jma’s c-band dual-polarization doppler weather radars …68... · jma’s c-band...
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WMO/CIMO/TECO-2016, Madrid, Spain, 27-29 September 2016 SESSION 2– Developments in observing technologies and system
JMA’s C-band dual-polarization Doppler weather radars with SSPAs
Naoki Tsukamoto1, Hiroshi Yamauchi1, Hidehiro Okumura2, Akihito Umehara1 and
Yusuke Kajiwara1
1 Japan Meteorological Agency (JMA), Tokyo, Japan
2 Narita Aviation Weather Service Center, JMA, Chiba, Japan
Abstract
In March 2016, the Japan Meteorological Agency (JMA) began to operate C-band
dual-polarization Doppler weather radars with solid-state power amplifiers (SSPAs) at
Kansai International Airport and Tokyo International Airport. The new radars feature a
dual-polarization function and SSPA pulse compression.
Observational data improvement is a major objective associated with the WMO
Integrated Global Observing System (WIGOS). The dual-polarization function is
expected to help improve quantitative precipitation estimation (QPE) and quality control
(QC), as well as to support the provision of new products that allow identification of
precipitation as rain, snow or hail. JMA is currently evaluating the accuracy of the new
radar observation based on comparison with surface observation data.
SSPA usage and the adoption of pulse compression reduce the radar’s peak power
from the 200 kW of conventional klystrons to just 10 kW. The set-up also supports
narrow bandwidth and improved signal detection capability, thereby contributing to the
mitigation of interference with 5 GHz-band radio LAN (RLAN).
The significant advantages of dual-polarization Doppler weather radar with SSPA will
be highlighted via analysis of observational data during the 2016 rainy season.
1. Introduction
In Japan, weather radar data are widely used for a variety of purposes including
weather monitoring/prediction, water resource management and aviation safety. Such
information therefore plays a pivotal role in protecting people from severe storms.
The Japan Meteorological Agency (JMA) deploys nine Doppler Radars for Airport
Weather (DRAWs) to support aviation safety. The first DRAW was installed at Kansai
International Airport in 1994, and has remained operational since then.
In 2016, the two DRAWs at Kansai International Airport and Tokyo International
Airport (Haneda) were replaced with new SP-DRAW (solid-state polarimetric DRAW)
types featuring SSPAs and dual polarization. Another SP-DRAW is scheduled for
installation at Narita International Airport in 2016.
The adoption of solid-state transmitters in DRAWs is based on the serious threat from
interference caused by telecommunication devices (e.g., RLAN) to weather radars
worldwide (Elena et al. 2015). The shortage of 5-GHz frequency band (C-band) space
allocated to weather radars and RLAN is also a problem in Japan.
To solve this problem, Japan’s radio regulatory authority is taking measures to
separate frequency bands allocated to weather radar and RLAN services. The resulting
radio frequency reallocation plan for weather radars in Japan will be based on nine
channels with increments of 5 MHz within narrow band-width areas, as opposed to the
conventional allocation plan based on channels with increments of 10 MHz. Accordingly,
there is a need to reduce the bandwidth, unwanted emissions and peak power of
weather radars.
During the period of transition from the conventional channel allocation plan to the
new reallocation plan, radio frequency channels may need to be temporarily changed
for some weather radars to prevent interference with other radars. However, changing
the transmission frequency of conventional radars requires very expensive waveguide
filters that allow high-power handling and very-narrow-band operation. In contrast, the
operation radio frequency of SP-DRAW can be readily changed because no such filter
is required.
To reduce operational costs, SP-DRAW also allows savings in areas such as
consumable parts (through factors such as elimination of the need to use magnetron or
klystron) and requires less space and electric power.
2. Characteristics of SP-DRAW
2.1 Purposes of SP-DRAW
Figure 1 shows the Haneda Airport SP-DRAW, whose main roles are to detect
low-level wind shear (LLWS, including microbursts (MB) and horizontal shear lines (SL))
at/around the airport and to alert pilots if threshold levels are exceeded (Fig. 2). Clutter
signals can reduce the quality of radar echo and consequently affect the reliability of
LLWS detection.
The SP-DRAW system can be used to identify weather and non-weather echoes using
dual-polarization parameters, while conventional Doppler weather radar data may be
affected by unintentional removal of weather echo because a high QC threshold is
adopted to reduce clutter contamination. The introduction of SP-DRAWs has enabled
the collection of high-quality Doppler velocity data without clutter contamination even in
weak echo regions, which improve accuracy for identification of areas of sudden wind
chan
aviat
nge. This ha
tion weathe
as led to bet
r radar usag
Fig
tter accurac
ge.
. 1 Haneda
Fig. 2 R
cy in LLWS
a Airport SP
Roles of SP
detection, w
P-DRAW to
P-DRAW
which is a m
ower
major purpoose of
2.2 Specifications of SP-DRAW and related operating parameters
Table 1 shows the specifications and operating parameters of SP-DRAW compared
with those of conventional DRAW.
Table 1. Specifications/operating parameters of SP-DRAW and conventional
DRAW
SP-DRAW Conventional DRAW
Frequency 5,360 MHz 5,280 MHz
Transmitters GaN Power FET Klystron
Peak transmitter power 5 kW for both H and V 200 kW
Antenna diameter 7 m (parabolic) 7 m
Beam width < 0.7° < 0.7°
Antenna gain > 47 dBi > 47 dBi
Signal min. < -110 dBm < -110 dBm
Side lobe level < -27 dB < -27 dB
Range side lobe level < -55 dB
Range gate spacing 150 m 150 m
Radome diameter 11 m 11 m
Antenna rotation rate 4.2 rpm (EL = < 9.2°) 4 rpm
7 rpm (EL > 9.2°)
Samples (hits) 18 – 29 32
Azimuth spacing 0.7° 0.7°
Pulse repetition frequency 1,040/832 Hz (EL = < 9.2°) 1,120/840 Hz
1,365/1,092 Hz (EL > 9.2°)
Pulse width 1 μs (range < 12 km) 1 μs
64 μs (range >= 12 km)
Transmission mode Dual (simultaneous) Single (horizontal)
Observation parameters Z, V, W, ZDR, ρHV, ΦDP Z, V, W
Transmission radio frequency can be set to any value between 5,330 and 5,370 MHz.
As high-power gallium nitride FETs are used for SSPAs, peak SP-DRAW transmitter
power can reach 5 kW for each (H/V) polarized wave. The bandwidth of transmitted
waves is quite narrow, and leakage to the adjacent channel is substantially suppressed.
Pulse widths can be set freely from 1 to 200 μs. JMA operationally uses values of 1
and 64 μs for short and long pulses, respectively. A pulse compression technique
invol
also
wave
obse
was
durin
Th
Th
detec
ZDR a
witho
evalu
can
obse
Du
rates
and h
Fo
of gr
clutte
ving the us
provides th
e transmiss
ervation mo
performed
ng the instal
he SP-DRAW
his 7-m ant
ction of LLW
and ρHV va
out radome
uation using
be set at
ervation time
ue to the tra
s differ betw
higher-eleva
or lower-elev
round clutte
er contamin
se of freque
he ability to
sion, which
de operatio
using a sta
llation perio
W parabolic
tenna allow
WS near the
alues, a cro
e; this has
g the metho
up to 7 rp
es.
ade-off betw
ween lower-
ation scans
vation scan
er removal
nation, the r
ency chirp
adjust the
is importa
on as repor
andard horn
od.
c antenna is
ws the gen
e surface. In
oss-polariza
been pro
od proposed
m for conf
ween the an
-elevation s
s (which are
ns, an anten
performanc
ate is set as
Fig. 3 S
is adopted
phase of d
ant for simu
rted by Hub
n antenna i
s shown in F
eration of
n addition,
ation isolatio
ven to exc
d by Frech e
iguration of
tenna rotat
scans (whic
e focused on
nna rotation
ce. For hig
s 7 rpm with
SP-DRAW a
in long-pu
drive signals
ultaneous t
bbert et al. (
n the far fie
Fig. 3.
sharp beam
to enable th
on value ex
ceed 34 d
et al. (2012
f optimal s
ion rate and
ch are more
n fast scann
n rate of 4.2
gher-elevatio
h high pulse
antenna
lse observa
s for horizo
transmissio
(2010). Rel
eld of SP-D
m patterns
he derivatio
xceeding 35
B with rad
). The ante
scan seque
d radar data
e easily affe
ning).
2 rpm is set
on scans w
e repetition
ation. SP-D
ontal and ve
n and rece
lated adjust
DRAW’s ant
appropriat
on of high-q
5 dB is sec
dome base
nna rotation
ncing to re
a quality, rot
ected by cl
in consider
with less gr
frequency.
DRAW
ertical
eption
tment
tenna
te for
uality
cured
ed on
n rate
educe
tation
utter)
ration
round
2.3 O
Th
minu
Dopp
meth
MB
(0.7°
The
plann
eleva
spare
is pe
struc
runw
prod
of sy
Th
Lo
the
Observatio
he major SP
ute and SL i
pler velocity
hod (Yamau
Bs are dete
°), while SLs
need to sc
ning scan
ation angle
e time for o
erformed to
ctures of pre
way. PPI sc
uces data u
ystem anom
hus, the five
ong pulse w
requisite s
n procedur
P-DRAW pr
identificatio
y data obta
uchi et al. 20
ected using
s are detec
can PPIs a
sequence
es and rang
observation
obtain RHI
ecipitation a
canning at
used for ca
malies, is con
e-minute sca
Fig. 4
width observ
sensitivity o
re
rocesses fo
n every five
ined using
006).
a plan pos
cted using P
at 0.7 and
for SP-DR
ge height
of precipita
I data, whic
and wind o
an elevatio
alibration of
nducted.
an sequenc
4 Five-minu
vation and p
of SP-DRA
or LLWS de
e minutes. T
the dual-PR
sition indica
PPIs at two
1.1° indivi
RAW. Mea
indicator (R
ation and wi
ch are espe
on the appro
on of 90° (
dual-polari
ce shown in
ute antenna
pulse-compr
AW, as the
tection invo
These forms
RF techniqu
tor (PPI) at
lower eleva
idually repr
nwhile, sca
RHI) opera
nd in and a
ecially usefu
oach to the
known as
zation para
Fig. 4 is im
a scan seq
ression tech
e peak tra
olve MB ide
s of detectio
ue and the
t the lowest
ation angle
resents a c
anning of
ation are co
around the a
ul for monito
e airport pa
bird-bath s
ameters and
mplemented
uence
hniques are
ansmitter p
entification e
on are base
hybrid mult
t elevation a
s (0.7 and
constraint i
PPIs at h
onducted d
airport. Sca
oring the ve
rallel to its
scanning), w
d early dete
for SP-DRA
e used to en
power for
every
ed on
ti-PRI
angle
1.1°).
n the
higher
during
nning
ertical
main
which
ection
AW.
nsure
each
polar
1-μs
corre
obse
short
1.5 t
and v
conv
As
marg
pract
mete
Fig.
Fig.
for c
rization is 5
pulse is
esponding
ervation, a
t-pulse obse
imes better
vertical ave
ventional rad
s the trunca
gin, a sensit
tical use b
eorological e
5 Relations
6 Relations
convention
5 kW (i.e., o
also use
to the tim
value of 6
ervation ran
r than that o
erage transm
dar, but its o
ated range f
tivity gap is
because sh
echoes nea
ship betwe
ship betwe
al DRAW (b
only 1/40th o
d to com
me of long
64 μs is a
nges (Fig. 6
of conventio
mitted powe
overall elec
for the long
observed a
hort pulses
ar the radar
een pulse w
een minimu
black line)
of those of
mplement o
g-pulse em
adopted for
6). As a res
onal DRAW
er from the n
ctricity consu
pulse widt
at 12 km. Ho
s (1 μs) h
site (Fig. 7)
width and m
um detecta
and SP-DR
convention
observation
mission (Fig
r better sen
ult, the ave
(1 μs, 200
new radar s
umption is 2
h (64 μs) is
owever, this
ave enoug
).
measurable
able reflecti
RAW (purp
al radars w
within tru
g. 5). In
nsitivity bo
rage power
kW). The o
system is th
20 percent l
s equal to 1
s does not p
gh power f
e area
ivity and ra
le line)
with a klystro
uncated ra
long-pulse-
th in long-
r of SP-DRA
overall horiz
hree times th
lower.
2 km with s
pose proble
for detectio
ange from r
on). A
anges
-width
- and
AW is
zontal
hat of
some
ms in
on of
radar
Fig.
at an
obse
2.4 Im
Th
Figur
and s
Th
inform
polar
synth
malfu
reduc
Tw
Thes
The
data
dual
Tw
As
syste
syste
and r
7 PPI plots
n elevation
ervation re
mproveme
he transmitte
re 9 gives
signal proce
he SP-DRAW
mation to f
rized waves
hesized fro
unction, ope
ced transm
wo receiver/
se devices
active syste
processors
system.
wo antenna
s SP-DRAW
em stability
em status in
receiver sen
s of (a) refle
n angle of
gion.
ent of radar
er, receiver,
an overview
essor.
W system is
flights. The
s and anoth
om the out
eration can
ission powe
/signal proc
are used to
em of the d
s used to co
controllers
W is premise
checking a
n daily app
nsitivity usin
ectivity and
f 1.1°. The
r system st
, signal proc
w of the sy
s designed w
transmitte
her eight fo
put of thes
be continu
er.
cessor sets
o generate
devices outp
onduct LLW
are operate
ed on conti
and quality
plication, SP
ng test sign
d (b) Doppl
blue dott
tability
cessor and
ystem includ
with high re
r consists o
or vertical p
se sixteen
ed on the b
s are opera
drive signa
puts observ
WS detectio
ed in the for
nuous syst
maintenanc
P-DRAW co
nals.
ler velocity
ted circle
antenna co
ding the an
edundancy t
of eight SS
polarized w
modules.
basis of rad
ated in the
als and rec
vation data
n, which ar
rm of a dup
tem operatio
ce in day-to
onstantly m
y for weak w
indicates t
ontroller are
ntenna, tran
to ensure st
SPA module
aves, and
In the eve
ar equation
form of a
ceive/proces
(the mome
re operated
lex system.
on, it includ
o-day opera
onitors tran
weather ec
the short-p
e shown in F
nsmitter, rec
table provis
es for horiz
transmits w
ent of a mo
n calculation
duplex sys
ss echo sig
nt data) into
in the form
.
des function
ation. To mo
nsmission p
choes
pulse
Fig. 8.
ceiver
ion of
zontal
waves
odule
n with
stem.
gnals.
o two
m of a
ns for
onitor
power
As m
enab
mentioned p
ble detection
Fig. 8 Tr
previously, S
n of system
ransmitter,
SP-DRAW m
m errors and
receiver, s
monitors ZD
misalignme
signal proc
DR and ΦDP
ents across
cessor and
using bird-b
s the whole
antenna c
bath scanni
system.
controller
ing to
2.5 Q
To
are e
algor
movi
data
used
no ef
used
also
proce
proce
Fig
dual-
align
Quality con
improve th
essential fo
rithm for wh
ing clutter s
and cause
d for conven
ffect in rela
d to efficient
results in th
essing data
essing data
gure 10 sh
-polarization
ment (CPA
F
ntrol metho
he quality o
or LLWS de
hich dual-po
such as sh
e false LLW
ntional Dopp
ation to mov
tly distingui
he removal
a should b
a (NOR) sho
hows a flo
n paramete
A; Hubbert e
Fig. 9 Block
ods
of Doppler v
tection, SP
olarization
ips and win
WS detectio
pler radars
ving clutter.
sh both GC
or attenuat
e applied o
ould be app
ow chart of
ers are use
et al. 2009)
k diagram o
velocity data
-DRAW inc
parameters
nd turbines
on. Although
help to mitig
Meanwhile
C and movin
ion of weat
only for bin
plied for pure
f the clutte
ed. This inv
and the tex
of SP-DRAW
a at the low
corporates a
s are utilize
impair the
h the movi
gate GC to
e, dual-pola
ng clutter. T
her echo. T
ns contami
e weather e
er discrimin
volves the
xture of the
W
west elevat
a new clutte
d. Ground
quality of
ng target in
a certain de
arization par
The use of M
To avoid this
nated by G
echo.
nation algo
utilization
differential
ion angle, w
er discrimin
clutter (GC
Doppler ve
ndicators (M
egree, they
rameters ca
MTIs some
s side effect
GC, and no
orithm for w
of clutter p
phase S(Φ
which
nation
) and
elocity
MTIs)
have
an be
times
t, MTI
ormal
which
phase
ΦDP) in
addit
to de
error
for p
proce
If th
thres
CPA(
assu
MTI
or m
MTI d
The
for o
3. SP
As
preci
comp
obse
evalu
the T
July
tion to the c
etermine w
r (RMSE) of
recipitation
essing data
he CSR, CP
sholds, the
(MTI) and S
med to be c
[flag 1]. Oth
oving clutte
data and in
threshold v
ptimization
P-DRAW ob
s part of pola
ipitation es
parison with
ervation site
uation for a
Tateno surfa
2016. Figur
conventiona
hether indiv
f fitting for Φ
echo and la
a and MTI p
PA(NOR) a
bin is assu
S(ΦDP)(MTI
contaminate
herwise, the
er whose ef
valid data a
values can b
to avoid sig
Fig.
bservation
arimetric pe
stimates u
h data from
es around e
heavy rainf
ace observ
re 11 shows
al clutter sup
vidual bins
ΦDP values o
arge for clu
rocessing d
and S(ΦDP)(
umed to be
) values fo
ed by weak
e bin is assu
ffects are d
are applied
be adjusted
gnificant effe
10 Clutter
data
erformance
sing SP-D
weighing ra
ach SP-DR
fall event th
ation site 6
s PPIs of re
ppression ra
include clu
of five bins
utter. CPA an
data.
NOR) value
e uncontam
r the bin ar
ground clu
umed to be
difficult to m
for bins flag
, and JMA
ects on wea
discrimina
verification
DRAW dua
ain gauges
RAW. This s
at produced
65 km north
eflectivity Z
ate (CSR) d
utter. S(ΦDP
in a radial r
nd S(ΦDP) a
es for a ce
minated by c
re below th
tter whose e
contaminat
mitigate with
gged with [0
is currently
ather echo.
ation algor
, the JMA is
al-polarizatio
(WGs) inst
ection deta
d hourly pre
heast of the
and the spe
derived from
P) is the ro
row. The pa
are calculat
ertain bin ar
clutter [flag
e set thres
effects are w
ted by stron
h MTI [flag
0], [1] and [2
evaluating
rithm
s evaluating
on parame
talled at five
ils the prelim
ecipitation o
e Haneda S
ecific differe
m MTI proce
ot mean sq
arameter is
ed for both
re below th
g 0]. If the
sholds, the
well mitigat
ng ground c
2]. Normal
2], respectiv
the values
g the accura
eters based
e special su
minary resu
of up to 57 m
SP-DRAW o
ential phase
essing
quare
small
NOR
he set
CSR,
bin is
ed by
clutter
data,
vely.
used
acy of
d on
urface
ults of
mm at
on 14
e Kdp
as o
(2012
(200
reflec
(a) a
respe
Fig
weig
cons
grou
desc
seen
cumu
R(W
Fig.
DRA
cros
Tate
bserved via
2), which in
1), the rain
ctivity Z_co
and (b) sh
ectively. Th
gure 13 sh
hing rain g
sideration of
nd, the tim
cent rate of
n, R(Z) rep
ulative valu
G), while th
11 PPI plo
AW with an
sses and w
no site, res
a the Hane
nvolves the
rate R(Kdp
orr. Convent
how distribu
e latter sho
hows a tim
gauge data
f the time ta
es of R(Z)
4 m/s. Wh
presents sig
e of R(Kdp
hat of R(Z) is
ots of (a) r
n elevation
white circle
spectively.
eda SP-DR
e use of co
p, Z_corr) i
tional rain ra
utions of e
ows heavy ra
me-series re
a R(WG), R
aken for ra
and R(Kdp
hile corresp
gnificant u
, Z_corr) fro
s 74% unde
reflectivity
n angle of
es indicate
RAW. In line
oefficients p
s estimated
ate estimat
estimated r
ain areas m
epresentati
R(Z) and R
indrops to f
p, Z_corr) a
pondence b
nderestima
om 16:57 to
erestimated
and (b) K
0.7º at 171
e the locat
e with the m
proposed by
d using Kdp
ion R(Z) is
rain rates
more clearly
on of rain
R(Kdp, Z_c
fall from a d
are delayed
etween R(K
ation of the
o 17:57 is 1
d.
Kdp as obs
10 JST on
ions of the
method of
y Bringi an
p and atten
also condu
R(Z) and
.
rates as
corr) at the
distance of
d by 4 minu
Kdp, Z_corr
e rain rate
1% undere
served usi
14 July 2
e Haneda
Yamauchi
d Chandras
uation-corre
cted. Figure
R(Kdp, Z_
observed
Tateno sit
1 km abov
utes assum
r) and R(W
. The one
stimated ag
ng the Ha
2016. The b
DRAW and
et al.
sekar
ected
es 12
_corr),
using
te. In
ve the
ming a
WG) is
e-hour
gainst
aneda
black
d the
Fig.
(b) R
Fig.
gaug
Z_co
4. Su
SP
anten
obse
In
assu
conti
12 As per
R(Kdp, Z_co
13 Time-s
ges (thin g
orr) (thick r
ummary an
P-DRAW gu
nna scann
ervational ca
response t
rance sys
inuous qua
Fig. 11, bu
orr)
series repr
green line)
red line)
nd future pl
uarantees a
ning. The
apacity for p
to growing
tem now
ality monito
ut with rain
resentation
and estim
lans
dequate rad
results of
practical op
demand fo
includes a
ring based
rate distri
n of rain ra
ated using
dar observa
the study
eration in v
or high-qua
a built-in
on bird-ba
ibution est
ates obser
g R(Z) (dot
ation data q
y confirme
very strong t
ality radar d
independen
ath scannin
timated usi
rved using
ted blue li
quality even
ed the exp
to very wea
data, the S
nt checking
ng to detec
ing (a) R(Z)
g weighing
ne) and R(
with high-s
pected lev
ak echo area
P-DRAW q
g function
ct issues d
) and
g rain
(Kdp,
speed
el of
as.
uality
and
during
operation.
High-quality data and frequent observation are essential for the early detection of
severe storms, which is one of JMA’s goals.
In relation to effective radio frequency usage, solid-state transmitters are very useful
because they support:
- achievement of balance between peak power reduction and high data quality;
- mitigation of unexpected emissions against adjacent channels; and
- simple frequency changes.
With this approach, electricity consumption is 20% less than with conventional radar.
Observational data improvement is a major objective associated with the WMO
Integrated Global Observing System (WIGOS). To support the achievement of this goal,
JMA will share lessons learned from its adoption of new-generation weather radars with
NMHSs.
References
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