Operational Mesoscale NWP at the Japan Meteorological Agency Tabito HARA Numerical Prediction Division Japan Meteorological Agency
NWP at JMA JMA has been operating two NWP models. GSM (Global Spectral Model): for shortterm and weekly weather forecasts. MSM (Meso scale model): for disaster prevention. (Regional Spectral Model (RSM), which had provided short-term weather forecasts, was stopped to operate in Nov. 20, 2007) Global Spectral Model (20km) Meso Scale Model (5km) (for disaster prevention)
Contents MSM (operational Meso Scale Model at JMA) Purpose Operation Brief history Specification Examples by MSM Advantages of frequently updated forecasts
MSM: the operational mesoscale model at JMA Purpose To provide information for disaster prevention, especially phenomena such as heavy rain and strong wind. Covering Japan and its surrounding area. Horizontal grid spacing : 5km (since March, 2006) Employing NHM as the NWP model of MSM since Sep., 2004. Until then, hydrostatic model with 10-km horizontal resolution was used.
Operation of MSM Updated every 3 hours Initial time: 00, 03, 06, 09, 12, 15, 18, 21UTC Fresh observations can be included through the assimilation process. 33-hour forecasts are delivered 4 times a day (03, 09, 15, 21UTC). This makes it possible to provide information up to 24 hours ahead. 15-h forecasts in 00, 06, 12, 18UTC
Outputs of MSM are used by: Short-term weather forecast Very short range forecast of precipitation (VSRF) Combined with extrapolation of observation Forecast for aviation (TAF) Forecast of a storm surge
Computational domain 2900 km 3600 km The domain covers Japan and its neighborhood, which has not been changed since the beginning of MSM operation.
Brief history of MSM(1) In Mar. 2001 Started to operate with hydrostatic model. Horizontal resolution = 10km Provide 18-hour forecast 4 times a day In Mar. 2002 Started to operate 4DVAR analysis system based on hydrostatic model. In Sep. 2004 JMA-NHM (non-hydrostatic model being developed by NPD and MRI) was employed as MSM instead of the former hydrostatic model. The horizontal resolution, frequency of update, domain were the same as the former one.
Brief history of MSM(2) In Mar. 2006 Horizontal resolution was enhanced: 5km Frequency increased: 15-hour forecast 8 times a day Some improvements for physical processes In May 2007 Forecast period was extended: 33-hour forecasts 4 times a day out of 8 times. Many physical processes have been refined. In Nov. 2007 The model providing boundary conditions was replaced: from RSM to 20km GSM. In Mar. 2008 JNoVA, the 4DVAR analysis system based on NHM will be installed.
Case of Niigata-Fukushima heavy rain in July, 2004 OBS Hydro. MSM10km Non-Hydro MSM5km (MSM0603) in operation then Non-Hydro MSM10km (MSM0409) Non-Hydro MSM5km (MSM0705)
Current specifications of MSM(1) JMA-NHM, which is being developed at MRI and NPD/JMA, has been employed as the model for MSM. Horizontal grid spacing: 5km (721x577) Horizontal discretization Arakawa-C (staggered) Number of vertical layers: 50 Vertical coordinate terrain following hybrid (z*-z hybrid) Time step : 24sec To operate stably with the relatively large time step, splitting of advection, time splitting of gravity waves are adopted. Computational Time about 30min. for 33-hour forecast with 72 nodes on SR-11000 (supercomputer produced by Hitachi).
Current specifications of MSM(2) Dynamics Sound waves: HE-VI (Vertically implicit, horizontally explicit and time splitting) Advection: Flux form 4-th order with advection correction and time splitting Gravity waves: Time splitting
Current specifications of MSM(3) Physical Processes Moist process 3-ice bulk cloud microphysics Modified Kain-Fritsch convective parameterization Turbulence Process Improved Mellor-Yamada Level 3 Radiation Process Mostly the same as GSM0412, in which clear sky radiation is well refined. Cloud fraction and amount of cloud water in the radiation process are diagnosed with the partial-condensation scheme. Surface Process Slab model in which ground temperature are predicted with 4-layer heat diffusive model, and soil water is also predicted with force restore method. Surface flux is evaluated with the scheme suggested by Beljaars and Holtslag.
Current Specifications of MSM(4) Data assimilation Cut off time: 50 min. from each initial time. Meso4DVARbased on hydrostatic model with horizontal resolution 10km. (not the same as forecast model) Assimilated observation Conventional surface and upper obs. Analysis of precipitation with radar observation calibrated by rain gauge. Radius wind obtained by Doppler radar Wind profilers Satellite observation such as radiance temperature, wind determined by motion of clouds.
Current Specifications of MSM(5) Boundary Conditions 20km GSM at JMA is used as boundary conditions. RSM was replaced as the model providing boundary conditions to MSM by 20 km GSM when 20 km GSM was started to operate as a model for short-term weather forecasts, in Nov. 21, 2007.
Example of Typhoon forecasts by MSM
Example of Typhoon forecasts by MSM Simulated Satellite Image Typhoon 0709 -Sep. 06, 2007 Initial Simulated Satellite Image OBS. By MTSAT-1R
Advantages of frequently updated forecasts(1) The latest observations can be assimilated to capture short-lived, small scale phenomena. By comparing results of different initials, how much the forecasts are trustworthy are examined. Possible to prepare two or more scenarios. Generally, quality of precipitation forecast by NWP is degraded as the forecast time proceeds. Precipitation forecasts include uncertainty.
Advantages of frequently updated forecasts(2) Time series of threat score for precipitation over 1mm/3h of each initial time. For several hours from each initial time, the best prediction can be obtained by adopting the latest one.
Case:Mar 16, 2006 06UTC 3hour precipitation Obs Precipitation over 10mm/3hr was observed, separated to 2 areas. First, it was forecasted like one belt, but newer forecast became similar to observation. Precipitation over 20mm/3hr was observed. It was forecasted from first to last. Reliability of this forecast is considered higher. MSM T+09 MSM T+12 MSM T+15
Case:Apr 04, 2006 21UTC Obs 21UTC Two heavy rain bands were observed. The rain band of the north side was hardly represented, while it was too hard in the southern side. MSM 12UTC FT=09 MSM 09UTC INI FT=12 Two precipitation bands could be predicted in older forecast, although newer one is better statistically. Like this case, the newest one is not always better, but several possible scenarios can be provided.
Future Plan More refinements are being aimed, such as Improvement of convective parameterization (KF scheme) Introduction of new land surface model (MJ-SiB) 2-moment cloud microphysics JNoVA 4DVAR will be installed soon. It can provide more compatible initial condition, and its contribution to more accurate prediction is highly expected. Local Forecast Model (LFM), of which horizontal resolution is planned to be about 2 km, is also being developed, aiming to deliver finer prediction.