Atmospheric physics

People study the air around our world.

They use tools to see things from far away. This is called remote sensing. Some tools use light from the sun. Other tools send out their own energy.

This helps them find rain or clouds. Clouds are made of tiny water drops. They can also have bits of ice.

Sometimes, bright light flashes in the high air. These are not like the lightning we see. Scientists use many tools to learn more. They want to know how the air works.

Scientists study the air around our planet. This field is called atmospheric physics. They use math to model the air and weather.

One way they study is through remote sensing. This means gathering data from far away. They do not have to touch the object. Some tools use passive sensors. These pick up natural light from the sun. Other tools use active collection. These send out energy to scan an area.

They also study radiation. Solar radiation comes from the sun. Terrestrial radiation comes from the Earth.

Clouds are another big part of the study. Clouds are made of tiny water drops or ice. Sometimes, lightning flashes in the sky. Lightning is very hot and bright.

High in the air, scientists study aeronomy. This is the study of the upper atmosphere. They use rockets and satellites to learn about it. They even see special lights like red sprites. These are different from the lightning we see on the ground.

Atmospheric physics is a way to study the air around our world. Scientists use physics to understand how the atmosphere works. They create models to see how air moves like a fluid. These models also look at how energy moves through the sky. They even study how the air connects to the oceans. This science helps us understand the weather and our climate.

One important tool is called remote sensing. This means gathering information from a distance. Scientists do not have to touch the object they study. They might use a satellite, an aircraft, or a ship. Passive sensors are one kind of tool. They detect natural light that is already there. For example, they might pick up sunlight reflected from the Earth.

Active collection is another way to sense things. These tools send out their own energy to scan an area. Then, they measure the energy that bounces back. Radar and lidar are two examples of this. This helps scientists find the height and speed of objects. Remote sensing is very helpful for studying hard places. It can monitor glaciers in the Arctic or the Amazon Basin.

Scientists also study radiation and clouds. Solar radiation comes from the sun. Terrestrial radiation comes from the Earth's surface. Earth is much colder than the sun. Because of this, its radiation has longer wavelengths. Clouds are made of tiny water droplets or ice crystals. When these droplets combine, they create precipitation. Sometimes, this leads to lightning. Lightning is very powerful and can reach 28,000 kelvins.

High in the sky, a special science called aeronomy begins. Sydney Chapman introduced this term in 1960. Aeronomy studies the very top layers of the atmosphere. Scientists use sounding rockets and satellites to reach these heights. They look for things like red sprites and blue jets. These are special lights that happen high above the ground. This science helps us learn about the atmospheres of other planets too.

Atmospheric physics is the application of physics to the study of the atmosphere. Scientists in this field work to model Earth's atmosphere and the atmospheres of other planets. They do this by using fluid flow equations to track how air moves. They also study the radiation budget and energy transfer processes. These processes often tie into boundary systems like the oceans. To model complex weather systems, they use highly mathematical tools. These include scattering theory, wave propagation models, and cloud physics. They also rely on statistical mechanics and spatial statistics to understand atmospheric behavior.

One essential method in this field is remote sensing. Remote sensing is the acquisition of information from an object without physical contact. Scientists use devices like aircraft, spacecraft, satellites, buoys, or ships to gather data. This "stand-off" collection allows for more information than single-site sensors can provide. There are two main types of remote sensing: passive and active. Passive sensors detect natural radiation that is emitted or reflected by an object. Reflected sunlight is the most common source for these sensors. Examples include film photography, infrared sensors, and radiometers.

Active collection works differently by emitting its own energy. An instrument scans an area by sending out energy and measuring what returns. This is known as backscattering. Techniques like radar, lidar, and SODAR are used in atmospheric physics. By measuring the time delay between emission and return, scientists determine an object's location, height, speed, and direction. Remote sensing is vital for studying dangerous or inaccessible areas. It helps monitor deforestation in the Amazon Basin and climate change in the Arctic and Antarctic. It also allows for the study of ocean depths without disturbing the environment.

Radiation is another central focus of atmospheric physics. Physicists divide radiation into solar radiation and terrestrial radiation. Solar radiation is emitted by the sun and contains many wavelengths. Visible light falls between 0.4 and 0.7 micrometers. Shorter wavelengths are called ultraviolet (UV), while longer ones are infrared. Ozone is very effective at absorbing UV radiation around 0.25 micrometers. This absorption increases the temperature of the stratosphere. Interestingly, different surfaces reflect UV rays differently. Snow reflects 88% of UV rays, while water reflects only 4%.

Terrestrial radiation is emitted by the Earth's surface and atmosphere. Because Earth is much colder than the sun, this radiation has much longer wavelengths. According to Planck's law, the wavelength of maximum energy for Earth is around 10 micrometers. Scientists also study cloud physics to understand how clouds form and grow. Clouds consist of microscopic water droplets, tiny ice crystals, or a mixed phase of both. Under certain conditions, these droplets combine to form precipitation. While the exact mechanics are not fully understood, researchers study the microphysics of individual droplets to build theories.

Atmospheric electricity involves the electrostatics and electrodynamics of the atmosphere. The Earth's surface, the atmosphere, and the ionosphere form the global atmospheric electrical circuit. Lightning is a major part of this system. A single lightning discharge can release 30,000 amperes and up to 100 million volts. It emits light, radio waves, X-rays, and even gamma rays. The plasma temperatures in lightning can approach 28,000 kelvins. Scientists also study atmospheric tides, which are regular fluctuations in wind, temperature, density, and pressure. Unlike ocean tides driven by the Moon, atmospheric tides are mostly generated by solar heating in the troposphere and stratosphere.

At the highest levels, the science of aeronomy begins. The term aeronomy was introduced by Sydney Chapman in 1960. It concerns the upper layers of the atmosphere where dissociation and ionization are important. Researchers use sounding rockets, balloons, and satellites to study these regions. They observe unique phenomena like red sprites, sprite halos, blue jets, and elves. Aeronomy also includes studying the atmospheres of other planets. This research is supported by many organizations, such as NOAA in the United States and the Met Office in the UK. By connecting these different layers and processes, atmospheric physics provides a complete picture of our planet's life-support system.