Meteorology
Meteorology is the study of the atmosphere, atmospheric
phenomena, and atmospheric effects on our weather. The atmosphere is
the gaseous layer of the physical environment that surrounds a planet.
Earth’s atmosphere is roughly 100 to 125 kilometers (65-75 miles)
thick. Gravity keeps the atmosphere from expanding much farther.
Meteorology is a subdiscipline of the atmospheric sciences, a term that
covers all studies of the atmosphere. A subdiscipline is a specialized field of
study within a broader subject or discipline. Climatology
and aeronomy are also subdisciplines of the atmospheric sciences.
Climatology focuses on how atmospheric changes define and alter the
world’s climates. Aeronomy is the study of the upper parts of the
atmosphere, where unique chemical and physical processes occur. Meteorology
focuses on the lower parts of the atmosphere, primarily the troposphere,
where most weather takes place.
Meteorologists use scientific principles to observe, explain,
and forecast our weather. They often focus on atmospheric research or
operational weather forecasting. Research meteorologists cover several
subdisciplines of meteorology to include: climate modeling, remote sensing, air
quality, atmospheric physics, and climate change. They also research the
relationship between the atmosphere and Earth’s climates, oceans, and
biological life.
Forecasters use that research, along with atmospheric data, to scientifically
assess the current state of the atmosphere and make predictions of its future
state. Atmospheric conditions both at the Earth's surface and above are
measured from a variety of sources: weather stations, ships, buoys,
aircraft, radar, weather balloons, and satellites. This data
is transmitted to centers throughout the world that produce computer
analyses of global weather. The analyses are passed on to national and regional
weather centers, which feed this data into computers that model the future
state of the atmosphere. This transfer of information demonstrates how weather
and the study of it take place in multiple, interconnected ways.
Scales of Meteorology
Weather occurs at different scales of space and time. The four meteorological
scales are: microscale, mesoscale, synoptic scale, and global scale.
Meteorologists often focus on a specific scale in their work.
Microscale Meteorology
Microscale meteorology focuses on phenomena that
range in size from a few centimeters to a few kilometers, and that have short
life spans (less than a day). These phenomena affect very small geographic
areas, and the temperatures and terrains of those areas.
Microscale meteorologists often study the processes that occur between
soil, vegetation, and surface water near ground level. They measure the
transfer of heat, gas, and liquid between these surfaces. Microscale
meteorology often involves the study of chemistry.
Tracking air pollutants is an example of microscale meteorology. MIRAGE-Mexico
is a collaboration between meteorologists in the United States and Mexico. The
program studies the chemical and physical transformations of gases
and aerosols in the pollution surrounding Mexico City. MIRAGE-Mexico uses
observations from ground stations, aircraft, and satellites to track
pollutants.
Mesoscale Meteorology
Mesoscale phenomena range in size from a few kilometers to roughly 1,000
kilometers (620 miles). Two important phenomena are mesoscale convective
complexes (MCC) and mesoscale convective systems (MCS). Both are caused
by convection, an important meteorological principle.
Convection is a process of circulation. Warmer, less-dense fluid
rises, and colder, denser fluid sinks. The fluid that most
meteorologists study is air. (Any substance that flows is considered a fluid.)
Convection results in a transfer of energy, heat, and moisture—the basic
building blocks of weather.
In both an MCC and MCS, a large area of air and moisture is warmed during the
middle of the day—when the sun angle is at its highest. As this warm air mass
rises into the colder atmosphere, it condenses into clouds, turning
water vapor into precipitation.
An MCC is a single system of clouds that can reach the size of the state of
Ohio and produce heavy rainfall and flooding. An MCS is a smaller cluster of
thunderstorms that lasts for several hours. Both react to unique transfers of
energy, heat, and moisture caused by convection.
The Deep Convective Clouds and Chemistry (DC3) field campaign is a program that
will study storms and thunderclouds in Colorado, Alabama, and Oklahoma. This
project will consider how convection influences the formation and movement of
storms, including the development of lightning. It will also study their impact
on aircraft and flight patterns. The DC3 program will use data gathered from
research aircraft able to fly over the tops of storms.
Synoptic Scale Meteorology
Synoptic-scale phenomena cover an area of several hundred or even thousands of
kilometers. High- and low-pressure systems seen on local weather forecasts,
are synoptic in scale. Pressure, much like convection, is an important
meteorological principle that is at the root of large-scale weather systems as
diverse as hurricanes and bitter cold outbreaks.
Low-pressure systems occur where the atmospheric pressure at the surface of the
Earth is less than its surrounding environment. Wind and moisture from areas
with higher pressure seek low-pressure systems. This movement, in conjunction
with the Coriolis force and friction, causes the system to rotate counter-clockwise
in the Northern Hemisphere and clockwise in the Southern Hemisphere, creating
a cyclone. Cyclones have a tendency for upward vertical motion. This
allows moist air from the surrounding area to rise, expand and condense into
water vapor, forming clouds. This movement of moisture and air causes the
majority of our weather events.
Hurricanes are a result of low-pressure systems (cyclones) developing over
tropical waters in the Western Hemisphere. The system sucks up massive amounts
of warm moisture from the sea, causing convection to take place, which in turn
causes wind speeds to increase and pressure to fall. When these winds reach
speeds over 119 kilometers per hour (74 miles per hour), the cyclone is
classified as a hurricane.
Hurricanes can be one of the most devastating natural disasters in the
Western Hemisphere. The National Hurricane Center, in Miami, Florida,
regularly issues forecasts and reports on all tropical weather systems. During
hurricane season, hurricane specialists issue forecasts and warnings for every
tropical storm in the western tropical Atlantic and eastern tropical Pacific.
Businesses and government officials from the United States, the Caribbean,
Central America, and South America rely on forecasts from the National Hurricane
Center.
High-pressure systems occur where the atmospheric pressure at the
surface of the Earth is greater than its surrounding environment. This pressure
has a tendency for downward vertical motion, allowing for dry air and clear
skies.
Extremely cold temperatures are a result of high-pressure systems that develop
over the Arctic and move over the Northern Hemisphere. Arctic air is very cold
because it develops over ice and snow-covered ground. This cold air is so dense
that it pushes against Earth’s surface with extreme pressure, preventing any
moisture or heat from staying within the system.
Meteorologists have identified many semi-permanent areas of high-pressure. The
Azores high, for instance, is a relatively stable region of high pressure
around the Azores, an archipelago in the mid-Atlantic Ocean. The Azores high is
responsible for arid temperatures of the Mediterranean basin, as well as
summer heat waves in Western Europe.
Global Scale Meteorology
Global scale phenomena are weather patterns related to the
transport of heat, wind, and moisture from the tropics to the poles. An
important pattern is global atmospheric circulation, the large-scale movement
of air that helps distribute thermal energy (heat) across the surface of the
Earth.
Global atmospheric circulation is the fairly constant movement of winds
across the globe. Winds develop as air masses move from areas of high
pressure to areas of low pressure. Global atmospheric circulation is largely
driven by Hadley cells. Hadley cells are tropical and equatorial
convection patterns. Convection drives warm air high in the atmosphere, while
cool, dense air pushes lower in a constant loop. Each loop is a Hadley cell.
Hadley cells determine the flow of trade winds, which meteorologists
forecast. Businesses, especially those exporting products across oceans, pay
close attention to the strength of trade winds because they help ships travel
faster. Westerlies are winds that blow from the west in
the midlatitudes. Closer to the Equator, trade winds blow from the
northeast (north of the Equator) and the southeast (south of the Equator).
Meteorologists study long-term climate patterns that disrupt global atmospheric
circulation. Meteorologists discovered the pattern of El Nino, for
instance. El Niño involves ocean currents and trade winds across the
Pacific Ocean. El Niño occurs roughly every five years, disrupting global
atmospheric circulation and affecting local weather and economies from
Australia to Peru.
El Niño is linked with changes in air pressure in the Pacific Ocean
known as the Southern Oscillation. Air pressure drops over the eastern
Pacific, near the coast of the Americas, while air pressure rises over the
western Pacific, near the coasts of Australia and Indonesia. Trade winds weaken.
Eastern Pacific nations experience extreme rainfall. Warm ocean currents
reduce fish stocks, which depend on nutrient-rich upwelling of
cold water to thrive. Western Pacific nations experience drought,
devastating agricultural production.
Understanding the meteorological processes of El Niño helps farmers, fishers,
and coastal residents prepare for the climate pattern.
History of Meteorology
The development of meteorology is deeply connected to developments
in science, math, and technology. The Greek philosopher Aristotle
wrote the first major study of the atmosphere around 340 BCE. Many of
Aristotle’s ideas were incorrect, however, because he did not believe it was
necessary to make scientific observations.
A growing belief in the scientific method profoundly changed the
study of meteorology in the 17th and 18th centuries. Evangelista Torricelli, an
Italian physicist, observed that changes in air pressure were connected to
changes in weather. In 1643, Torricelli invented the barometer, to
accurately measure the pressure of air. The barometer is still a key instrument
in understanding and forecasting weather systems. In 1714, Daniel Fahrenheit, a
German physicist, developed the mercury thermometer. These instruments made it
possible to accurately measure two important atmospheric variables.
There was no way to quickly transfer weather data until the invention of the
telegraph by American inventor Samuel Morse in the mid-1800s. Using this new
technology, meteorological offices were able to share information and produce
the first modern weather maps. These maps combined and displayed more complex
sets of information such as isobars (lines of equal air pressure)
and isotherms (lines of equal temperature). With these large-scale weather
maps, meteorologists could examine a broader geographic picture of weather and
make more accurate forecasts.
In the 1920s, a group of Norwegian meteorologists developed the concepts of air
masses and fronts that are the building blocks of modern weather
forecasting. Using basic laws of physics, these meteorologists discovered that
huge cold and warm air masses move and meet in patterns that are the root of
many weather systems.
Military operations during World War I and World War II brought great advances
to meteorology. The success of these operations was highly dependent on weather
over vast regions of the globe. The military invested heavily in training,
research, and new technologies to improve their understanding of weather. The
most important of these new technologies was radar, which was developed to
detect the presence, direction, and speed of aircraft and ships. Since the end
of World War II, radar has been used and improved to detect the presence,
direction, and speed of precipitation and wind patterns.
The technological developments of the 1950s and 1960s made it easier and faster
for meteorologists to observe and predict weather systems on a massive scale.
During the 1950s, computers created the first models of atmospheric
conditions by running hundreds of data points through complex equations. These
models were able to predict large-scale weather, such as the series of high-
and low-pressure systems that circle our planet.
TIROS I, the first meteorological satellite, provided the first accurate
weather forecast from space in 1962. The success of TIROS I prompted the
creation of more sophisticated satellites. Their ability to collect and
transmit data with extreme accuracy and speed has made
them indispensable to meteorologists. Advanced satellites and the
computers that process their data are the primary tools used in
meteorology today.
Meteorology Today
Today’s meteorologists have a variety of tools that help them examine,
describe, model, and predict weather systems. These technologies are being
applied at different meteorological scales, improving forecast accuracy and
efficiency.
Radar is an important remote sensing technology used in forecasting. A radar
dish is an active sensor in that it sends out radio waves that bounce off
particles in the atmosphere and return to the dish. A computer processes these
pulses and determines the horizontal dimension of clouds and precipitation, and
the speed and direction in which these clouds are moving.
A new technology, known as dual-polarization radar, transmits both
horizontal and vertical radio wave pulses. With this additional pulse,
dual-polarization radar is better able to estimate precipitation. It is also
better able to differentiate types of precipitation—rain, snow, sleet, or hail.
Dual-polarization radar will greatly improve flash-flood and winter-weather
forecasts.
Tornado research is another important component of meteorology. Starting
in 2009, the National Oceanic and Atmospheric Administration (NOAA) and the
National Science Foundation conducted the largest tornado research project in
history, known as VORTEX2. The VORTEX2 team, consisting of about 200 people and
more than 80 weather instruments, traveled more than 16,000 kilometers (10,000
miles) across the Great Plains of the United States to collect data
on how, when, and why tornadoes form. The team made history by collecting
extremely detailed data before, during, and after a specific tornado. This
tornado is the most intensely examined in history and will provide key insights
into tornado dynamics.
Satellites are extremely important to our understanding of global scale weather
phenomena. The National Aeronautics and Space Administration (NASA) and NOAA
operate three Geostationary Operational Environmental Satellites (GOES) that
provide weather observations for more than 50 percent of the Earth’s surface.
GOES-15, launched in 2010, includes a solar X-ray imager that
monitors the sun’s X-rays for the early detection of solar phenomena, such
as solar flares. Solar flares can affect military
and commercial satellite communications around the globe. A highly
accurate imager produces visible and infrared images of Earth’s surface,
oceans, cloud cover, and severe storm developments. Infrared imagery detects
the movement and transfer of heat, improving our understanding of the global
energy balance and processes such as global warming, convection, and
severe weather.
Hadley cells are the basis for our understanding of global-scale meteorology.