Setup
for a new simulation to focus only on quasinighttime
conditions:
We
decided to start the simulation at 1000 UTC. At this time, the
lowlevel jet has not developed yet and the turbulence is already
much smaller.
As shown in the figure, evol_ws_0_40.gif,
1000 UTC (which corresponds at the 10 hour of run) corresponds to a
minimum in the mean wind speed averaged over the first 40 m. It
corresponds also to a minimum in the turbulent kinetic energy as
shown in the figure evol_tke_0_40m.gif
The
idea is to explore the 12 hours after this time.
As the
turbulence are going to be very shallow, this permits us to use a
much thinner domain (500m wide, 150m thick). Some preliminary work
(notably by B Maronga) seems to indicate that it is
better to use
an isotropic grid. So we propose for the LES a resolution as
*Dx=Dy=Dz=1m*.
As no radiosounding data is available at this
time, we propose to use the average of 3 LES using a zo=103
(the MesoNH, the PALM and the JPL simulations).
You can find the
initial profiles in the following netcdf file.
Please still
use the Stage 3 setup information for the rest (roughness lengths,
forcings...).
Total
information:

Domain: 500mx500mx150m
 Resolution : 1mx1mx1m
 Initial
profiles (th, u, v) : GABLS4_SCM_LES_STAGE3_10h.nc

radiation: no
 roughness length: zom=103; zoh=104
 surface
conditions: prescribed surface temperature (but be careful that
the
simulation will start at 1000 UTC, you can use the time
evolution of Ts in GABLS4_SCM_LES_STAGE3_10h.nc)
 boundary
conditions: cyclic
 top: you can add a dumping layer above 120m

largescale forcing: geostrophic wind constant in time, no advection
in T
To be able to disentangle the impact of flux formulation
and turbulence scheme
in the large spread of results of sensible
heat fluxes, we propose that each
center runs its simulation with
the default formulation of flux computation
and another simulation
that can be seen as a sensitivity test where we ask to
use the
following formulation for flux computation:
Proposed
flux formulation inspired by the flux formulation of
GABLS1:
Z_Z0_O_Z0H
= 10.0 ! the ratio between roughness length for momentum and
heat
ZBM=4.8 ! constant used in the formulation
ZBH=7.8 !
constant used in the formulation
ZL(:)=9999! initialization of
the MoninObukhov lengthscale
XKARMAN=0.4 ! VonKarman
constant
XP00=1.E5 ! reference
pressure
XCPD=7.*XRD/2.
XRD/XCPD=2./7.
XTG= surface
temperature
PPS: surface pressure
PTA: temperature of the 1st
level
PPA: pressure of the 1st level
PU: zonal wind of the 1st
level
PV: meridional wind of the 1st level
PRHOA= density of
the 1st level
ZVMOD= WIND_THRESHOLD(SQRT(PU(:)**2. +
PV(:)**2.),ZREF)
!routine to avoid a null modulus of wind (cf
below)
DO ZI=1,50 ! iteration over 50 times
!
computation of u*
ZUSTAR(:) = ZVMOD(:)/(LOG(ZREF(:)/Z0)/XKARMAN &
+ZBM/(ZL(:)*XKARMAN)*(ZREF(:)Z0))
!
computation of T*
ZTSTAR(:) =
(PTA(:)*((XP00/PPA)**(XRD/XCPD))XTG(:,1,1)*((XP00/PPS)**(XRD/XCPD)))
&
&
/(LOG(PZREF(:)/Z0/Z_Z0_O_Z0H)/XKARMAN+ZBH/(ZL(:)*XKARMAN)* &
&
(ZREF(:)Z0/Z_Z0_O_Z0H))
WHERE(ABS(ZTSTAR)<1.E10)
ZTSTAR(:) = 1.E10
END WHERE
WHERE(ABS(ZUSTAR)<1.E10)
ZUSTAR(:) = 1.E10
END
WHERE
ZL(:)=(ZUSTAR(:)**2)/(XG/(PTA(:)*((XP00/PPA)**(XRD/XCPD)))*XKARMAN*ZTSTAR(:))
END
DO
PSFU(:) =
PU(:)/ZVMOD(:)*(ZUSTAR(:)**2)*PRHOA
PSFV(:) =
PV(:)/ZVMOD(:)*(ZUSTAR(:)**2)*PRHOA
PSFTH(:) =
ZTSTAR(:)*ZUSTAR(:)*PRHOA*XCPD

Wind_threshold:
= = =
= = = = =
;determine a threshold for the wind
modulus
_
Wind_threshold(Pwind,Zref)
result(Pwind_new)
Pwind_new=max(Pwind,0.1*min(10.,Zref))