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Model Overview

Welcome to the Canopy-App atmospheric canopy modeling system comprehensive overview.

Introduction

Canopy-App is a sophisticated one-dimensional model designed to simulate atmospheric processes within and above forest canopies. It was developed to provide detailed representation of:

  • Canopy meteorology - Wind speed, temperature, and humidity profiles
  • Radiation transfer - Solar and longwave radiation attenuation
  • Biogenic emissions - Volatile organic compound (VOC) emissions from vegetation
  • Dry deposition - Removal of gases and particles by canopy surfaces
  • Photochemical processes - In-canopy photolysis rate calculations

Model Architecture

graph TD
    A[Input Data] --> B[Canopy-App Core]
    B --> C[Meteorology Module]
    B --> D[Radiation Module]
    B --> E[Biogenic Emissions Module]
    B --> F[Dry Deposition Module]
    B --> G[Photolysis Module]

    C --> H[Output Files]
    D --> H
    E --> H
    F --> H
    G --> H

    I[Configuration] --> B
    J[Physics Parameters] --> B

Key Components

1. Canopy Meteorology (canopy_canmet_mod)

  • Computes wind speed profiles using similarity theory
  • Calculates temperature and humidity gradients
  • Handles atmospheric stability corrections
  • Accounts for canopy drag and momentum absorption

Key Features: - Multi-layer canopy representation - Stability-dependent mixing lengths - Canopy influence on turbulence

2. Radiation Transfer (canopy_rad_mod)

  • Solar radiation attenuation through canopy layers
  • Longwave radiation exchange
  • Photosynthetically active radiation (PAR) calculations
  • Solar zenith angle computations

Key Features: - Beer's law attenuation with leaf area density - Direct and diffuse radiation components - Seasonal solar angle variations

3. Biogenic Emissions (canopy_bioemi_mod)

  • Temperature-dependent emission rates
  • Light-dependent emissions (isoprene)
  • Species-specific emission factors
  • Canopy-scale flux integration

Key Features: - MEGAN-like algorithms - Multiple chemical species - Environmental stress factors

4. Dry Deposition (canopy_drydep_mod)

  • Multi-layer resistance network
  • Stomatal and cuticular uptake
  • Species-specific deposition velocities
  • Environmental controls on deposition

Key Features: - Big-leaf and multi-layer approaches - Gaseous and particulate (future) deposition - Season and species dependencies

5. Photolysis Rates (canopy_phot_mod)

  • Attenuation of actinic flux
  • Species-specific photolysis rates
  • Canopy shading effects
  • Solar zenith angle dependencies

Key Features: - Wavelength-dependent calculations - Multiple photolysis reactions - Canopy optical properties

Model Domain

Vertical Structure

    ┌─────────────────┐  ← Above canopy (reference level)
    │                 │
    │   Canopy Top    │  ← z_cantop
    ├─────────────────┤
    │ ║ ║ ║ ║ ║ ║ ║ ║ │  ← Canopy layers (ncanlevs)
    │ ║ ║ ║ ║ ║ ║ ║ ║ │
    │ ║ ║ ║ ║ ║ ║ ║ ║ │
    │ ║ ║ ║ ║ ║ ║ ║ ║ │
    ├─────────────────┤
    │  Canopy Bottom  │  ← z_canbot
    └─────────────────┘  ← Ground level

Spatial Considerations

  • Horizontal: Point-based calculations (1D vertical column)
  • Vertical: User-configurable number of canopy layers
  • Temporal: Instantaneous calculations for given meteorological conditions

Input Requirements

Meteorological Data

  • Wind speed and direction
  • Air temperature
  • Relative humidity
  • Surface pressure
  • Solar radiation components
  • Precipitation (optional)

Canopy Parameters

  • Canopy height and structure
  • Leaf area index (LAI)
  • Plant functional type
  • Emission factors (species-specific)
  • Phenology information

Model Configuration

  • Physics options and switches
  • Numerical parameters
  • Output specifications
  • Quality control settings

Output Products

Standard Variables

  • Meteorology: Wind, temperature, humidity profiles
  • Radiation: Solar flux, PAR availability
  • Emissions: Biogenic VOC fluxes by species
  • Deposition: Dry deposition velocities and fluxes
  • Photolysis: J-values for chemical species

Output Formats

  • NetCDF: Structured, self-describing format
  • Text: Human-readable ASCII format
  • Point data: Time series at specific locations

Scientific Applications

Research Applications

  • Forest-atmosphere exchange studies
  • Air quality modeling input
  • Climate change impact assessment
  • Ecosystem-atmosphere coupling research

Operational Applications

  • Biogenic emission inventories
  • Air quality forecasting
  • Environmental impact assessment
  • Forest management planning

Model Strengths

✅ Physically-based: Implements well-established scientific algorithms ✅ Comprehensive: Covers multiple canopy processes in integrated framework ✅ Flexible: Configurable for different forest types and research needs ✅ Validated: Based on field measurements and inter-model comparisons ✅ Efficient: Optimized Fortran implementation for operational use ✅ Open Source: Freely available with complete documentation

Limitations

⚠️ Chemical Simplification: Limited in-canopy chemistry representation

Model Validation

The model has been validated against: - Flux tower measurements - Field campaign data - Other canopy models - Laboratory studies

Key Validation Studies: - Forest canopy wind profiles - Biogenic emission flux measurements

Next Steps