Atmospheric Physics

• Photodissociation:

  • Process of dissociating oxygen molecules (O2) to individual element (O) in the atmosphere and joins them to form ozone with the help of light energy
• Ozone (O3):

  • Molecule formed about 30 km from the surface
  • In the atmosphere it prevents the entry of harmful radiations while on the surface, it suffocates human
• Water vapor:

  • Contains from 0-4% in the atmosphere
  • It forms a cloud during condensation and falling back to the surface as precipitation
  • Acts as a source of thermal energy in the atmosphere, in relation to the intensive heat transfer between the Earth’s surface and the atmosphere, as a result, it initiated weather disturbances
• Troposphere:

  • 8-20 km above surface
  • 75% of the mass of the atmosphere
• Stratosphere:

  • Isothermal layer (first 10 km)
  • First temperature inversion
• Mesosphere:

  • 50-80 km above surface
  • Mesopause (-84 °C)
• Thermosphere:

  • Hottest layer (heterosphere)
  • Temperature inversion
  • No thermopause
• The height of the atmosphere can be measured based on specific phenomena like duration of dawn and twilight, observation of shooting stars, and aurora borealis and aurora australis
• The mass of the atmosphere can be assessed using pressure formula with given calculations showing the percent total mass of the atmosphere at different heights
• Photodissociation:

  • Process of dissociating oxygen molecules (O2) to individual element (O) in the atmosphere and joins them to form ozone with the help of light energy
• Ozone (O3):

  • Molecule formed about 30 km from the surface
  • In the atmosphere it prevents the entry of harmful radiations while on the surface, it suffocates human
• Water vapor:

  • Contains from 0-4% in the atmosphere
  • It forms a cloud during condensation and falling back to the surface as precipitation
  • Acts as a source of thermal energy in the atmosphere, in relation to the intensive heat transfer between the Earth’s surface and the atmosphere, as a result, it initiated weather disturbances
• Troposphere:

  • 8-20 km above surface
  • 75% of the mass of the atmosphere
• Stratosphere:

  • Isothermal layer (first 10 km)
  • First temperature inversion
• Mesosphere:

  • 50-80 km above surface
  • Mesopause (-84 °C)
• Thermosphere:

  • Hottest layer (heterosphere)
  • Temperature inversion
  • No thermopause
• The height of the atmosphere can be measured based on specific phenomena like duration of dawn and twilight, observation of shooting stars, and aurora borealis and aurora australis
• The mass of the atmosphere can be assessed using pressure formula with given calculations showing the percent total mass of the atmosphere at different heights
• Evolution of the atmosphere:

  • Primordial atmosphere: Atmosphere made from the origin material in a protoplanetary disk and retain since the formation of a planet. Gas giants such as Jupiter and Saturn have primordial atmospheres.
  • Secondary atmosphere: Atmosphere produced by outgassing of volatile compounds from the rocky material of a terrestrial-type planet. Venus, Earth, and Mars, for example, possess secondary atmospheres
• Hydrostatic Balance Equation:

  • The formation of a layer of atmosphere implies that this layer is in a state of equilibrium
  • Atmospheric pressure is the force per unit area exerted on a surface by the weight of the air above
  • Hydrostatic equilibrium exists if the force due to gravity is balanced by the vertical pressure gradient force
• Equation of the State:

  • Molecules inside a system move randomly in all directions in Brownian motion
  • Avogadro’s number: Number of units in one mole of any substance
  • Ideal Gas Law: pV = mRT, where p, V, m, and T are pressure, volume, mass, and absolute temperature respectively, and R is a constant (gas constant) for a 1 kg of gas
• Troposphere - The lowest layer of the atmosphere where most weather occurs, extending from the surface to an altitude of approximately 16 km at the poles and up to 20 km near the equator.
• Atmospheric pressure at sea level is approximately 1013 hPa or 1 atm.
• The mesosphere is a layer of the atmosphere located above the stratosphere.
• The atmosphere is the gaseous envelope surrounding Earth, consisting mainly of nitrogen (78%), oxygen (21%), and trace amounts of other gases.
• Radiation is a form of energy represented by particles or waves traveling through a medium or space
• Two distinct types of radiation: Ionizing (having sufficient energy to ionize an atom) and Non-ionizing (e.g., radio waves, heat or infrared, visible light, etc.)
• All objects emit radiation (Stefan-Boltzmann)
• Particles or waves radiate isotropically from a source
• EMR is a form of energy exhibiting wave-like behavior as it travels through space
• Photon is the quantum of the electromagnetic interaction and the basic unit of light and all other forms of radiation
• EMR carries energy (radiant energy) and momentum that may be imparted to matter through absorption of EMR
• Terms to know:

  • Speed of light (c) = 2.998 x 10^8 m/s
  • Wavelength (λ) – distance from one wave crest to the next
  • Frequency (ν) – number of waves per unit time (unit: Hertz; Hz)
  • Wave number (σ or n) – number of waves per unit length (1/λ; unit: cycles m^-1)
  • Circular or Angular frequency (ω) - 2πν
  • Solid angle (Ω)
• Radio waves used by active radio sensors

  • Microwaves mostly used by microwave radiometers/spectrometers and radar system
  • Infrared used in remote sensing with molecular rotation and vibration playing important roles
  • Visible light with electronic energy levels playing a key role in wave-matter interaction
  • Ultraviolet with electronic energy levels playing the main role in wave-matter interaction
  • X-ray and Gamma rays used to study planetary atmospheres or surfaces with no atmosphere
• Blackbodies do not reflect or scatter radiation but absorb and re-emit it completely

  • Radiation of a blackbody depends only on its temperature
  • Planck’s Law explains the wavelength distribution of the radiation
  • Wein’s Displacement Law determines the maximum wavelength emitted by a blackbody
  • Stefan-Boltzmann Law relates total energy emitted to absolute temperature
• Intensity and Flux density:

  • Monochromatic Intensity is the energy transferred by EMR in a specific direction passing through an area per unit time at a specific wavelength
  • Radiance is the integral of monochromatic intensity over some finite range of the electromagnetic spectrum
  • Monochromatic flux density is the rate of energy per unit area by radiation with a given wavelength through a plane surface with a specified orientation in three-dimensional plane
• Atmospheric windows:

  • Radiative energy is partly absorbed by different molecules in the atmosphere
  • Atmospheric transmission windows include visible and reflected infrared region, thermal infrared region, and microwave region
• Greenhouse effect:

  • Earth’s equilibrium temperature is 255 K (-18 °C)
  • Computed surface temperature is 288 K (15 °C) due to absorption of terrestrial radiation
  • Greenhouse effect traps most of the terrestrial radiation inside the Earth’s atmosphere
  • Earth’s surface temperature is higher due to the presence of an atmosphere
• Heat Transfer:

  • Heat is energy transfer caused by a temperature difference
  • Internal energy is the sum of mechanical energies of molecules and is proportional to temperature
  • Heat transfer occurs through conduction, convection, and radiation
• Conduction is heat transfer through stationary matter by physical contact

  • Convection is heat transfer by the macroscopic movement of a fluid
  • Radiation occurs when electromagnetic radiation is emitted or absorbed