A Case of Utilizing Results

Technical matters for introduction of X-band MP
Radar observation
KAWASAKI Masao(Ph.D., Engineering), HeadTSUCHIYA Shuichi, ResearcherWater Management and Dam Division, River Department(keywords) XRAIN, X-band MP Radar, heavy rain observation, technical data
1.

Introduction
In recent years, scattered heavy rain and localized
heavy rain frequently occur all over Japan and theygenerated flood damages and water accidents. It is
important to understand the heavy rain situation
accurately for disaster control measures and weather
radars which can receive real time precipitation
information in the whole area are highly effective.
Water and Disaster Management Bureau of Ministry ofLand, Infrastructure, Transport and Tourism have
deployed X-band MP (multi parameter) Radars, therecent model weather radars, and have built a radarobservation network called XRAIN intending to enhance
image resolution of radar precipitation information and toimprove real time processing, thereby enhancing heavy
rain observation system and high precision of flood
forecasting are underway. XRAIN started its trial
operations in 2010 with a network of 11 radars andadditional radars were deployed every year thereafter. Asof now (2012) a network of 27 radars is implementing
trial operations.
2.

Establishment of technical matters to introduce
X-band MP Radar observation
Radars are the equipment to transmit radio waves andreceive the radio waves reflected from precipitation
particles group and they do not directly measure theprecipitation. The data directly obtained from radars are
the strength of radio waves propagated through andreflected from the precipitation particles group and thephase information. Rainfall observation by radars utilizes
the characteristics that such information is relevant to theintensity of rainfalls of precipitation particles group. In
order to observe precipitation with high precision byradars, it is required to study scan mode such as theelevation angle of antennas and the rotation speed and toconduct the identification operation of calculation
parameters of the precipitation and so forth. Manufacture
and installation of radars only never achieves
precipitation observation with high precision.
There is no precedent in the world to put X-band MP
Radars to practical use.
Therefore, NILIM, inintroducing them, in cooperation with experts of radarobservation, have been conducting studies on design ofradar network, building of data processing and delivery
system, scan mode and parameter tuning, etc. and also,enhancement of decay compensation and synthesis
method. Thus we have been contributing to securementof the specified accuracy of X-band MP Radarobservation, to improvement of the accuracy and toestablishment of technical matters.
3. Preparation of technical data
Three years have passed since the construction of
XRAIN and it is scheduled to proceed to an official
operation from the trial operations. Accordingly, thetechnical data which summarized technical knowledge
obtained through the trial operations and assembled theinformation about observation system by X-band MP
Radar, calculation method of precipitation and various
study methods were prepared this time.
The first half of the technical data describes theprinciple specifications of radars, transmission method,signal processing, system structure of XRAIN andcalculation method of rainfall intensity as matters related
to hardware and software composing XRAIN. The
latter half describes selection of radar installation
locations, ideas about observation configuration, initialadjustments, various verifications and study methods asmatters related to introduction of X-band MP Radars andinitial adjustments and verifications.
The technical data are scheduled to be published as
NILIM papers. It is expected that the data will be ofsome help toward technical development concerning
future introduction of radars by Regional Development
Bureaus and local governments, radar observation andutilization of radar precipitation information.
Moreover, in the future, depending on the progress of
research and development of technology, specificationsof equipment to be employed by XRAIN andprecipitation calculation methods, etc. will possibly beamended and improved and on this occasion, thetechnical data will be revised accordingly.