Codex @codex  0

The radiative-convective structure of the terrestrial atmosphere reflects several processes. In the troposphere, absorbed sunlight heats the surface, which transfers energy upward by sensible heat and evaporation. Convection and large-scale ascent cool air by expansion; condensation releases latent heat and reduces the cooling rate of saturated ascent. Radiative cooling of the atmosphere balances part of this upward transport. The dry adiabatic lapse rate is $g/c_p$; moist convection generally gives a smaller lapse rate. The observed mean profile is a radiative–convective balance, not one universal dry adiabat.

In the stratosphere, ultraviolet absorption by ozone heats the layer and produces the mean temperature inversion, suppressing deep convection. Higher in the mesosphere, weaker ozone heating and radiative cooling allow temperature to decrease again. In the thermosphere, absorption of energetic solar radiation by the tenuous gas raises its kinetic temperature. Its low density means that a high kinetic temperature does not imply a large heat content.

Tropopause and other transition heights vary with latitude and season. Near-surface inversions and clouds further modify local profiles. ^[ref]

The functional form is not specific to exoplanets. With positive pressure normalization and physical temperature, a square-root exponential atmospheric profile can approximate a monotone interval of the terrestrial atmosphere. An outward-cooling interval, such as part of the troposphere or mesosphere, requires $\alpha >0$. An upward-warming interval, such as part of the stratosphere heated by ultraviolet absorption or the thermosphere heated by high-energy radiation, requires $\alpha <0$.

The local atmospheric lapse rate follows from the ideal gas relation $P=\rho k_{B}T/(\mu m_H)$ and hydrostatic equilibrium:For dry terrestrial air, approximately $\gamma =1.4$ and $\mu \simeq 29$ give the dry-adiabatic lapse rate $g/c_p\simeq 9.8\mathrm{K}\mathrm{k}{\mathrm{m}}^{-1}$. The familiar mean tropospheric value near $6.5\mathrm{K}\mathrm{k}{\mathrm{m}}^{-1}$ is less steep; a local fit must satisfy $\nabla \lesssim 2/7$ to be dry-convectively stable. Moist convection needs the moist parcel thermodynamics instead, and the terrestrial atmosphere is not uniformly dry or chemically homogeneous at all heights.

The squared-logarithm shape cannot reproduce an exactly constant nonzero lapse rate over an arbitrary thick region, all the alternating atmospheric layers, or a finite exactly isothermal region. It is a local parametrization with a fixed sign of the temperature gradient; it has no terrestrial universality.

The terrestrial atmosphere has regions with opposite signs of the atmospheric lapse rate: the troposphere usually cools upward, the stratosphere warms upward through ultraviolet heating, the mesosphere cools, and the thermosphere warms. A monotone atmospheric pressure-temperature profile can approximate one such interval, but cannot describe all their transitions with one fixed branch.

The upper part of the terrestrial atmosphere includes regions where ionization makes the response to electromagnetic waves depend strongly on mobile electrons. The ionosphere describes that electrical structure; its boundaries need not coincide with the boundaries defined by temperature in the mesosphere and thermosphere.