WIND FIELDS OF TYPHOON SONGDA (2004) OBSERVED BY THE OKINAWA DOPPLER RADAR (COBRA) Shinsuke Satoh *1 , Hiroko Nagahama 2 , Hiroshi Hanado 3 , and Katsuhiro Nak agawa 1 1 NICT Okinawa, Japan ([email protected]) 2 Tokyo Gakugei University, Japan 3 JAXA GPM DPR Project Team, Japan C-Band Okinawa Bistatic polarimetric RAdar (COBRA) < Specificatio ns > Frequency 5340 MHz Peak power 250 kW×2 (Klystron) 10 kW×2 (TWTA) COBRA+ Pulse width 0.5 / 1.0 / 2.0 s (Klystron) 0.5 - 100 s (TWTA) COBRA+ PRF 250-3000 Hz, PRT 1 s step staggered PRF Antenna 4.5 m parabola Antenna gain 45 dBi (inc. radome) Beam width 0.91 deg Sidelobe level < -30 dB (AZ dir., one way) < -28 dB (EL dir., one way) Cross pol ratio > 36 dB (integ in a beam) Tx Polarization H / V / +45 / -45 / LC / RC Doppler estimation Pulse-pair / FFT Range bin num > 2000 Antenna scan 0.5-10 rpm (PPI) 0.1-3.6 rpm (RHI) COBRA was installed on a mount ain peak (343 m in ASL + 15 m tower) in Nago city, Okinawa I sland. COBRA Observation Range and AWSs 0 1 2 3 4 5 6 7 8 9:00 12:00 15:00 18:00 21:00 0:00 3:00 M O TIO N [m /s] COBRA(± 30m in) COBRA(± 90m in) JM A BestTrack JST 0 10 20 30 40 50 60 -150 -100 -50 0 50 100 150 D IS T A N C E from the T yphoon C enter [km ] W IN D SPEED [m /s 915 925 935 945 955 965 975 PR ESSU R E [h P a 0224Z 0900Z 1403Z P =P c + Δ P exp[-(R m /R)^B] Δ P=62hPa,R m =47km ,B =1.1 Sea-LevelPressure M ax.Instant.W ind Speed M ean W ind Speed GradientW ind 1) Translate X-axis from time to distance using the typhoo n motion 2) Calculate a pressure regression curve using Holland’ eq uation (1980) 3) Calculate the gradient wind from the pressure gradient (and centrifugal force + Coriolis force) The distribution of the gradient wind is comparable to the distribution of the maximum instantaneous wind spee d except the radius of the maximum wind speed (calculat ed Rm=47 km, observed Rm=20 km). EL AZ PW PRF1 PRF2 Range Vm ax Integ Ant.Speed Time [deg] [deg] [us] [Hz] [Hz] [km ] [m /s] [hit] [rpm ] [sec] 1 +45 0.5 PPI 2.0 500.0 375.4 292.0 -21.14 32 1.1 54.5 VelFold 2 +45 0.9 PPI 2.0 500.0 375.4 292.0 -21.14 32 1.1 54.5 VelFold 3 +45 1.4 PPI 2.0 750.2 563.1 180.0 -31.68 32 1.3 46.2 VelFold 4 +45 2.0 PPI 2.0 750.2 563.1 170.0 -31.68 24 1.8 33.3 VelFold 5 +45 2.6 PPI 1.0 750.2 563.1 170.0 -31.68 24 1.8 33.3 VelFold 6 +45 3.4 PPI 1.0 750.2 563.1 170.0 -31.68 24 2.3 26.1 VelFold 7 +45 4.3 PPI 1.0 1000.0 750.2 140.0 -42.15 24 3.1 19.4 VelFold 8 +45 5.5 PPI 1.0 1000.0 750.2 140.0 -42.15 16 4.5 13.3 VelFold 9 +45 6.8 PPI 1.0 1000.0 750.2 140.0 -42.15 16 5.0 12.0 VelFold 10 +45 8.5 PPI 1.0 1000.0 750.2 140.0 -42.15 16 5.0 12.0 VelFold 11 +45 10.5 PPI 1.0 1350.4 1013.2 75.0 -56.94 16 6.0 10.0 VelFold 12 +45 13.0 PPI 1.0 1350.4 1013.2 75.0 -56.94 16 6.0 10.0 VelFold 13 +45 16.1 PPI 1.0 1350.4 1013.2 75.0 -56.94 16 6.0 10.0 VelFold 14 +45 20.0 PPI 1.0 1350.4 1013.2 75.0 -56.94 16 6.0 10.0 VelFold 17 +45 RHI 41.2 1.0 1000.0 - 100.0 14.04 64 0.5 30.0 EL=0° → 90° 20 +45 RHI 160.0 1.0 1000.0 - 100.0 14.04 64 -0.5 30.0 EL=90° → 0 22 +45 RHI 245.5 1.0 1000.0 - 100.0 14.04 64 -0.5 30.0 EL=0° → 90° 24 +45 RHI 340.0 1.0 1000.0 - 100.0 14.04 64 0.5 30.0 EL=90° → 0° No. Pol Note PW PRF Range Vm ax PW PRF Range [deg] [deg] TX [us] [Hz] [km ] [m /s] TX [us] [Hz] [km ] [hit] [rpm ] [sec] 1 +45 0.5 PPI 221 100.0 400.0 280.0 5.61 57 1.0 400.0 20.0 26 1.3 47.0 2 +45 0.9 PPI 221 100.0 400.0 280.0 5.61 57 1.0 400.0 20.0 26 1.3 47.0 3 +45 1.4 PPI 221 100.0 400.0 280.0 5.61 57 1.0 400.0 20.0 26 1.3 47.0 4 +45 2.0 PPI 221 100.0 400.0 250.0 5.61 57 1.0 400.0 20.0 18 1.8 34.0 5 +45 2.6 PPI 221 100.0 400.0 250.0 5.61 57 1.0 400.0 20.0 18 1.8 34.0 6 +45 3.4 PPI 221 100.0 400.0 250.0 5.61 57 1.0 400.0 20.0 16 2.0 30.0 7 +45 4.3 PPI 220 50.0 666.7 140.0 9.36 57 1.0 800.0 20.0 44 2.3 27.0 8 +45 5.5 PPI 220 50.0 666.7 140.0 9.36 57 1.0 800.0 20.0 36 3.0 20.0 9 +45 6.8 PPI 220 50.0 666.7 140.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 10 +45 8.5 PPI 220 50.0 666.7 140.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 11 +45 10.5 PPI 220 50.0 666.7 100.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 12 +45 13.0 PPI 220 50.0 666.7 100.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 13 +45 16.1 PPI 220 50.0 666.7 100.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 14 +45 20.0 PPI 220 50.0 666.7 100.0 9.36 57 1.0 800.0 20.0 26 4.1 15.0 17 +45 RHI 41.2 57 1.0 1000.0 100.0 14.04 57 1.0 1000.0 20.0 64 0.5 30.0 El=0→90 20 +45 RHI 160.0 57 1.0 1000.0 100.0 14.04 57 1.0 1000.0 20.0 64 -0.5 30.0 El=90→0 22 +45 RHI 245.5 57 1.0 1000.0 100.0 14.04 57 1.0 1000.0 20.0 64 -0.5 30.0 El=0→90 24 +45 RHI 340.0 57 1.0 1000.0 100.0 14.04 57 1.0 1000.0 20.0 64 0.5 30.0El=90→0 No. Pol 2nd Beam (ShortPulse) Pulse No. Pulse No. Note EL AZ Integ Ant.Spd Time 1stBeam (Long Pulse) COBRA+ (DualCycle Beam) COBRA (Dual-PRF) cos cos sin m r V V V Tangential comp. Radial Comp. Moving-speed Comp. : azimuth angle from the typhoon center to a measurement point : azimuth angle from the radar to the point : azimuth direction of the typhoon traveling motion cos sin sin sin cos cos cos sin sin cos m m r m m r d V V V V V V V V V o θ Tangential wind vector V Vd Doppler vel Typhoon traveling vector V m x y φ Vr Radial wind vector Coefficient of Tangential- wind component Coefficient of Radial- wind component Contribution rate of Tangential-wind comp 0 10 20 30 40 50 60 -150 -100 -50 0 50 100 150 D IS TA NC E from the T yphoon C enter [km ] W IN D SPEED [m /s 915 925 935 945 955 965 975 PR ESSU R E [h P a 0224Z 0900Z 1403Z P =P c + Δ P exp[-(R m /R)^B] Δ P=62hPa,R m =47km ,B =1.1 GradientW ind 0230Z-D oppler 0430Z-D oppler Sea-LevelPressure M ax.Instant.W ind Speed M ean W ind Speed 1230Z-D oppler - Estimated mean tangential-winds are consistent with the gradient wind (~ maximum instantaneous wind speed at surface) - The radius of maximum tangential-wind coincides with the eyewall echo radius •Typhoon SONGDA (2004) passed over the Okinawa main island, and was observed by COBRA for 18 hours. •The typhoon has an axial symmetry structure and a clear eyewall with a radius of 20 km. •A gradient wind calculated by the surface pressure gradient shows that the theoretical maximum wind speed is about 42 ms -1 . •The distribution of the mean tangential wind speeds estimated from the single Doppler radar (COBRA) data is consistent with the gradient wind and instantaneous maximum wind distribution. •The radius of maximum tangential-wind coincides with the eyewall echo radius. Summary 09/08,09JST 09/05, 09JST 09/08,12JST 09/05, 12JST 998hPa 27 28 29 30 31 01 02 03 04 05 06 07 980 975 945 935 935 945 935 940 940 945 08 970hPa 925hPa <Objectives of this study> To investigate the wind fields of typhoon SONGDA (T0418), which passed over the COBRA, using COBRA Doppler data, and surface observation data. Assumed tangential wind 0 10 20 30 40 50 60 70 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 台 台 台 台 台 台 台 台 台 [km ] 台 台 台 台 [m /s] Observed Raw Data Simulation (reference) Dual- PRF (pulse by pulse) Aliased vel corrected by using the continuity of Doppler vel 20 m/s Vmax=5.6 m/s 40 m/s 40 m/s Vmax=21.1 m/s 5 m/s Corrected Velocity Hopeless striped pattern 0 10 20 30 40 50 0 25 50 75 100 125 150 175 D ISTAN C E from the T yphoon C enter[km ] TA N G ENTIA L VEL [m /s] 0230Z 0330Z 0430Z 1230Z Observed Doppler velocity Subtract radial-vel (Vr=0) and traveling speed components Introduction Double eyewall echoes Radius of 20 km Estimated mean tangential velocities at 0230Z, 0430Z, and 1230Z Mean Tangential-wind and Surface-wind Estimation of Tangential-wind Distribution Correction of Aliased Doppler Velocity Moving Speed of the Typhoon Center Typhoon passed over the COBRA COBRA Observation Sequence Surface Meteor Data and Gradient Wind Outline of Typhoon SONGDA •A ground-based multi-parameter radar has the a dvantages of measuring the entire 3-dimensiona l structure and time evolution of a tropical c yclone, even though it has not mobility like a n airborne radar. •The COBRA has a function of arbitrary setting of the radar parameters to realize both long-r ange and large-velocity observation using an o ptimum PRF setting. •In this study, the distribution of the tangent ial wind in the typhoon Songda (2004) is revea led by the COBRA Doppler data, and it is evalu ated by comparisons with surface observation d ata. <COBRA Obs Data ~ 18 hours> 1030JST : dual-Cycle mode (TWTA pulse compre s) | 1800JST : Typhoon center passed over COBRA site | 1950-2120JST: Missing for 2 hours | 2230JST~ : dual-PRF mode (Klystron) | 9/6, 0430JST(1930Z)~: Missing by generator trouble Sequence every 10 min ・ PPI (14-EL angles) ・ RHI (4 AZ angles) ・ POS (EL=90 deg) Tx: +45 deg 、 Rx: H/V simultan ious Obs values: ZHH, ZVV, ZHV, Ve l, Wid, NCP, ZDR, (LD R), HV, DP 280 km Ishigaki Island Yonaguni Island Nago COBRA radar site Ogimi WPR site NICT Okinawa Center (Onna) < Data for analyses > - Ze + Doppler Vel (PPI EL= 0.9 deg) - AWS ground meteor data at COBRA site Range reso: 150 m/300 m Beam width: 0.9 deg