116
Air Pollution and Turbulence: Modeling and Applications
prescription of constant latent and sensible heat fl uxes,
5
1
2.5 10 m s
s
w q
−
−
=
×
′ ′
and
2
1
6.10 K m s
s
w
−
−
θ =
′ ′
, respectively. The surface variables are θ s = 300 K, q s = 5 g kg −1
and p s = 1000 hPa. The initial profi les of potential temperature and humidity can be
summarized:
4
1
300 K,
3.7 10 km
0
1350 m
t
q t
z
−
−
θ =
∂ ∂ = − ×
< <
−
−
−
∂θ ∂ =
∂ ∂ = − ×
>
1
4
1
2 K km ,
9.4 10 km
1350 m
t
z
q t
z
Simulations were done with the one-dimensional version of MesoNH, where the
EDMF scheme was implemented. A constant vertical resolution of 20 m (as in the
LES simulations) and a 60 s time step were used.
In general, the results were better than those produced with the EDMF version
presented before. The results revealed a signifi cant improvement of the MesoNH
model with the EDMF closure, especially in what concerns the evolution of the top
inversion, but also in the vertical structure of the mixed layer. The EDMF scheme
showed improvements in BL features, associated with a closer agreement of the overall profi les. Most important is the fact that EDMF is capable of reproducing a slightly
stable upper mixed layer and a much better BL growth. The improvement of the representation of the average properties of the BL is, obviously, related to a better representation of the vertical fl uxes. The time evolution of the vertical fl uxes of potential
temperature (not shown) and total specifi c humidity (Figure 4.22) illustrates this
enhanced transport. In particular, the heat fl ux shows a realistic linear profi le with
a top-entrainment ratio min(
)/(
) s
w
w
θ
θ
′ ′
′ ′ of 0.17, on spot with LES results. In what
concerns the humidity fl uxes, there is again a clear improvement in the profi les,
associated with a better BL growth, but some discrepancies remain, and they are
responsible for the moister BL found in both 1D simulations.
In this version, the MF contribution for the potential temperature is enhanced.
Figure 4.23 shows the values of the ED and the MF terms contributing to the potential temperature vertical fl ux. It can be seen that the MF term gives the leading
3
2
1
0
0.0
2.0 × 10 –5
4.0 × 10 –5
w΄q΄ t (ms –1 )
Height (km)
4 h
8 h
LES
CBR
EDMF
FIGURE 4.22 Hourly averaged specifi c humidity fl ux profi les. Results from the EDMF
scheme, Cuxart et al. (2000) (CBR) scheme, and KNMI LES.
© 2010 by Taylor and Francis Group, LLC
Air Pollution and Turbulence: Modeling and Applications
prescription of constant latent and sensible heat fl uxes,
5
1
2.5 10 m s
s
w q
−
−
=
×
′ ′
and
2
1
6.10 K m s
s
w
−
−
θ =
′ ′
, respectively. The surface variables are θ s = 300 K, q s = 5 g kg −1
and p s = 1000 hPa. The initial profi les of potential temperature and humidity can be
summarized:
4
1
300 K,
3.7 10 km
0
1350 m
t
q t
z
−
−
θ =
∂ ∂ = − ×
< <
−
−
−
∂θ ∂ =
∂ ∂ = − ×
>
1
4
1
2 K km ,
9.4 10 km
1350 m
t
z
q t
z
Simulations were done with the one-dimensional version of MesoNH, where the
EDMF scheme was implemented. A constant vertical resolution of 20 m (as in the
LES simulations) and a 60 s time step were used.
In general, the results were better than those produced with the EDMF version
presented before. The results revealed a signifi cant improvement of the MesoNH
model with the EDMF closure, especially in what concerns the evolution of the top
inversion, but also in the vertical structure of the mixed layer. The EDMF scheme
showed improvements in BL features, associated with a closer agreement of the overall profi les. Most important is the fact that EDMF is capable of reproducing a slightly
stable upper mixed layer and a much better BL growth. The improvement of the representation of the average properties of the BL is, obviously, related to a better representation of the vertical fl uxes. The time evolution of the vertical fl uxes of potential
temperature (not shown) and total specifi c humidity (Figure 4.22) illustrates this
enhanced transport. In particular, the heat fl ux shows a realistic linear profi le with
a top-entrainment ratio min(
)/(
) s
w
w
θ
θ
′ ′
′ ′ of 0.17, on spot with LES results. In what
concerns the humidity fl uxes, there is again a clear improvement in the profi les,
associated with a better BL growth, but some discrepancies remain, and they are
responsible for the moister BL found in both 1D simulations.
In this version, the MF contribution for the potential temperature is enhanced.
Figure 4.23 shows the values of the ED and the MF terms contributing to the potential temperature vertical fl ux. It can be seen that the MF term gives the leading
3
2
1
0
0.0
2.0 × 10 –5
4.0 × 10 –5
w΄q΄ t (ms –1 )
Height (km)
4 h
8 h
LES
CBR
EDMF
FIGURE 4.22 Hourly averaged specifi c humidity fl ux profi les. Results from the EDMF
scheme, Cuxart et al. (2000) (CBR) scheme, and KNMI LES.
© 2010 by Taylor and Francis Group, LLC