Electromagnetic waves are the foundation of energy transfer in our atmosphere. From radio waves to gamma rays, these waves vary in wavelength, frequency, and energy, all traveling at the speed of light. Understanding their characteristics is crucial for grasping atmospheric processes.

The electromagnetic spectrum affects Earth's climate in various ways. Solar radiation, modified by factors like orbital variations and atmospheric absorption, drives our weather patterns. Meanwhile, infrared radiation plays a key role in the greenhouse effect, influencing global temperatures.

Electromagnetic Spectrum Characteristics and Components

Components of electromagnetic spectrum

• Electromagnetic spectrum range of all possible frequencies and wavelengths of electromagnetic radiation
• Extends from low frequency, long wavelength radio waves to high frequency, short wavelength gamma rays (radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays)
• All electromagnetic waves travel at speed of light in vacuum ($c = 3 \times 10^8$ m/s)

Wavelength, frequency, and energy relationships

• Wavelength ($\lambda$) distance between two consecutive crests or troughs of wave
  • Measured in meters (m) or submultiples (nm, μm)
• Frequency ($f$) number of wave cycles that pass fixed point per unit time
  • Measured in Hertz (Hz), cycles per second
• Energy ($E$) amount of energy carried by photon of electromagnetic radiation
  • Measured in Joules (J) or electron volts (eV)
• Relationship between wavelength, frequency, and speed of light: $c = \lambda f$
• Energy inversely proportional to wavelength and directly proportional to frequency: $E = h f = \frac{hc}{\lambda}$
  • $h$ is Planck's constant ($6.626 \times 10^{-34}$ J⋅s)
  • Higher frequency (shorter wavelength) radiation has higher energy, lower frequency (longer wavelength) has lower energy (X-rays vs radio waves)

Regions of electromagnetic spectrum

• Ultraviolet (UV) radiation
  • Wavelengths shorter than visible light (10-400 nm)
  • Divided into UV-A, UV-B, and UV-C
  • UV-C and most UV-B absorbed by ozone layer in stratosphere, UV-A and some UV-B reach Earth's surface causing sunburn and skin damage
• Visible light
  • Wavelengths between 400-700 nm
  • Comprises colors of rainbow (ROYGBIV)
  • Most solar radiation reaching Earth's surface in visible range
• Infrared (IR) radiation
  • Wavelengths longer than visible light (700 nm - 1 mm)
  • Divided into near-IR, mid-IR, and far-IR
  • Plays crucial role in Earth's energy balance and greenhouse effect, Earth's surface and atmosphere emit IR radiation

Factors affecting solar radiation

• Solar constant: average amount of solar radiation reaching top of Earth's atmosphere ($\approx 1361$ W/m²)
• Earth's orbital variations (Milankovitch cycles)
  1. Eccentricity: shape of Earth's orbit around Sun (100,000-year cycle)
  2. Axial tilt (obliquity): angle between Earth's rotational axis and perpendicular to orbital plane (41,000-year cycle)
  3. Precession: wobble of Earth's rotational axis (23,000-year cycle)
• Atmospheric absorption and scattering
  • Gases (ozone, water vapor, carbon dioxide) absorb radiation at specific wavelengths
  • Aerosols and molecules scatter radiation (Rayleigh and Mie scattering)
• Earth's surface albedo
  • Ratio of reflected to incident solar radiation
  • Varies with surface type (snow, ice, water, vegetation)
• Latitude and season
  • Higher solar radiation intensity at lower latitudes and during summer due to more direct angle of incidence