# What is atmospheric physics?

A complementary field of study to atmospheric chemistry is atmospheric physics. This discipline has to do with such issues as wave and particle physics, acoustics, spectroscopy, optics, and more. A strong command of mathematics is needed for anyone wishing to specialize in this field. The theoretical work involved has applications in satellite, radar, lidar, and other technologies.

# What is diffraction?

Diffraction is the phenomenon of how light bends around small objects or through small openings. These objects and openings have to be small enough to interfere with wavelengths of light, and so wavelengths in the red spectrum (longer wavelengths) are more affected by light in the bluer spectrum. Diffraction can cause a blurring of light, as well as causing interference in the transmission of invisible energies, such as radio waves and X-rays.

# What is refraction?

Refraction refers to how light is bent as it passes from one transparent medium to another (for example, from air to water). This happens because light travels at different speeds, depending on the medium. Refraction is the reason why we see rainbows.

Most people think of spray cans when they talk about aerosols, but to a meteorologist any liquid or solid particle suspended in air is considered an aerosol.

# What is an aerosol?

Many people, when they hear the wore "aerosol," think of a chemical aerosol spray from a can of air freshener or hair spray. The word actually applies to any solid or liquid particles suspended in air. Because they are so small, aerosols tend to float (e.g., clouds), though like everything else they are subjected to gravity, falling at a rate of about four inches (10 centimeters) every 24 hours, unless washed away more quickly by rain.

# What are evaporation and transpiration?

Evaporation, as many people know, is what happens when liquid water changes to a gaseous state, escaping into the surrounding atmosphere. The rate of evaporation can be measured using an evaporimeter. Transpiration refers to the release of water vapor from plants, but can also refer to perspiration and sweat being lost from humans and animals.

# What is convection?

Convection is the transfer of heat vertically through the atmosphere via a liquid medium (e.g. water droplets).

# What is convergence?

Convergence occurs when air masses approach each other from different directions. As the masses collide, air pressure between them goes up, which causes air to flow upwards.

# What is inversion?

When the air temperature rises with altitude rather than cooling, the condition is called an inversion.

# What is an ion?

Ions are atoms or molecules with a positive or negative charge due to differences in the number of protons (positively charged particles in an atom's nucleus) and electrons (negatively charges particles that "orbit" the nucleus). Meteorologists are interested in ions, especially with regard to the ionosphere, because they are highly reactive with other elements and chemicals in the atmosphere.

# What is plasma?

Plasma is the fourth state of matter (the other states being solid, liquid, and gas). It is formed when electrons are stripped away from atoms and a mix of free electrons and the resulting ions exist together. Plasma is found in stars, which makes it actually the most common state of matter in the universe. But plasma is also found in the solar winds that blow out from the Sun and collide with the magnetosphere. Some plasma radiation makes its way into the ionosphere, too. Lightning is also a form of plasma.

# What is the azimuth?

Used in navigation and in reporting the position of stars, planets, and other celestial bodies, the azimuth is the number of degrees between the direction of North (0°) and the direction in which the object is viewed from the perspective of the observer. In more mathematical terms, it is the angle between two vertical planes, one formed between the observer and the object observed, and the other formed by the observer and true North.