Seinfeld_pandis_ch12

Characteristic timescale for aqueous-phase diffusion within a droplet — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12, Eq. 12.75. The aqueous-phase diffusion timescale τ_da = R_p²/(π²D_aq) is the characteristic time for a dissolved species to diffuse throughout the interior of a droplet of radius R_p with aqueous-phase diffusivity D_aq. It is the e-folding decay time of the fundamental (slowest) mode of the spherical diffusion equation, whose lowest eigenvalue contributes the π² factor. Migrated from Aerosol.jl AqueousDiffusionTimescale.

Characteristic timescale for a gas to equilibrate with aqueous aerosol particles — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12, Eq. 12.147. The aqueous equilibration timescale τ_a is the solid-particle equilibration timescale τ_s scaled by the dimensionless buffering factor m_w/K_A, where m_w is the aerosol water mass concentration and K_A is an equilibrium constant. The factor accounts for the additional buffering effect of Henry's-law dissolution of the gas into the aerosol aqueous phase: a larger aqueous reservoir m_w relative to K_A lengthens the time to reach equilibrium. Migrated from Aerosol.jl AqueousEquilibrationTimescale.

Characteristic timescale for gas-phase diffusion of a species to an aerosol particle — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12, Eq. 12.49. The gas-phase diffusion timescale τ_dg = R_p²/(4·D_g) is the characteristic time for a gas-phase concentration perturbation to diffuse to the surface of a particle of radius R_p, given the gas-phase molecular diffusivity D_g of the species. It is one of the family of mass-transfer timescales in Ch. 12 — gas-phase diffusion, interfacial transport, aqueous-phase diffusion, aqueous-phase reaction — that are compared against one another to identify the rate-limiting step in gas-to-particle conversion: a short τ_dg means gas-phase diffusion is fast and not the bottleneck. The timescale grows quadratically with the particle radius and inversely with the diffusivity. Migrated from Aerosol.jl GasDiffusionTimescale.

Characteristic timescale to achieve equilibrium at the gas-particle interface for a gas exchanging with an aqueous aerosol droplet — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12, Eqs. 12.61-12.62. Two limiting regimes are computed. For very soluble gases the approach to interfacial equilibrium is controlled by interfacial (accommodation-limited) mass transport, τ_p_soluble ≈ R_p·H*·√(2π·M_A·R·T)/(3α) (Eq. 12.61). For low-solubility gases it is instead controlled by aqueous-phase diffusion within the droplet interior, τ_p_insoluble ≈ R_p²/(π²·D_aq) (Eq. 12.62). Migrated from Aerosol.jl InterfacialTimescale.

ModelingToolkit implementation of the characteristic timescale for aqueous-phase chemical reaction within a cloud droplet or wetted aerosol particle, from Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12, Eqs. 12.76-12.78. The component reports two diagnostics for a first-order aqueous reaction: the aqueous-phase reaction timescale τ_ra = 1/k_rxn (Eq. 12.76), the e-folding time of a dissolved species consumed by a first-order reaction of rate constant k_rxn; and the gas-phase reference reaction timescale τ_rg = τ_ra/(H*·R·T) (Eq. 12.78), the same timescale referenced to the gas phase through the dimensionless effective Henry's law solubility H*·R·T. Migrated from Aerosol.jl ReactionTimescale. Purely algebraic: no differential states, two observed outputs and an empty equations array.

Characteristic timescale for a gas to equilibrate with solid aerosol particles — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 12. Computes the solid-particle gas-equilibration timescale in two equivalent forms: τ_s = ρ_p R_p²/(3 D_A m_p f) expressed via the aerosol mass concentration m_p (Eq. 12.135), and τ_s_alt = 1/(4π N R_p D_A f) expressed via the particle number concentration N and radius R_p (Eq. 12.139). The two forms coincide when the mass and number parameterizations are mutually consistent. Migrated from Aerosol.jl SolidEquilibrationTimescale.