MM5 model setup:
The 3D dynamic non-hydrostatic prognostic
meteorological model MM5
uses three nested domains to simulate mesoscale atmospheric dynamics
taking nitial and boundary conditions from the GFS Forecast model and generates
local high-resolution data sets.
The largest domain has horizontal resolution of 27 km in both directions and
extents 58x58 grid points. The two nested domains have 9 km resolution with 82x82
grid points and 3 km resolution with 109x109 grid points.
The final domain is identical to the model (CAMx) master domain, with a 1 km resolution
generated by MM5toCAMx:
Central coordinates for mother (largest) outer model domain are: 51.24°E, 35.67°N
The projection used in MM5 computations is Lambert-Conformal projection.
The MM5 model output is converted to a UTM grid after
the model run using MM5toCAMx postprocessing program.
Vertical resolution of the model domain consists of 17 levels plus surface (1000 mb).
The model has a high vertical resolution near the surface to
cover layering used by CAMx. The vertical levels are distributed as follows
(in mb): 1000, 997, 994, 988, 976, 940, 883, 850, 780,
700, 600, 500, 400, 300, 250, 200, 150, 100.
The computational time step for the largest domain is 81 s.
The timestepping increases by factor 3 for nested domains. Approximately 3 times
horizontal grid resolution in km. Model output frequency is 1 h.
Integration time of the model is 2+24 hours for three consecutive days.
MM5 data (except precipitation and cloud water) are calculated from
midnight to midnight next day in local time, 00:00 local time till 24:00
local time, all together included = 25 timesteps. Last timestep (24:00
local time) is overwritten with the next day forecast (00:00).
Precipitation and cloud water data have 24 timesteps from 00:00 local
time till 23:00 local time.
There is also one version starting at 18:00 UTC and finishing at 24:00 UTC
next day = 30 hours. The first 2 hours "startup" are discarded, that means it
would import data from 20:00 UTC or midnight local time. The simulation
finishes at 24:00 UTC or 3:00 local time next day. The last 3 hours are
redundant, but they are necessary for historical scenarios because
boundary conditions are only available at 24:00 UTC. FNL data don't have
output at 21:00 and the model needs boundary conditions
for the whole duration.
The last timestep imported is 21:00 UTC or midnight next day local time.
Last 3 hours are not used.
Starting at 18:00 UTC and finishing at 21:00 UTC next day = 27 hours.
25 hours from local midnight to midnight next day.
The toal forecast peropd displayed is 3*24 (72 hours)
without any overlapping.
The model setup takes into account the local time shift
from UTC of 4 h (not 3.5 hours). Start time of forecast simulation is at
18:00 UTC "today" and end time of forecast simulation is 24:00 UTC "tomorrow".
Data are imported and displayed for 24 h corresponding to local time
00:00 to 24:00 h (with half an hour shift).
MM5 INPUT DATA: files and directories
The MM5 input files for
TEHRAN forecast come from the NCEP GFSmodel.
The data are downloaded from one of the available Real Time NOMAD
servers at NCEP or NCDC (http://nomad1.ncep.noaa.gov/):
and located on both the
- primary application and web server;
- the COMPUTE SERVER for the application.