Geoscience Reference
In-Depth Information
2. Model Description, Cyclone Bogusing and
Experiments
Table 1 lists the WRF model specifications used in the present study. Figure 1
shows the geographic domain of the model experiments and terrain height
(km) above mean sea level. The model has single domain at 27 km grid
resolution with 301 grids west to east and 275 grids south to north points
covering both Bay of Bengal and Arabian Sea.
In the TC vortex bogusing scheme (Davis and Low-Nam, 2001) any vortex
within 300 km radius of influence (from the observed location) is first removed
from the background first guess, and then an axis-symmetric vortex is inserted
at observed TC location. This relocation procedure uses observed cyclone
parameters (location, intensity and radius of maximum wind etc. (obtained
from NCEP TCVITALs). The new specified bogus vortex takes the form of a
deviation from this environmental field so that it can be easily merged with the
latter field at the correct position (Ashrit et al., 2006). By bugusing, winds,
temperature, and humidity fields at vertical levels and the surface pressure
fields get modified. To study the impact of TC bogusing, four experiments are
carried out for three cyclones Laila, Giri and Phet of year 2010. The four
experiments are summarized in Table 2.
Table 1:
WRF model configuration details
Model
WRF-ARW
Version
3.2
Horizontal resolution
27 km
Horizontal staggering
Arakawa-C Grid
Vertical levels
38
Topography
USGS
Time integration
Semi Implicit
Time steps
90 s
Vertical differencing
Arakawa's Energy Conserving Scheme
Time filtering
Robert's method
Horizontal diffusion
2nd order over quasi-pressure surface,
scale selective
Convection
Kain-Fritsch (Kain and Fritsch, 1990,
1993)
PBL
YSU scheme
Cloud microphysics
WSM3-Class Simple Ice
Radiation
RRTM (LW), Dudhia (SW)
Gravity wave drag
No
Land surface processes
Thermal diffusion
Search WWH ::
Custom Search