Outline of the Operational Numerical Weather Prediction at the Japan Meteorological Agency (JMA)

1. Computer System

The computer system at JMA consists of a Hitachi S-3800/480 supercomputer, general purpose servers, workstations, X terminals, personal computers and numbers of peripheral equipment.

The supercomputer (Hitachi S-3800/480) is used primarily for operational numerical weather analysis and prediction, and development of NWP (Numerical Weather Prediction) system. The S-3800/480 has 4 high performance vector processors and 4 scalar processors which can simultaneously operate and have access to the same main memory. The peak vector performance of each vector processor is 8 GFLOPS, and the total peak performance of the S-3800/480 is 32 GFLOPS. The supercomputer has a 2-Gbyte high performance main storage memory and 12-Gbyte extended storage memory (ES) for temporary files and permanent files in order to shorten input/output access time. The operating system of the Hitachi S-3800/480 is the Hitachi VOS3/AS/HAP, which is compatible with that of the Hitachi general purpose server except vector operations.

An automated Cassette Magnetic Tape (CMT) Library (CMTL) unit is used to store NWP results. The library unit contains about 5000 volumes of CMT (compatible with IBM3490 type, 36 tracks) and CMTL has a capacity of 2.1Tbytes as each volume of CMT has a capacity of 400 Mbytes.

2. Objective Analysis System

Four kinds of objective analyses for meteorological fields are performed: global analysis for the Global Spectral Model (hereafter GSM9603 or GSM), regional analysis for the Regional Spectral Model (RSM9603 or RSM), typhoon analysis for the Typhoon Model (TYM9603 or TYM), and upper stratospheric analysis for the one-month forecast model. Specifications of the JMA analysis system are summarized in Table 1. The global and regional analyses are carried out by using a multi-variate three-dimensional optimum interpolation method on the grid of the corresponding forecast models. The typhoon analysis is basically the same as the global analysis except that the typhoon analysis is performed only in the western North Pacific and adjacent areas. The upper stratospheric analysis is carried out by using a function fitting method on pressure surfaces above 10 hPa.

Table 1. Specifications of the JMA objective analysis system

Analysis model	Global analysis	Regional analysis	Typhoon analysis	Upper stratospheric analysis
Analysis time	00, 06, 12, 18 UTC	00, 12 UTC	06, 18 UTC	00, 06, 12, 18 UTC
Data cut-off time	Early analysis: 2.5h (00 UTC), 3.0h (12 UTC)	3.0 h (00 UTC) 3.5 h (12 UTC)	1.5 h	Early analysis: 3.0h (12 UTC)
	Cycle analysis: 13.0h (00 UTC), 7.5h (06 UTC), 12.0h (12 UTC), 6.5h (18 UTC)			Cycle analysis: 13.0h (00 UTC), 7.5h (06 UTC), 12.0h (12 UTC), 6.5h (18 UTC)
Grid system	Gaussian grid	Lambert projection	Same as global analysis	Latitude-longitude
Horizontal resolution	0.5625	20 km at 60N and 30N	0.5625	2.5
Number of grid points	640 x 320	257 x 217	321 x 217	144 x 73
Vertical levels	surface + 30 levels up to 10 hPa	surface + 36 levels up to 10 hPa	Same as global analysis	7, 5, 3, 2, 1, 0.4 hPa
Analysis variables	Ps, Z, u, v, T, RH	Ps, Z, u, v, T, RH	Ps, Z, u, v, T, RH	Z, T
First guess	6 hour forecast by global model	12 hour forecast by regional model	6 hour forecast by global model	Analysis 6 hours before
Analysis method	3-dimensional optimum interpolation on model levels	3-dimensional optimum interpolation on model levels	Same as global analysis	Function fitting on pressure surfaces

^#Global sea surface analysis on 1 x 1 grids is carried out everyday.

3. Forecast Models

Specifications of the main operational NWP models at JMA, the Global Spectral Model (GSM), the Regional Spectral Model (RSM), the Typhoon Model (TYM) and the One-month Forecast Model are listed in Table 2.

Table 2. Outline of the numerical weather prediction models at JMA

	Global Spectral Model	Regional Spectral Model	Typhoon Model	One-month Forecast Model
Objectives	Medium-range forecast, Typhoon track forecast	Short-range forecast	Typhoon track forecast	One-month forecast
Forecast Domain	Global	East Asia & adjacent seas	Relocatable in the western North Pacific	Global
Grid Size & Number of Grids	0.5625 / 640x320	20 km / 257x217	40 km / 163x163	1.875 / 192x96
Map Projection	.	Lambert	Mercator (Lambert) for typhoon south (north) of 20 KN at T+0 h	.
Vertical Levels	30 levels up to 10 hPa	36 levels up to 10 hPa	15 levels up to 30 hPa	30 levels up to 1 hPa
Major Physical Processes	.	.	.	.
Radiation (Solar)	Every hour	Every hour	Every hour	Every hour
(Infrared)	3 hourly	Every hour	Every hour	3 hourly
Cumulus Convection	Arakawa-Schubert (1974)	Arakawa-Schubert (1974)	Arakawa-Schubert (1974)	Arakawa-Schubert (1974)
Mid-level Convection	Mass-flux type	Moist convective adjustment	Moist convective adjustment	Mass-flux type
Grid Scale Cond. & Evap.	Included	Included	Included	Included
Land Surface	SiB	Constant	Constant	SiB
Forecast Hours	84 h (0000 UTC), 192 h (1200 UTC)	51 h (0000, 1200 UTC)	78 h (0600, 1800 UTC)	30 days (5 runs twice a week)
Initial Fields	Global analysis	Regional analysis	Typhoon	Interpolated from global analysis
Lateral Boundary Conditions	.	0-51 h global forecast from T+0 h	6-84 h global forecast from T-6 h	.
Forecast Phenomena	Large- and synoptic-scale	Synoptic- and meso-scale	Typhoon	Long-term large-scale

RSM is the main model for short-range weather forecast and supports objective forecast guidances processed with Model Output Statistics (MOS), Kalman Filter and Neural Network.

TYM has an identical dynamical framework and physical processes to those of RSM. Typhoon prediction is performed four times a day whenever a typhoon exists in the western North Pacific: GSM makes 84- and 192-hour predictions from 0000 and 1200 UTC, respectively, and TYM does 78-hour ones from 0600 and 1800 UTC. Both models support the activities of the RSMC (Regional Specialized Meteorological Center) Tokyo Typhoon Center of WMO (World Meteorological Organization).

4. Objective Forecast Guidances

a. Kalman Filter

The Kalman Filtering technique is used to prepare short-range forecast (up tp 51 hours) guidance products, such as probability of precipitation, 3 hour precipitation amount, surface air temperature and surface wind speed. The guidance products of precipitation and surface air temperature are calculated at every grid point with 20km intervals. The guidance products of surface wind speed is prepared for local forecast at aerodromes.

b. Neural Network

Three layered neural networks are also used to produce some of the short range-forecast guidances. Wmap (categorized weather), PoHP (probability of heavy precipitation), PoT (Probability of thunderstorm) and RHmin (daily minimum relative humidity) are prepared by neural network using RSM predictions. Wmap is calculated on every square grid of 20km x 20km area including Japan. PoHP and PoT are calculated for every local meteorological observatory's responsibility area. Daily minimum relative humidity (RHmin) is calculated at 71 meteorological observatories.

c. One-week forecast guidance

One-week forecast guidances are produced for PoP (probability of pricipitation (1mm/day)), MRR (daily area mean precipitation amount), RoCA (ratio of cloud amount), Tmax (daily maximum surface temperature), Tmin (daily minimum surface temperature) and Tmean (daily mean surface temperature). The Model Output Statistics (MOS) technique is used to make PoP, MRR and RoCA and the Kalman Filtering technique is used to make the temperature guidances. The development is under way to change the method of producing PoP, MRR and RoCA to Kalman filtering technique.

5. Tracer Transprot Model

JMA has established a RSMC for environmental emergency response (EER). When radioactive accidents occur, tracer transport model will be run to provide trajectories, low-level concentrations and depositions for the RA-II members.

6. Support to foreign countries and meteorological business

The member countries of Typhoon Committee of WMO can have an access to RSMC data server of JMA through the internet and international ISDN line and utilize NWP products of JMA for their operational forecasting.

NWP products including GPV data are provided to weather companies through MBSC (Meteorological Business Support Center) and utilized on online and offline basis.

7. Future plan

(2) Ocean-atmosphere coupled model will be operated from 1998 to predict El Nino event.

(3) Ensemble medium-range forecats will be put into operation in 1999 to supprot one-week forecast.

(4) The 3-D VAR for the global analyasis will be implemented in 1999.

References

NPD/JMA, 1997: Outline of the Operational Numerical Weather Prediction at the Japan Meteorological Agency, Appendix to Progress Report on Numerical Weather Prediction, 126pp.