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FENGSHA

Overview

Implements the FENGSHA dust emission scheme, a physically-based saltation model that computes size-resolved dust emissions using friction velocity, soil texture, moisture corrections, and drag partitioning. The scheme includes Fécan moisture correction, Marticorena & Bergametti (1995) vertical-to-horizontal flux ratio, and distributes emissions across multiple size bins using a Kok distribution.

References:

  • Fécan, F., et al. (1999), Annales Geophysicae, 17, 149–157.
  • Marticorena, B. and Bergametti, G. (1995), JGR, 100(D8), 16415–16430.
  • Webb, N.P., et al. (2020), Current Opinion in Environmental Sustainability, 44, 138–146.

Registration Names

  • Native C++: "fengsha"
  • Fortran bridge: "fengsha_fortran"

Configuration Parameters

YAML Key Type Default Description
alpha double 1.0 Sandblasting efficiency parameter
gamma double 1.0 Erodibility exponent for SSM
kvhmax double 2.45e-4 Maximum vertical-to-horizontal flux ratio
grav double 9.81 Gravitational acceleration [m/s²]
drylimit_factor double 1.0 Fécan dry-limit scaling factor
num_bins int 5 Number of dust size bins

Import Fields

Field Name Units Description
friction_velocity m/s Surface friction velocity (u*)
threshold_velocity m/s Threshold friction velocity
soil_moisture fraction Volumetric soil liquid water content
clay_fraction fraction Fractional clay content [0–1]
sand_fraction fraction Fractional sand content [0–1]
silt_fraction fraction Fractional silt content [0–1]
erodibility dimensionless Sediment supply map (SSM)
drag_partition dimensionless Drag partition correction factor
air_density kg/m³ Surface air density
lake_fraction fraction Lake fraction [0–1]
snow_fraction fraction Snow cover fraction [0–1]
land_mask dimensionless Land mask (1 = land)

Export Fields

Field Name Units Description
fengsha_dust_emissions kg/m²/s Size-resolved dust emission flux (3D: nx × ny × nbins)

Algorithm

  1. Skip non-land cells and cells with erodibility (SSM) below threshold (0.01).
  2. Compute land fraction accounting for lake and snow cover.
  3. Compute vertical-to-horizontal flux ratio (MB95): kvh = 10^(13.4*clay − 6) for clay < 0.2, capped at kvhmax.
  4. Compute total emission scaling: (alpha/grav) * fracland * SSM^gamma * air_density * kvh.
  5. Adjust friction velocity by drag partition: rustar = rdrag * u*.
  6. Convert volumetric to gravimetric soil moisture, then compute Fécan moisture correction factor H from clay content and dry limit.
  7. Adjust threshold: u_thresh = threshold_velocity * H.
  8. Compute horizontal saltation flux (Webb et al. 2020, Eq. 9): q = max(0, rustar − u_thresh) * (rustar + u_thresh)².
  9. Distribute across bins using hard-coded Kok distribution: [0.1, 0.25, 0.25, 0.25, 0.15].

YAML Configuration Example

physics:
  - name: fengsha
    config:
      alpha: 1.0
      gamma: 1.0
      kvhmax: 2.45e-4
      drylimit_factor: 1.0
      num_bins: 5

Implementation Notes

  • Available as both native C++ (Kokkos) and Fortran bridge implementations
  • Produces multi-bin (3D) output; the third dimension is the size bin index
  • The Kok bin distribution is hard-coded for up to 5 bins
  • Requires 12 import fields — the most input-intensive scheme alongside K14