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YSU Vertical Dispersion Process Documentation

Overview

Yonsei University (YSU) planetary boundary layer vertical dispersion scheme for atmospheric transport, implementing scale-aware mixing with enhanced turbulence parameterization.

Process Type: transport Author: CATChem Development Team Version: 1.0 Date: 2025

Features

Available Schemes

  • scaleAwareYSU: Modern scale-aware YSU implementation with:
  • Enhanced entrainment calculations
  • Scale-aware mixing coefficients
  • Improved turbulence parameterization
  • CATChem constants integration
  • Modern diagnostic capabilities

Physical Features

  • Scale-aware mixing: Accounts for grid resolution effects on turbulent mixing
  • Enhanced entrainment: Improved boundary layer top entrainment calculations
  • Robust numerics: CFL-stable integration with modern error handling
  • Comprehensive diagnostics: Full suite of boundary layer diagnostics

Usage

Initialization

use ysuverticaldispersionProcess_Mod
type(ysuverticaldispersionProcessType) :: process
type(StateContainerType) :: container
integer :: rc

! Initialize the process
call process%init(container, rc)

Running the Process

! Run the process
call process%run(container, rc)

Finalization

! Clean up
call process%finalize(rc)

Configuration

The YSU vertical dispersion process requires meteorological data and boundary layer parameters.

Required Meteorological Fields

  • temperature: Air temperature [K]
  • potential_temperature: Potential temperature [K]
  • pressure: Air pressure [Pa]
  • air_density: Air density [kg/m³]
  • wind_u: Zonal wind component [m/s]
  • wind_v: Meridional wind component [m/s]
  • boundary_layer_height: Planetary boundary layer height [m]
  • surface_heat_flux: Surface sensible heat flux [W/m²]
  • friction_velocity: Surface friction velocity [m/s]

Available Diagnostics

  • mixing_coefficients: Vertical mixing coefficients [m²/s]
  • entrainment_rate: Entrainment rate at PBL top [m/s]
  • boundary_layer_height: Diagnosed PBL height [m]
  • mixing_length: Turbulent mixing length scale [m]
  • richardson_number: Bulk Richardson number [dimensionless]
  • stability_parameter: Atmospheric stability parameter [dimensionless]

Physical Parameterization

YSU Scheme Overview

The YSU scheme parameterizes vertical turbulent transport in the planetary boundary layer using:

  1. Mixing Length Formulation: Height-dependent mixing length with entrainment effects
  2. Stability Functions: Richardson number-based stability corrections
  3. Entrainment Parameterization: Enhanced entrainment at the boundary layer top
  4. Scale Awareness: Grid-resolution dependent mixing coefficients

Key Equations

Mixing Coefficient

K_h = κ * u* * h * φ_h(z/h) * (1 - z/h)²

Where: - κ = von Kármán constant (0.4) - u* = friction velocity [m/s] - h = boundary layer height [m] - φ_h = stability function for heat - z = height above surface [m]

Entrainment Rate

w_e = A * u*³ / (h * g * ∂θ_v/∂z)

Where: - A = entrainment efficiency coefficient - g = gravitational acceleration [m/s²] - ∂θ_v/∂z = virtual potential temperature gradient at PBL top [K/m]

Implementation Details

Process Structure

src/process/ysuverticaldispersion/
├── ysuverticaldispersionProcess_Mod.F90     # Main process module
├── ysuverticaldispersionCommon_Mod.F90      # Common utilities
└── schemes/                               # Scheme implementations
    ├── standardYSUScheme_Mod.F90
    ├── enhancedYSUScheme_Mod.F90
    ├── scaleAwareYSUScheme_Mod.F90

Testing

Unit tests are available in: 

tests/process/ysuverticaldispersion/
└── test_ysuverticaldispersion_process.F90

Run tests with: 

ctest -R ysuverticaldispersion

References