Changes between Version 394 and Version 395 of doc/app/initialization_parameters

Timestamp:

Jul 19, 2018 9:02:52 PM (7 years ago)

Author:

maronga

Comment:

--

doc/app/initialization_parameters

@@ -2053 +2053 @@
 
 Detailed information can be found in the documentation of the [../../tec/noncyclic non-cyclic lateral boundary conditions].
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
+[=#use_free_convection_scaling '''use_free_convection_scaling''']
+}}}
+{{{#!td style="vertical-align:top"
+L
+}}}
+{{{#!td style="vertical-align:top"
+.F.
+}}}
+{{{#!td
+Parameter to switch on the use of the local free convection velocity scale {{{w_lfc}}}.
+
+When switched on, {{{w_lfc}}} is added to the horizontal wind velocity for use in the constant flux layer parameterization to calculate the Obukhov length and the friction velocity {{{u_*}}} over horizontally-aligned surfaces. The horizontal velocity {{{u_h}}} at height of the first vertical grid level {{{z_mo}}} is then calculated as:
+{{{
+#!Latex
+$$u_\mathrm{h} = \left(u(z_\mathrm{mo})^2 + v(z_\mathrm{mo})^2 + w_\mathrm{lfc}^2\right)^{1/2}$$
+}}}
+with
+{{{
+#!Latex
+$$w_\mathrm{lfc} = \left( \frac{g}{\thetaz_\mathrm{mo})} * z_\mathrm{mo} * \overline{w'\theta'}_0\right)^{1/3}$$
+}}}
+This is particularly useful in simulations of convective boundary layers where the local near-surface wind is expected to close to zero, e.g. in urban environments when the present buildings create spots of stagnant air. {{{w_lfc}}} accounts for the dominant eddies close to the surface that cannot be resolved by the LES model and increases {{{u_h}}} by a small amount. When using the land surface scheme, this might prevent the surface sensible heat flux from dropping to zero under no-wind conditions.
 }}}
 |----------------