A numerical weather model is the computer program that simulates an atmospheric motion in space and time. A variety of weather phenomena can be analyzed and predicted by the different types of numerical weather prediction models.
In the model the atmosphere is assumed to be composed of a number of lumps in which corner points are called as the grid points. The more number of lumps indicates the more elaborate simulation. Simulation by the model generates the future state of the model atmosphere at all grid points from its initial state.
Products of numerical models are serviced to forecasters as well as public on the web-site through Internet dedicated as a delivery system. In particular, forecasters use these products as guidance with their expertise and experiences for an issue of weather forecasting. Besides, many other models such as statistical model, ocean wave model, and typhoon model, etc., are employed to exploit the output produced from the weather forecast model for their purposes.
With the operational supercomputer NEC/SX-5, the KMA could run several numerical models in 1999. Recently, KMA introduced Unified Model (UM) and data assimilation (4DVAR) system from UK Met Office to improve NWP performance. UM-based global and regional NWP system installed on a new supercomputer CRAY/XE6 are being operated since May 2010.
Procedure of NWP
|Global Prediction Model(GDAPS)||25 km(70)||2(00,12UTC)||10 days||Global domain|
|40 km(70)||2||10 days||Ensemble forecasting|
|110 km(21), T106||1||120 days||Seasonal Forecasting|
|Regional Prediction Model(RDAPS)||UM 12 km(70)||4||3 days||East-Asia domain|
|WRF 10 km(40)||4||3 days||East-Asia domain|
|Korea Local Analysis and
Prediction System (KLAPS)
|5 km(40)||24||12 hours||Korea domain|
|Typhoon Model (DBAR)||35 km(1)||4
(when Typhoon generated)
|3 days||Typhoon tracks|
|Wave Model||1 km||2||1 day||6 Coastal domains
along Korean peninsula
|8 km||2||3 days||Asia domain|
|50 km||2||10days||Global domain|
|Regional Tide/Surge Model (RTSM)||8 km||2||3 days||Asia domain|
|Asian Dust Aerosol Model (ADAM)||30 km(29)||2||3 days||Asia domain|
Forecast chart of global prediction model.
Forecast for Northern Hemisphere
(Height and temperature at 500hPa)
Forecast chart of regional model.
Mean sea level pressure and 6 hour
Forecast for weather guidance
(every 3 hour)
I. Model Configuration
|Basic equation||Complete equation|
|Horizontal Resolution||Grid points of horizontal resolution with N512, corresponding to a grid size of 0.352Ⅹ0.234 degrees or 25km|
|Levels||70 vertical levels ranging from sfc. to 80km|
|Time Integration||Semi-implicit /Semi-Lagrangian scheme|
|Convection process||Mass flux convection with CAPE closure|
|Microphysics processes||Mixed-phase precipitation|
|Radiation||Edwards-Slingo general 2-stream scheme|
|Gravity wave drag||G.W. drag due to orography(GWDO)|
|PBL processes||MOSES-Ⅱ Non-local PBL|
|Land surface||MOSES-Ⅱ land-surface scheme|
|Method||4DVAR(4 Dimensional Variational method)|
|Observation time window||-3hr ~ 3hr|
|VAR Innerloop /levels||N144(90km) / 70 layers (Top : 80km)|
|Observation species||Surface, Sonde, Aircraft ,ATOVS, Satwind, Scatwind, SSMIS, IASI, AIRS, GPSRO, etc.|
|Typhoon bogus||Observation bogussing for wind and MSLP|
II. Operational aspects
Global Model (GDAPS) for 10-day forecast runs at 00UTC and 12UTC with 2 hours and 25 minutes data cutoff. The 3-day forecast is also provided at 06UTC and 18UTC. The 3-day projection is used for the provision of lateral boundary condition for regional models, and prognostic/diagnostic variables from the global model are used as input for the application models such as yellow dust model and global wave model.
III. Recent changes
The GDAPS which is based on the Unified Model (UM) introduced from Met Office has been operated on KMA’s 3rd supercomputer (Cray XE6) since 14th May 2010. The horizontal and vertical resolution of the global model was enhanced from 40km/50 layers to 25km/70 layers in May 2011.