Cloud_physics

Aerosol scavenging by cloud droplets (Seinfeld & Pandis 2006, Eqs. 17.84-17.92). Computes mass and number scavenging ratios and the scavenging coefficient for a monodisperse cloud-droplet population.

Adiabatic cooling and cloud-base thermodynamics — Seinfeld & Pandis (2006), Ch. 17. Computes five purely-algebraic quantities that characterize when and where a lifted air parcel reaches its lifting condensation level (LCL): the dry adiabatic lapse rate Γ_d, the saturation vapor pressure p_sat (Magnus formula), the saturation mixing ratio w_vs, the dew-point temperature T_d (Eq. 17.43), and the LCL height h_LCL (Eq. 17.49). Migrated from Aerosol.jl CloudDynamics.

Kelvin effect on the equilibrium vapor pressure over a curved cloud droplet surface — Seinfeld & Pandis (2006), Ch. 17. Computes the Kelvin length parameter A_K = 4 σ_w M_w / (R T ρ_w) and the Kelvin saturation ratio S_K = exp(A_K / D_p), the factor by which surface curvature enhances equilibrium vapor pressure over a small droplet relative to a flat surface. Used as the curvature term in the Köhler equation (Eq. 17.27). Migrated from Aerosol.jl CloudKelvinEffect.

Composed cloud microphysics model (Seinfeld & Pandis 2006, Ch. 17). Flat composition of CloudDynamics (adiabatic thermodynamics, LCL height), IcePhysics (freezing point depression, ice nuclei), RainFormation (collision-coalescence, raindrop spectra), and AerosolScavenging (scavenging ratios and coefficient). Shared physical constants M_w and R unify CloudDynamics and IcePhysics. Ice particle diameter (D_p_ice) and collector drop diameter (D_p_rain) are kept as independent parameters. Migrated from Aerosol.jl src/cloud_physics.jl:735 (esm-c8z).

Thermodynamic properties of water and aqueous solutions for cloud-physics calculations: temperature offset, specific heat of liquid water, latent heats of vaporization and melting, surface tension, and saturation vapor pressure over water and ice. Based on Seinfeld & Pandis (2006), Chapter 17, Equations 17.1–17.6 and Table 17.2. Migrated from Aerosol.jl src/cloud_physics.jl:15.

Diffusional growth rate of a cloud droplet by condensation of water vapor. Accounts for vapor-phase diffusion (D_v), the kinetic correction to the diffusivity (D_v'), thermal conductivity of air (k_a and k_a'), and the curvature + solute (Köhler) contributions to the equilibrium saturation ratio S_eq over the droplet surface. Output is the droplet-diameter growth rate dD_p/dt (m/s) from Seinfeld & Pandis (2006) Eq. 17.70. Source: Aerosol.jl@c8c640bb src/cloud_physics.jl:322 (mtk2esm-scaffolded, mdl-43a).

Ice nucleation and ice-water equilibrium thermodynamics (Seinfeld & Pandis 2006, Eqs. 17.100-17.103). Computes freezing point depression for solutions, equilibrium freezing temperature from water activity, Kelvin curvature factor for ice particles, and empirical ice-nuclei concentration.

Köhler theory for cloud condensation nucleus (CCN) activation — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., §17.3–17.4. Computes the equilibrium saturation ratio S_eq over a solution droplet of diameter D_p (Köhler equation, Eq. 17.50), the critical activation diameter D_pc, and the critical supersaturation sc. S_eq combines the Kelvin curvature enhancement (coefficient A = 4 M_w σ / (R T ρ_w)) and the Raoult solute suppression (coefficient B = 6 n_s M_w / (π ρ_w)); at D_p = D_pc the Köhler curve reaches its maximum and the droplet activates spontaneously. Migrated from Aerosol.jl src/cloud_physics.jl:232.

Rain formation by collision and coalescence (Seinfeld & Pandis 2006, Eqs. 17.104-17.108). Computes collection efficiency, continuous accretion rate, and raindrop size distributions (Best CDF and Marshall-Palmer number density).