٨A Case of Utilizing Results

Trial distribution ofX-band MP radarrainfall information



TSUCHIYA Shuichi, Researcher
KATO Takuma, Researcher
Water and Management and Dam Division

KIKUMORI Yoshito, Senior Researcher
River Division
River Department1. Introduction
Flood disasters caused by so-called guerrilla rainfall,the 2008 flood on the Togagawa River in Kobe City,
Hyogo Prefecture, or the water accident on the mainline of the Zoshigaya Sewer System in Toshima Wardin Tokyo for example, have occurred frequently inrecent years. The River Bureau of the Ministry ofLand, Infrastructure, Transport and Tourism isintroducing X-band Multi-Parameter radar (below
called X-MP radar), a type with high special andtemporal resolution, in order to perform refinedobservations and monitoring of guerrilla radar.
2. Characteristics of conventional radar andnewly-installed X-MP radar
The conventional MLIT C-band radar (radius ofquantitative observation range: 120km, 1km mesh),which provides wide observation range and is installed
to cover the entire nation, is a large riverflood-management tool useful in observing theseasonal rain front or typhoons, but its observation
mesh is too large to allow its use for precise
observation of local and sudden guerrilla rainfall. In
contrast, the newly installed X-MP radar (radius ofquantitative observation range: 60km, 250m mesh)uses small observation meshes which permit highresolution rainfall observations, allowing users totemporospatially clarify the constantly changing stateof rainfall (Fig. 1).
Rainfall legend

Rainfall legendNo data

No dataObservation᷹ⷰ㑆㓒5୚
interval:
5Xಽ⸃⢻16୚
Resolution:16X

[C-bandradar (conventional radar)]䇼䌃䊋䊮䊄䊧䊷䉻䋨ᣢሽ䊧䊷䉻䋩䇽
Spatialresolution: 1km × 1km square meshesⓨ㑆ಽ⸃⢻䋺1km㬍1km䈱⋥ⴕ䊜䉾䉲䊠
Radiusof quantitative observation range: 120km
ቯ㊂᷹ⷰ▸࿐ඨᓘ䋺120䌫䌭᷹ⷰ㑆㓒䋺5ಽ
Observationinterval: 5 min.
Time
until observation data transmission: 5 to 10 min.
᷹ⷰ䊂䊷䉺㈩ା䉁䈪䈱ᤨ㑆䋺5䌾10ಽ

[X-bandMP radar (From July 2010)]
䇼䌘䊋䊮䊄䌍䌐䊧䊷䉻䋨2010ᐕ7᦬䌾䋩䇽Spatialresolution: 250m × 250m square meshesⓨ㑆ಽ⸃⢻䋺250m㬍250䌭䈱⋥ⴕ䊜䉾䉲䊠
Radiusof quantitative observation range: 60km
ቯ㊂᷹ⷰ▸࿐ඨᓘ䋺60䌫䌭᷹ⷰ㑆㓒:1ಽObservationinterval: 1 min.
Time
until observation data transmission: 1 to 2 min.
᷹ⷰ䊂䊷䉺㈩ା䉁䈪䈱ᤨ㑆䋺1䌾2ಽ

Figure 1. Images of C Band Radar and X-MP Radar

3. Trial operation of X-MP radar
The River Bureau of the MLIT installed 11 X-MPradar bases in the three large metropolitan regions(Kanto, Chubu, Kinki, Hokuriku) in 2009, thenconducted trial transmissions beginning in July 2010.
The NILIM provided technical support for theintroduction of X-MP radar by, for example, building
the rainfall information transmission system.
Because the quality of radar observations is reducedby, for example, noise signals etc. received as a resultof mountains, buildings, and other obstructions in theobservation direction, to mitigate this problem, theNILIM set appropriate observation methods for X-MP
radar and adjusted patterns, improving the precisionand quality of rainfall observations. Considering thatguerrilla rainfall occurs unexpectedly, we also
constructed an integrated system able to rapidlycollect data from rainfall observations, process theinformation, and transmit it to a web site in order tomeet the challenge of real-time information provision. For these reasons, on the X-band MP radar rainfall
information web site published by the Ministry ofLand, Infrastructure, Transport and Tourism, users canview images of rainfall distribution occurring from 30
minutes earlier to the present moment (updated at 1
minute intervals). 
4. Future initiatives
Plans for X-MP radar installations in 2010 call for 4
bases in Chugoku, 5 in Kyushu, 3 in Chubu, 2 in
Tohoku, and 1 in Hokuriku. Beginning in 2011, trial
operations intended to improve observation precision
and advance torrential rainfall observations of a totalof 26 X-MP radar installations will begin, withfull-scale operation scheduled to begin in 2013. 
[X-band MP radar rainfall information web site] http://www.river.go.jp/xbandradar/

A Case of Utilizing Results(Key words) Guerilla rainfall, flood disaster, X-band MP radar