Fine Scale Meteorology & Air Quality Models - School of Architecture ...

ASI2_Lecture 3_7/12/2011
erturbations nique inks to etup xploration
Taking the model’s
• Fine scale modeling enters the “Terra Incognita” regime
• Given that mesoscale modeling systems have many
operating options, how are the resulting simulation
dependent on the user selection of model options.
• Need to understand the properties of modeling systems
dependence on the properties of their individual
components and their linkages.
• Ad hoc modeling group is currently undertaking this study,
preliminary results follows.
• Perform & explore model sensitivity studies including:
Model physics, numerics, time steps, grid size, filtering
ASI 2: URBAN CLIMATE AND AIR POLLUTION School of Architecture, The Chinese University of Hong Kong, Hong Kong, 7-8 Dec 2011
Numerical Considerations: Horizontal Diffusion
Standard configuration of WRF has in the horizontal the Smagorinsky scheme
K
h
s
C x
2
s
C 0.4
2
u
v
0.25
2 2
x
y
ASI 2: URBAN CLIMATE AND AIR POLLUTION School of Architecture, The Chinese University of Hong Kong, Hong Kong, 7-8 Dec 2011
2
2
u
v
y
x
In Martilli’s simulations, with DX=1km, this gives K h values of the order of 100-200 m2/s
Standard MM5 has in the horizontal (see Xu et al. MWR 2001)
K
K
h
H 0
K
H 0
3. 10
2
2
2 2 u
v
u
v
Cs
x
0.25
2 2
x y
y x
3
x
t
2
2
600.
m 2 //s
s
For Dx=1000.m and Dt=5s (Martilli’s case)
“the background term K H0 is dominant at all levels and locations
throughout the simulation time” Xu et al. MWR 2001
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