COBRA (CRL Okinawa Bistatic Polarimetric Radar) as a
Main Sensor of a Possible GPM Super Site in Okinawa
Shinsuke Satoh, Hiroshi Hanado, Katsuhiro Nakagawa, Tatsuhiro Adachi,
and Toshio Iguchi (Communications Research Laboratory, Tokyo, JAPAN)
Main characteristics of the COBRA
Concept of the GPM Super Site in Okinawa
GPM core satellite / DPR
Development / improvement of the dualfrequency precipitation radar algorithm
DSD profile estimation
using Doppler spectra
observed by the 400 MHz
wind profiler and 3D wind
fields observed by the
COBRA
Detection limit in 35GHz channel
Detection limit in 14GHz channel
Higher sensitivity at higher frequency
35GHz
radar
beam
14GHz
radar
beam
Discrimination between snow and rain
by attenuation difference
Height
Frequency
Peak power
Pulse width
PRF
Antenna
Antenna gain
Beam width
Sidelobe level
Cross pol ratio
Doppler estimation
Range bin num
Antenna scan
Bistatic
antennas
3D wind vectors (dual-Doppler)
14GHz
Ice
３５GHz
Accurate rain estimation based
on attenuation difference
SPIDER(95 GHz)
KLWC, FSSP,
2D-C, 2D-P probes
Radar Reflectivity Factor
+
Snow
Aircraft obs (G-II)
Doppler spectrum
(400 MHz Wind profiler)
Melting layer
Six kinds of polarization waves (H, V,
+45, -45, RC, and LC)
can be transmitted
pulse by pulse.
Rain
Microphysics observation
using aircrafts and multiparameter radars (multi-freq,
multi-polarization, Doppler)
1st proc. data: stokes parameters
and complex correlations
2nd proc. data:ZHH, ZVH, ZVV,ZHV,
ZDR, LDR, ρHV(0), φDP, KDP,
VEL, Spectrum-Wid, R(Z), R(KDP)
Data format: netCDF
Software: NCAR’s TITAN
Optical
rain gauge
Microwave
radiometer
Disdrometer
5340 MHz
250 kW ×2 (Dual Klystron)
0.5, 1.0, 2.0 µs
250-3000 Hz, 0.5 µs (PRT) step
4.5 m φ parabola in 8 m φ radome
45.6 dBi (H) / 45.7 dBi (V)
0.92 deg (H) / 0.91 deg (V)
< -30 dB (AZ), < -28 dB (EL)
> 36 dB (integ in a beam)
Pulse-pair / FFT
> 2000
0.5-10 rpm (PPI), 0.1-3.6 rpm (RHI),
0.1 rpm step, CW /CCW
CAMPR-G (14 GHz)
COBRA (5 GHz)
400 MHz Wind-profiler
1.3 GHz WP
OKINAWA Is.
Block diagram of the COBRA
Okinawa island is located in
200 km
the subtropics. There is much
rainfall with typhoon, Baiufront, extratropical cyclone,
and so on.
Bist #2 (Ogimi)
Antenna patterns of the COBRA main radar
Monthly mean rainfall in Okinawa (Naha)
Bist #1 (Onna)
250
35 km
COBRA bistatic dual-Doppler areas
Rainfall rate (mm)
COBRA Radar site
(26N 35’, 128E 04’)
1971∼2000
200
150
100
50
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
EL
[deg]
0.5
0.9
1.4
2.0
2.6
3.4
4.3
5.5
6.8
8.5
10.5
13.0
16.1
20.0
90.0
PW
[us]
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
1.0
0.5
PRF1 (Rmax, Vmax)
[Hz] ([km], [m/s])
750 (200.0, 10.5)
750 (200.0, 10.5)
750 (200.0, 10.5)
750 (200.0, 10.5)
750 (200.0, 10.5)
750 (200.0, 10.5)
811 (185.0, 11.4)
976 (153.7, 13.7)
1182 (126.9, 16.6)
1439 (104.2, 20.2)
1756 ( 85.4, 24.7)
2150 ( 69.8, 30.2)
2400 ( 62.5, 33.7)
2400 ( 62.5, 33.7)
2400 ( 62.5, 33.7)
PRF2 (Rmax, Vmax)
[Hz] ([km], [m/s])
563 (266.4, 7.9)
563 (266.4, 7.9)
563 (266.4, 7.9)
563 (266.4, 7.9)
563 (266.4, 7.9)
563 (266.4, 7.9)
608 (246.7, 8.5)
732 (204.9, 10.3)
887 (169.1, 12.5)
1079 (139.0, 15.2)
1317 (113.9, 18.5)
1613 ( 93.0, 22.7)
1800 ( 83.3, 25.3)
1800 ( 83.3, 25.3)
Unfold-Vmax
[m/s]
31.7
31.7
31.7
31.7
31.7
31.7
34.1
41.1
49.9
60.6
74.0
90.7
101.1
101.1
33.7
Integ
[hit]
64
64
64
64
64
64
64
64
64
64
64
64
64
64
1024
Ant.Spd
[rpm]
1.2
1.6
2.2
2.8
3.7
4.6
6.3
9.5
10.0
10.0
10.0
10.0
10.0
10.0
total= 292.1[sec]
Time
[sec]
54.
42.
33.
26.
21.
18.
15.
11.
11.
11.
11.
11.
11.
11.
6.
( 4m52s )
An example of the COBRA observation sequence optimized
by SROT (Sophisticated Radar Operation Technique).
___________________________________________________________
Examples of the COBRA observation data (2 km CAPPI and N-S vertical sections).
Corresponding author’s address: Shinsuke Satoh, Communications Research Laboratory,
4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan.
E-mail: satoh@crl.go.jp