Exploring Earth’s Atmosphere: Layers, Variables, and Phenomena
Earth’s Atmosphere
Atmospheric Layers
The atmosphere extends up to 1000 km from Earth’s surface and is divided into five layers:
- Troposphere: Extends approximately 13 km in altitude, with varying thickness (16 km at the equator, 7.8 km at the poles). Contains water vapor and is where most weather phenomena occur. Temperature decreases 6.5°C per 1000 m. The tropopause marks the transition to the stratosphere and is associated with the jet stream.
- Stratosphere: Extends from 13 km to 50 km in altitude. Temperature ranges from -40°C to -3°C. Contains the ozone layer, which absorbs UV radiation and heats the air.
- Mesosphere: Extends from 50 km to 85 km in altitude. Temperature decreases with altitude, reaching a minimum of -90°C at a pressure of 1 hPa.
- Thermosphere: Extends from 85 km to 500 km in altitude. Temperature increases with altitude due to absorption of solar radiation by O2 molecules.
- Exosphere: Extends from 500 km to 1000 km in altitude. Transition zone between Earth’s atmosphere and interplanetary space. Contains polar-orbiting satellites. Temperature and density are negligible.
Ionosphere
A region within the atmosphere with a high concentration of electrons and ions, formed by the effect of solar radiation. Extends from 60 km to 500 km in altitude and is divided into three layers (D, E, and F).
Atmospheric Variables
The most important atmospheric variables are temperature, density, pressure, and water vapor content. Less important variables include clouds, precipitation, and winds.
Weather vs. Climate
Weather refers to the atmospheric conditions at a given moment and place. Climate is the accumulation of daily and seasonal weather elements over time in a specific region.
Atmospheric Pressure
Pressure is the force per unit area, or the weight of air per unit surface area. It decreases with altitude at a rate of 1 hPa per 9 meters.
Measurement and Units
Pressure has been measured since the 17th century. Units of pressure include physical atmospheres (atm), pascals (Pa), hectopascals (hPa), and millibars (mb). 1 atm = 101,325 Pa = 1013 hPa = 1013 mb.
Key Concepts
- Barometric Tide: Regular daily changes in pressure.
- Barometric Trend: Pressure variation between two points.
- Isobars: Lines connecting points of equal pressure.
- Isalobars: Lines connecting points of equal barometric trend.
- Isohypses: Lines connecting points of equal geopotential altitude.
Isobaric Forms
Isobars on a surface map represent different pressure configurations. Main forms include anticyclones and depressions. Secondary forms include ridges, troughs, cols, and saddles.
Altitude Maps
Different pressure levels correspond to different altitudes (e.g., 850 hPa – 1500 m, 700 hPa – 3000 m).
Temperature
Temperature is a physical property representing the degree of heat. It is a measurable quantity related to the internal energy of bodies.
Heat Transfer
Heat can be transferred through conduction, convection, advection, radiation, and turbulent transfer.
General Circulation
The general circulation of the atmosphere is a balancing mechanism that counteracts the uneven distribution of solar radiation.
Humidity
Humidity refers to the water vapor content in the atmosphere. Key concepts include vapor pressure, saturation vapor pressure, and latent heat of vaporization.
Humidity Indices
Indices of humidity include absolute humidity and relative humidity.
Dew Point
The dew point is the temperature at which an air mass becomes saturated.