Atmospheric Science and Structure

Vocabulary flashcards covering the structure, composition, atmospheric layers, and key physical properties of Earth's atmosphere based on the lecture transcript by Engr. Archie Duldulao.

Atmosphere

A vital layer of gases surrounding Earth, held in place by gravity, extending from the surface into outer space to support life, regulate temperature, shield against solar radiation, and enable weather phenomena.

Troposphere

The lowest atmospheric layer, extending from Earth's surface to about 8–15 km (0 to 10 miles), containing approximately 75% of atmospheric mass and nearly all water vapor, where clouds, storms, and weather occur.

Stratosphere

The atmospheric layer extending from about 15 km to 50 km (11 to 31 miles) above the troposphere, where temperature increases with altitude due to ultraviolet radiation absorption by the ozone layer.

Mesosphere

The atmospheric layer stretching from 50 km to 85 km (32 to 85 miles), characterized by temperatures decreasing with height to as low as –90°C, making it the coldest layer where meteors burn up.

Thermosphere

The atmospheric layer ranging from 85 km to 600 km (86 to 372 miles), where temperatures rise above 1,500°C due to intense solar radiation absorption, and where auroras occur and the ISS resides.

Exosphere

The outermost atmospheric layer beginning around 600 km (310–620 miles and above) that merges into space, containing extremely sparse hydrogen and helium atoms that rarely collide.

Lapse Rate

The average rate at which temperature decreases with altitude in the troposphere, measured at 6.51°C per km (or 6.5°C per km).

Temperature Inversion

A phenomenon in the stratosphere where temperature increases with altitude due to the absorption of ultraviolet radiation by the ozone layer, creating atmospheric stability.

Kármán Line

The boundary located within the thermosphere layer that marks the start of outer space.

Nitrogen ($N_2$)

The most abundant permanent gas in the atmosphere (78%), which is chemically inert and acts as a stabilizer by diluting oxygen and reducing rapid combustion risk.

Oxygen ($O_2$)

The second most abundant atmospheric gas (21%), essential for respiration and combustion, actively cycled through photosynthesis and respiration.

Argon

A chemically inert noble gas that makes up about 0.93% of Earth's atmosphere.

Water Vapor

A variable gas (0–4%) concentrated in the lower atmosphere, essential for the hydrological cycle, weather formation, and heat trapping as a greenhouse gas.

Carbon Dioxide ($CO_2$)

A variable greenhouse gas present at approximately 0.04% concentration, essential for photosynthesis and climate regulation.

Ozone Layer

A region concentrated in the stratosphere made of ozone ($O_3$) that protects terrestrial life by absorbing harmful ultraviolet (UV) radiation.

Aerosols and Particulates

Tiny suspended solid or liquid particles such as dust, pollen, sea salt, volcanic ash, and pollutants that serve as condensation nuclei for clouds and impact climate.

Standard Atmospheric Pressure

The weight of the air column above a given point, defined at standard sea level as 1013.25 hPa (hectopascals) or 1 atmosphere (atm).

Standard Atmospheric Density

The average mass of air per unit volume at sea level under standard conditions, equal to $1.225\,\text{kg/m}^3$.

Ideal Gas Law for Air Density

The equation $\rho = \frac{P}{R\,T}$ where $\rho$ represents density, $P$ is pressure, $T$ is temperature, and $R$ is the gas constant.

Density Altitude

An aviation condition occurring at high altitudes or on hot days where reduced air density lowers aircraft engine power output and wing lift, requiring longer takeoff distances.

Auroras

The Northern and Southern Lights produced in the thermosphere when charged solar particles interact with atmospheric gases.