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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 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 17km 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, Procedure of NWP

Procedure of NWP



Model Horizontal
(Vertical Layers)
Simulation/day Prediction Period Remarks
Global Prediction Model(GDAPS) 17 km (70) 2(00.12UTC) 12 days Global domain
2(06,18UTC) 3 days
32 km(70) 2 12 days Ensemble forecasting
60 km(85) 1 220 days Seasonal Forecasting
Regional Prediction Model (RDAPS) UM 12 km(70) 4 87 hours East Asia
Local Prediction Model(LDAPS) UM 1.5km(70) 4 36 hours East Asia
Wave Model 1 km 2 3 day 5 Coastal domains
along Korean peninsula
8 km 2 87 hours Asia domain
50 km 2 12 days Global domain
Regional Tide/Surge Model (RTSM) 8 km 2 87 hours Asia domain
Asian Dust and Haze Model(ADAM2-Haze) 25 km(49) 4 3 days Asia domain
Statistical Model(MOS) 5km, 700points 2 12 days 11 element
(digital forecast element)

Forecast chart of global prediction model.Forecast for Northern Hemisphere(Height and temperature at 500hPa)

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 accumulated precipitation

Forecast chart of regional model.
Mean sea level pressure and 6 hour
accumulated precipitation

Forecast for weather guidance(every 3 hour)

Forecast for weather guidance
(every 3 hour)

I. Recent changes

KMA installed new supercomputer(CRAY XC40) which had 5.8PF (Peta Flops) capacity and upgraded the global model by improving model dynamic core and increasing model resolution from 25km to 17km in 2016. Also, global ensemble model, which had 40km horizontal resolution and 24 members, was upgraded to 32 km resolution model with 25 members. Local model with 1.5 km resolution was also improved. Its domain was extended to cover the East Asia region including Japan and east part of China.