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Numerical Weather Prediction

Numerical Weather Prediction (NWP)

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/surge model, and typhoon model, etc. are employed to exploit the output produced from the weather forecast model for their purposes.

KMA started to run numerical weather forecast model from 1999 with the introduction of 1st supercomputer(NEC/SX-5). The performance of KMA model has been significantly improved since KMA introduced Unified Model (UM) from UK Met Office in 2010. Now, KMA is operating 10km global model with hybrid data assimilation system, 12km regional model coupled with 4DVAR(4Dmensional VARiational data assimilation) and 1.5km local model with 3DVAR. Also, Global Ensemble model with 32 km resolution and 25 members and local ensemble model with 3km resolution and 13 members are being operated.


Model Horizontal
Resolution
(Vertical Layers)
Simulation/day Prediction Period Remarks
Global Prediction Model(GDAPS) 10 km (70) 2(00,12UTC) 12 days Global domain
2(06,18UTC) 3 days
Global Ensemble Model(GDAPS) 32 km(70) 2(00,12UTC) 12 days Global domain
(25members)
Seasonal Forecast
System
60 km(85) 1 220 days Seasonal Forecasting
Regional Prediction
Model (RDAPS)
12 km(70) 4 87 hours East Asia
Local Prediction Model
(LDAPS)
1.5km(70) 4 36 hours East Asia
Very Short Range
Forecast Model (VDAPS)
1.5km(70) 24 12 hours Korean Peninsula
Local Ensemble Model
(GDAPS)
3km(70) 2 72 hours Korean Peninsula
(13 members)
Coastal Wave Model
(CWW3)
1 km 2 3 days 5 Coastal domains along Korean peninsula
Regional Wave Model
(RWW3)
8 km 2 87 hours Asia domain
Global Wave Model
(GWW3)
50 km 2 12 days Global domain
Regional Tide/Surge
Model (RTSM)
8 km 2 87 hours Asia domain
Asian Dust Aerosol
Model 2 (ADAM2)
25 km(47) 4 3 days Asia domain
Asian Dust Aerosol
Model 3 (ADAM3)
25 km(49) 4 3 days Asia domain
Statistical Model
(MOS, PPM)
5km, About 700points 2 12 days 11 element
(digital forecast element)

I. Recent changes

In 2017, Variational Bias Correction (VARBC) for satellite data was introduced to correct the bias of satellite data more elaborately. Also, perturbation of surface variables was added in global ensemble model to give more realistic ensemble spread of surface variables.
In 2018, the resolution of global model was changed from 17km to 10km and background error covariance of global model was updated with newly trained global model output, improving the global model performance.