Update turbulence production


   subroutine production(nlev,NN,SS,xP)

This subroutine calculates the production terms of turbulent kinetic energy as defined in (154) and the production of buoayancy variance as defined in (161). The shear-production is computed according to

$\displaystyle P = \nu_t (M^2 + \alpha_w N^2) + X_P \; , \quad$ (148)

with the turbulent diffusivity of momentum, $ \nu_t$, defined in (46). The shear-frequency, $ M$, is discretised as described in section 3.13. The term multiplied by $ \alpha_w$ traces back to a parameterisation of breaking internal waves suggested by Mellor (1989). $ X_P$ is an extra production term, connected for example with turbulence production caused by sea-grass, see (274) in section 10.1. xP is an optional argument in the FORTRAN code.

Similarly, according to (80), the buoyancy production is computed from the expression

$\displaystyle G=-\nu^B_t N^2 + \tilde{\Gamma}_B \; , \quad$ (149)

with the turbulent diffusivity, $ \nu^B_t$, defined in (46). The second term in (149) represents the non-local buoyancy flux. The buoyancy-frequency, $ N$, is discretised as described in section 3.14.

The production of buoyancy variance by vertical meanflow gradients follows from (80) and (149)

$\displaystyle P_b = -G N^2 \quad .$ (150)

Thus, according to the definition of the potential energy (52), the buoyancy production $ G$ describes the conversion between turbulent kinetic and potential energy in (152) and (160), respectively.


   use turbulence, only: P,B,Pb
   use turbulence, only: num,nuh
   use turbulence, only: alpha,iw_model
   number of vertical layers
   integer,  intent(in)                :: nlev
   boyancy frequency squared (1/s^2)
   REALTYPE, intent(in)                :: NN(0:nlev)
   shear-frequency squared (1/s^2)
   REALTYPE, intent(in)                :: SS(0:nlev)
   TKE production due to seagrass
   friction (m^2/s^3)
   REALTYPE, intent(in), optional      :: xP(0:nlev)
   Original author(s): Karsten Bolding, Hans Burchard

Karsten Bolding 2012-12-28