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Common Community Physics Package Developed at DTC
 
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GFS Scale-aware TKE-based Moist Eddy-Diffusion Mass-Flux (EDMF) PBL and Free Atmospheric Turbulence Scheme

Description

The current operational GFS scale-aware TKE-EDMF PBL scheme is an extended version of GFS Hybrid Eddy-Diffusivity Mass-Flux PBL and Free Atmospheric Turbulence scheme (Han et al. 2016 [79]; Han et al. 2017 [80]) with below enhancement:

  1. Eddy diffusivity (K) is now a function of TKE which is prognostically predicted
  2. EDMF approach is applied for all the unstable PBL
  3. EDMF approach is also applied to the stratocumulus-top-driven turbulence mixing
  4. It includes a moist-adiabatic process when updraft thermal becomes saturated
  5. Scale-aware capability
  6. It includes interaction between TKE and cumulus convection

The CCPP-compliant subroutine satmedmfvdifq_run() computes subgrid vertical turbulence mixing using scale-aware TKE-based moist eddy-diffusion mass-flux paramterization (Han et al. 2019 [76])

  • For the convective boundary layer, the scheme adopts EDMF parameterization (Siebesma et al. (2007)[180]) to take into account nonlocal transport by large eddies(mfpbltq.f)
  • A new mass-flux paramterization for stratocumulus-top-induced turbulence mixing has been introduced (mfscuq.f; previously, it was an eddy diffusion form)
  • For local turbulence mixing, a TKE closure model is used.
  • Wind shear effect in characteristic mixing length calculation is included, which reduces the mixing length in a strong shear environment such as a hurricane.
  • To better predict surface inversion as well as capping inversion near the PBL top, background diffusivity in the inversion layers is reduced as a function of surface roughness and green vegetation fraction.
  • To reduce the PBL overgrowth, the PBL updraft overshoot is not only limited by bulk Richardson number-based PBL depth, but the virtual potential temperature at the top of the surface layer rather than that at the model first layer is also used as the near-surface virtual potential temperature in the bulk-Richardson number computation. This helps to largely suppress the unrealistic widespread popcorn-like precipitation.
  • Updraft entrainment rates for moisture, hydrometeors, and tracers are increased by about 30%.
  • A positive definite total variation diminishing (TVD) mass-flux transport scheme for moisture, hydrometeors, and tracers and a method for removing negative tracer mixing ratio values have been implemented.
See also
NCEP Office Note 505 [84] and 506 [https://doi.org/10.25923/5051-3r70]

Intraphysics Communication

General Algorithm