Solid-state Weather Radarmade in JAPANJapan Meteorological Agency
Ministry of Land, Infrastructure, Transport and Tourism
Ministry of Internal Affairs and Communications

Worldwide prevalenceof extreme weather events
A range of extreme weather events, including heat waves, blizzards, heavy rain and massive
snowfall occur all over the world, bringing serious damage on a global scale.
To address this threat and mitigate related damage, there is a pressing need for highly accurate
observation data indicating current conditions.

Advanced weather radarfor a disaster-prone nation
Why is advanced weather radardevelopment promoted in Japan?

Advanced solid-state weather radarfor detailed observation

Located in the Asian monsoon region, Japan is frequently hit byextreme natural disasters involving typhoons, heavy rain, ﬂooding
and landslides. Against such a background, there has been aneed for meteorological observation data with ﬁner resolution andgreater precision to mitigate related damage. To meet this need,
updates to introduce more advanced techniques for weather
radar and other observation equipment have constantly beenrequired since the ﬁrst weather radar started operation in Japanin the 1950s. This situation has positioned Japanese solid-state
weather radar as a pioneer in the global market.

Early weather radar was capable of detecting only areas ofrain, but has developed gradually in line with the needs of thetimes to enable observation of rain intensity, wind velocity andthe shape of raindrops on a step-by-step basis. This has led
to t h e r e c e n t e s t a b l i s h m e n t o f we a t h e r r a d a r wi t hsemiconductor transmitters replacing the previous electron
tubes. Such units are ready for practical use, and are being
installed for operational application in Japan by the Japan
Meteorological Agency and other organizations.

Advantages of solid-state weather radar

High accuracy

Reducedrunning costs

Improved stability
andmaintainability

More effective
use ofradio waves

History of on-site weather radars in Japan
Gradual improvement

1954 – 1968

1950s – 1970s

1965 – 1999

2016 –First operational weather
radar

Early weather radar monitoring
equipment

Historical landmark:installation of the world’s highest
weather radar on top of Mt. FujiCutting-edge dual-polarization
solid-state weather radarSolid-state Weather Radar – Advantage 1

High accuracy
A combination of stable radio wave output and cutting-edge observation techniques basedon dual polarization reduces observation time and increases data accuracy.

Increased precision
Comparison of radar-based and on-site raingauge observation
The ﬁgures below show rain intensity observed using new (dual-polarization solid-state)/conventional radar techniques and on-siteraingauge observation. The new radar approach supports highly accurate observation.
Rain intensity observation using conventionaland new radar technology
Conventional weather radar

Dual-polarization solid-state weather radar
200

Improvement

200

370
15:00

150
36.5
125
100

3675

35.5

15:10

15:20

15:30

15:40

15:50

50

16:00

Dual-polarization radar enables highly accurate observation based on horizontally andvertically polarized waves.

●Stable radio wave output is essential for dual-polarization observation over a short time span.

125
100

3675

35.5

50

2535

[ Dual-polarization radar ]
●

175
150
36.5

Latitude

50

37
175

R e su l t s f r o m t h econventional radarappr oa ch sh ow
Signiﬁcant differencesfrom those of on-siteobservation.

Rain intensity (mm/h)

100

0139

140

Longitude●●14150 km

25350139

140

Longitude14150 km

Shaded areas show rain intensity observation results from each radar technique.
Red arrows show locations of on-site raingauge observation.

Rain intensity (mm/h)

150

Results from the newr ada r show cl ose
correspondence toth o se o f o n -s i teobservation.

Latitude

Rainfall intensity (mm/h)

200

Solid-state Weather Radar – Advantage 2

Reduced running cost
Running costs can be drastically reduced by extending the life of transmitters andcutting power consumption.

Initial cost

Approx. the sameas electron tube
weather radar

Running cost

Running cost(maintenance/part replacement)(power consumption)

Cost reduction

Cost reduction

Reduced cost●

Solid- state transmit ters last over 10 years with fewer technical problems thanelectron tube transmitters, which require tube replacement every few years.

●

Solid-state transmitters work without a high-voltage electricity supply.

Solid-state Weather Radar – Advantage 3Improved stability & maintainability
Solid-state transmitters continue operating even in the event of semiconductor device issues,and problem devices can be replaced without shutting down the whole radar system.

Electron tube transmitters

Solid-state transmitters●

Radar operation cannot continue in the event of electron
tube malfunction.

●

If a problem arises with a modular par t, operation can becontinued with reduced output.

●

The system must be shut down for electron tube replacement.

●

It is unnecessary to shut down the system during replacement,
and adjustments can be easily made due to the low voltage used.

●Solid-state transmitters are around half the size of electron
tube transmitters.

Improved continuity

Solid-state Weather Radar – Advantage 4

More effective use of radio waves
The narrow bandwidth of transmitted radio waves enables more effective use of radio wave
resources.

Reduced channel interval
Example in Japan
Radio wave bandwidth allocated to each weather radar in the operation of multiple weather radars
Using a solid-state transmitter makes it easy to shape the wave form.

●Consequently, the interval of the allocated bandwidth was halved to 5 MHz.

Electron tube
weather radar

Electric power waveform oftransmitter-produced radio waves

Power●Solid-stateweather radar

10 MHzPowerFrequency

Frequency

10 MHzIntroduction to operational use in JapanThe Japan Meteorological Agency(JMA)

Water and Disaster Management
Bureau, MLIT, Japan

Trial observation with solid-state weather radar
was started at JMA’s Meteorological ResearchInstitute in 2007, and the Agency upgraded its
aviation weather radars with solid-state technology
at Haneda, Narita and Kansai airports in 2016. The
approach is also currently being deployed at otherairports, and its adoption for the Agency’s
general-purpose weather radars is planned.

In 2010, practical operation of dual-polarization solid-state radars
was im plemented for s ome X- band radars to suppor t them anageme nt of r ive r fac ilities by the Water and Disaster
Management Bureau of Japan’s Ministry of Land, Infrastructure,
Transport and Tourism (MLIT). Some conventional C-band radars
hav e be e n up date d todual-polarization
solid-state types, and aun ite d r ada r p r o d u c t
based on the use of bothbands entered practicaloperation in 2016.

Haneda Airport RadarApprox. 20% reduction in power consumption
for the whole system compared to a Klystron
Before(kWh)25000

After20000
Composite map of observation by X- and C-band radars

15000
10000

Radar product speciﬁcations

5000

Observation interval

Spatial resolution

Transmission time

1 min

250 m

1 – 2 min

0AprMay

JunJulAug

SepOctNovDecCountries adopting Solid-state Weather Radarmade in JAPAN●

Australia●

Belgium●

Croatia●

Denmark●India●Indonesia●Japan●Myanmar●Philippines●

Singapore●USA(As of January 2017)

Contact
Japan Meteorological Agency
Ofﬁce of International Affairs
iao-jma@met.kishou.go.jp+81-3-3211-4966

Ministry of Internal Affairs and Communications
International Cooperation Division+81-3-5253-5934