Update the dissipation length-scale

INTERFACE:

 
   subroutine do_lengthscale(nlev,dt,depth,u_taus,u_taub, z0s,z0b,h,NN,SS)

DESCRIPTION:

Based on the value of len_scale_method, this routine calls the appropriate routines for calculating the turbulent length-scale, $l$, and the rate of dissipation, $\epsilon$. The user has the choice between several algebraic equations described in section 4.19, and several differential transport equations for a length-scale determining variable. At the moment, GOTM implements equations for the rate of dissipation, described in section 4.15, for the Mellor-Yamada model described in section 4.14, and for the generic scale formulated by Umlauf and Burchard (2003) and described in section 4.16. This last transport equation generalises all of the previously mentioned models. For example, the $k$-$\epsilon$ model and the $k$-$\omega$ model can be recovered as special cases of the generic equation, see Umlauf and Burchard (2003).

USES:

   IMPLICIT NONE

INPUT PARAMETERS:

   integer,  intent(in)                :: nlev
   REALTYPE, intent(in)                :: dt,depth,u_taus,u_taub,z0s,z0b
   REALTYPE, intent(in)                :: h(0:nlev)
   REALTYPE, intent(in)                :: NN(0:nlev),SS(0:nlev)

REVISION HISTORY:

   Original author(s): Karsten Bolding, Hans Burchard,
                       Manuel Ruiz Villarreal,
                       Lars Umlauf