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 directoriesThe 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.
|
