Service. This specialized satellite technology branch provides global environmental data and assessments of the environment. Another NOAA organization is the National Weather Service, which provides forecasts, maps, and information on water and air quality. The Office of Oceanic and Atmospheric Research contains the Climate Program Office, which studies climate variability and predictability.

The National Centers for Environmental Prediction, part of the National Weather Service, oversees operations by several key specialized service organizations run by professional meteorologists. The most important of these are the Hydrometeorological Prediction Center in Washington, DC; the Tropical Prediction Center, which includes the National Hurricane Center in Miami, Florida; and the Storm Prediction Center in Norman, Oklahoma, which maintains a constant tornado alert system for vulnerable geographical regions. Other operations include the Ocean Prediction Center, the Aviation Weather Center, the Climate Prediction Center, the Environmental Modeling Center, and the Space Weather Prediction Center.

Private Commercial Operations. Several private companies are involved in developing and producing instruments used for meteorological data gathering. The instruments range from simple devices to sophisticated electronic equipment complete with software. The development of new weather satellites requires instruments that can be used and make the most of the gathered information.

Social Context and Future Prospects

The worldwide need for accurate daily and short-term meteorological forecasts, delivered in various formats, necessitates the continuing development of more accurate instruments and better predictive models, as well as improved and additional methods of packaging and delivering the information to users. Accurate predictions of where extreme weather, such as hurricanes and tornadoes, will occur and how intense the storms will be can help save lives and possibly minimize economic damage. Data gathered by meteorologists are also gaining importance in analyzing global climate change issues, such as air pollution and changes in the ozone layer. The ability to gather information by satellites allowed meteorology to make significant advances, and future research is likely to focus on increasing satellites' data-sensing ability and the speed and quality of data transmission as well as on software to interpret and analyze the information.

Satellite Technology. The development of satellite technology continues to revolutionize the science of meteorology. Various types of polar-orbiting satellites have been devised since the early 1960s. The task of the satellite bus—the computer-equipped part of the satellite without sensitive recording instruments—is to transmit data gathered by an increasingly sophisticated variety of devices designed to collect vital data.

One such scanning device is the advanced very-high-resolution radiometer (AVHRR) used to measure heat radiation rising from localized areas on Earth's surface. An AVHRR, like a telescope, projects a beam split by a set of mirrors, lenses, and filters that distribute the work of data recording to several different sensor devices or channels. To obtain an accurate reading of radiation rising from a given target, the AVHRR must calibrate data received from these sensors. AVHRR technology produces images that depict the horizontal structure of the atmosphere, and another radiation-recording instrument, the high-resolution infrared radiation sounder (HIRS), produces soundings based on the vertical structure of the atmosphere.

The microwave-sounding unit (MSU) may be used in widespread cloud cover zones. The area scanned by an MSU is about a thousand times greater than that scanned by a device using infrared wavelengths. Other specialized sounding devices used by meteorological satellites include stratospheric sounding units and solar backscatter ultraviolet radiometers (SBUV), which measure patterns of solar radiation reflection coming back from the earth's surface.

The functions of SBUVs, in particular, became more and more critical as concern about changes in the composition of the ozone layer emerged in the last decades of the twentieth century. Ozone-depleting substances, such as chlorofluorocarbons (used for air-conditioning systems and as a propellant for aerosol sprays), have had a negative effect on the protective ozone layer. Ozone depletion allows increased levels of ultraviolet radiation to reach Earth, raising the incidence of skin cancer and damaging sensitive crops. Beyond the apparent utility of using satellites to predict global weather, these devices play a major role in helping meteorologists monitor the all-important radiation budget (the balance between incoming energy from the sun and outgoing thermal and reflected energy from the earth) that ultimately determines the effectiveness of the atmosphere in sustaining life on Earth.

Air Pollution. Although the presence of pollutants in the air has been recognized as an undesirable phenomenon since the onset of the Industrial Revolution, by the end of the twentieth century, the question of air quality began to take on new and alarming dimensions. As countries industrialized, the combustion of fossil fuels to power industry and later automobiles released ever-increasing amounts of solar-radiation-absorbing greenhouse gases into the atmosphere. The most alarming effects stem from carbon dioxide, but meteorologists are also concerned about other serious gaseous pollutants and various chemical particles suspended in gases (aerosols). Even if industries do not pollute by burning fossil fuels, many release sulfur dioxide, asbestos, and silica in quantities large enough to seriously damage air quality. Natural phenomena, including massive volcanic eruptions, can also produce atmospheric chemical imbalances that challenge analysis by meteorologists, and, with the acceleration of global climate change, these natural phenomena have become increasingly common.

Meteorology is also benefiting from technological advances in the twenty-first century. The development of artificial intelligence algorithms and data analytics allows meteorologists to locate weather patterns and make more accurate predictive weather models. The use of the Internet of Things through various smart devices provides accurate real-time weather data. The future of meteorology will be best explored through an interdisciplinary approach as efficiency, accuracy, and sustainability remain at its core. 

Bibliography

Budyko, Michael I., Alexander B. Ronov, and Alexander L. Yanshin. History of the Earth's Atmosphere. Berlin: Springer, 1987.

Burkhalter, Max. “The IoT Brings Convenience and Accuracy to Meteorology.” Perle Systems, 12 Mar. 2020, www.perle.com/articles/the-iot-brings-convenience-and-accuracy-to-meteorology-40188568.shtml. Accessed 3 June 2024.

Fry, Juliane L, et al. The Encyclopedia of Weather and Climate Change: A Complete Visual Guide. Berkeley: U of California P, 2010.

Grenci, Lee M., and Jon M. Nese. A World of Weather: Fundamentals of Meteorology. 5th ed. Dubuque: Kendall, 2010.

Hewitt, C. N., and Andrea Jackson, eds. Handbook of Atmospheric Science: Principles and Applications. Malden: Blackwell, 2008.

Holton, James R., and Gregory J. Hakim. An Introduction to Dynamic Meteorology. 5th ed. Waltham: Academic, 2013.

Kite-Powell, Jennifer. “How The Internet Of Things Can Help Cities React To Weather.” Forbes, 16 Apr. 2022, www.forbes.com/sites/jenniferhicks/2022/08/16/can-the-internet-of-things-change-how-cities-react-to-weather/?sh=58d7a263315e. Accessed 3 June 2024.

Lutgens, Frederick K., and Edward J. Tarbuck. The Atmosphere: An Introduction to Meteorology. 14th ed. Pearson, 2019.

Williams, Jack. The AMS Weather Book: The Ultimate Guide to America's Weather. Chicago: U of Chicago P, 2009.