# Changeset 40 for palm/trunk/DOC/app/chapter_4.1.html

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Timestamp:
Mar 2, 2007 6:32:25 AM (15 years ago)
Message:

documentation update for the new svn-based version and for 3.1c, update of .mrun.config.default, -u in mbuild only compiles scripts

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• ## palm/trunk/DOC/app/chapter_4.1.html

 r5

Allowed are the values 'dirichlet' (pt(k=nz) and pt(k=nz+1) do not change during the run) and 'neumann'. With the Neumann boundary condition the value of the temperature gradient at the top is (pt(k=nz+1) does not change during the run), 'neumann' (pt(k=nz+1)=pt(k=nz)), and 'initial_gradient'. With the 'initial_gradient'-condition the value of the temperature gradient at the top is calculated from the initial temperature profile (see pt_surface, pt_vertical_gradient) by bc_pt_t_val = (pt_init(k=nz) - pt_init(k=nz-1)) / dzu(nz).
by bc_pt_t_val = (pt_init(k=nz+1) - pt_init(k=nz)) / dzu(nz+1).

pt(k=nz) = pt(k=nz-1) + bc_pt_t_val * dzu(nz)

and

(up to k=nz-1 the prognostic equation for the temperature is solved).

(up to k=nz the prognostic equation for the temperature is solved).
When a constant sensible heat flux is used at the top boundary (top_heatflux), bc_pt_t = 'neumann' must be used, because otherwise the resolved scale may contribute to the top flux so that a constant value cannot be guaranteed.

q(k=nz) = q(k=nz-1) + bc_q_t_val * dzu(nz)

and

(up tp k=nz-1 the prognostic

(up tp k=nz the prognostic equation for q is solved).

s(k=nz) = s(k=nz-1) + bc_s_t_val * dzu(nz)

and

(up to k=nz-1 the prognostic

(up to k=nz the prognostic equation for the scalar concentration is solved).

logarithmic wind and temperature profiles between k=0 and k=1. In this case a Dirichlet condition (see bc_pt_b) must be used as bottom boundary condition for the potential temperature.

must be used as bottom boundary condition for the potential temperature.

top_heatfluxRno prescribed
heatflux

Kinematic sensible heat flux at the top boundary (in K m/s).

If a value is assigned to this parameter, the internal two-dimensional surface heat flux field tswst is initialized with the value of top_heatflux as top (horizontally homogeneous) boundary condition for the temperature equation. This additionally requires that a Neumann condition must be used for the potential temperature (see bc_pt_t), because otherwise the resolved scale may contribute to the top flux so that a constant value cannot be guaranteed.

Note:
The application of a top heat flux additionally requires the setting of initial parameter use_top_fluxes = .T..

No Prandtl-layer is available at the top boundary so far.