34 4 2015 8 PLATEAU METEOROLOGY Vol. 34 No. 4 August 2015. X J. 2015 34 4 1167-1176 doi 10. 7522 /j. issn. 1000-0534. 2014. 00043. X / 210044 X X X X 6 μs 1 μs 1 6 μs μs X 2 3 1 / cosθcosφ 1000-0534 2015 04-1167 - 10 doi 10. 7522 /j. issn. 1000-0534. 2014. 00043 P412. 25 A 1 90 1-8 10 11-6 min 28 X 6 min X 9 2. 1 20 60 29 1 40 1a N 2 2013-12 - 16 2014-03 - 18 863 2007AA061901 1988. E-mail liujun198802@ 126. com
1168 34 Fig. 1 1 a 0 b 90 - Φ Working principle demonstration of a phased-array antenna. a Scanning angle is 0 b scanning angles are 90 - Φ d 1a N 1b θ θ = 2πdsin N λ 1b Ф Ф 1a 0 1b 90 - Ф Ф θ θ 2 X Fig. 2 Schematic diagram of the X - band airborne θ 360 0 ~ 360 2. 2 weather radar system X 2
4 X 1169 14 18 A /D 31 FFT /PPP 32 CINRAD - SA S 3 3. 1 3. 2 2012 6 8 X 724 724 724 30 m EEC X 6 7 724 2. 27 m 8 9 10 3. 6 m 4. 7 m 199. 34 197. 82 198. 04 0. 94-0. 55 30 3 724 PPI Table 1 1 724 Parameters of the X - band airborne phased array weather radar XPAR and X - band on-wheel weather radar of 724 th Institute XRAD 724 / ± 60 360 /kw < 10 75 / db < 40 40 /m 75 150 150 300 / /μs 3. 6 2. 4 1. 4 1 6 1 /km 75 120 150 240 75 150
1170 34 6 μs 1 μs 4 6 μs 1 μs 4a 2 33 1 52 km 724 724 724 3a b 4b 2 4 3c d 4. 1 724 6 μs 1 μs Doviak et al 34 35 32 36 4a 4b - 15 ~ - 6 m s - 1 15 ~ 45 km 724 724 1 μs 2 3a ~ d 2012 7 1 15 30 2 724 15 46 Table 2 Statistics result of radial reflectivity factor 6 μs 3a for XPAR and XRAD 724 1 μs 3b 1 μs 3c 724 1 /dbz 1. 30 6. 90 μs 3d /dbz 4. 60 2. 90 202 198 3a ~ d 0. 85 0. 83
4 X 1171 3 Fig. 3 2012 7 1 15 30 a b 15 46 c d 724 dbz a 6 μs b c d 1 μs Comparisons of the reflectivity factor measured by X - band phased array antenna radar left and the smoothed 724 th Institute owned weather radar right at 15 30 a b and 15 46 c d on 1 July 2012. Unit dbz. a 6 μs pulse b c and d 1μs pulse 4 6 μs a 1 μs b 1 μs 724 Fig. 4 Radial velocity comparison for measured with 6 μs a and 1μs b pulse width of XPAR with 1μs pulse width of XRAD 2 6 μs 724 1 dbz 1 μs 6 μs 1 μs 724 7 dbz 1 μs 6 μs 6 μs 1 μs
1172 34 1 < 1 dbz 7 dbz 1 μs 3. 6 2. 4 100 km 6 μs - 78. 5 7 km 5 km 1 μs 6 3 μs Knorr 38 37 C = 10lg 2. 69 λ 2 / P t τθ - G t - G r + 160 + L ε 1 λ P t G t G r τ 2 θ P L ε r L a L C τ 1 μs ε R G 6 μs 10lg6 db 0 λ 0 f 0 θ 7. 8 db 1 μs B0 φ B0 0 7. 8 db 1 λ /λ μs 6 μs 0 1 / cosθcosφ 0. 9 dbz 6. 90 dbz - 7. 8 db 1. 3 dbz θ φ Z = 1024ln2 L L ε ar 2 λ 2 P r P t G 0 θ B0 φ B0 cτπ 3 k 2 λ /λ 0 2 1 3 0. 9 dbz 3 1. 3 dbz 1 μs 6 μs < 15 4. 2 < 0. 5 db S ( ) λ λ 0 2 1 cosθcosφ Table 3 3 Corrections for reflectivity factor of phased array antenna radar with angular shift to the normal direction of the panel 0 8 16 32 40 48 56 0 0 0. 042 0. 172 0. 715 1. 157 1. 745 2. 524 8 0. 042 0. 085 0. 214 0. 758 1. 200 1. 787 2. 567 16 0. 172 0. 214 0. 343 0. 887 1. 329 1. 916 2. 696 32 0. 715 0. 758 0. 887 1. 432 1. 873 2. 461 3. 240 40 1. 157 1. 200 1. 329 1. 873 2. 315 2. 902 3. 682 48 1. 745 1. 787 1. 916 2. 461 2. 902 3. 490 4. 269 56 2. 524 2. 567 2. 696 3. 240 3. 682 4. 269 5. 049 db
4 X 1173 5 Fig. 5 2012 8 3 10 39 6 μs a c e 1 μs 724 b d f a b c d e f Comparisons of reflectivity factor a b radial velocity c d and spectrum width e f measured with 6 μs pulse width by X - band phased array antenna radar a c e and 1 μs pulse width by the 724th Institute owned weather radar b d f at 10 39 on 3 August 2012 9. 5 /15 6b d ± 60 ± 38 3 40 2 db 4 1 μs 6 μs 5b < 13 dbz 724 13 ~ 22 dbz 724 4. 3 14 PAR 5e f 724 3 ~ 5 m s - 1 5f 724 2012 8 3 10 39 5 6 5 6a c 2012 6-8 1 X 1 6 μs 1 μs
1174 34 6 Fig. 6 2012 8 3 10 39 a b c d Distribution of measurements reflectivity factor a percentage of reflectivity factor capturing b radial velocity c and percentage of radial velocity capturing d by XPAR and XRAD at 10 39 on 3 August 2012 6 μs 0. 85 1. 3 dbz 1 μs 0. 83 10lg 6 db 7. 8 db 0. 9 dbz 4 1 / cosθcosφ 2 X PRF 6 μs 1 μs 3 39
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1176 34 Comparative Analysis of X - Band Phased Array Antenna Weather Radar Measurements LIU Jun HUANG Xingyou HE Yuqin WANG Zhenhui WANG Jinhu Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science & Technology Nanjing 210044 China Abstract Compared with the mechanical antenna weather-radar phased array antenna w eather radar system has its special features of fast scanning and reliable data which play an essential role in monitoring and warning meso - scale severe w eather system. The parameters and characteristics of the X - band phased array antenna radar system XPAR as well as its activities in surface-based field campaigns are introduced. Measurements by XPAR and X - band mechanical antenna radar XRAD are compared including the measurement difference between 1 μs and 6 μs pulse widths of the XPAR itself. The analysis based on comparisons shows 1 The measurements from XPAR with pulse width of 1 μs and 6 μs pulse compression mode are close to the measurements from XRAD XPAR with pulse compression mode has even better data quality and good echo image particularly at distant region. 2 Due to the broad beam width the XPAR reflectivity factor is smooth the weak echo area decreases and strong echo area increases. 3 The non - uniform antenna gain of XPAR has influence on data quality but can be theoretically compensated by a gain factor of 1 / cosθcosφ for correcting radar reflectivity factor. Key words Phased array weather radar Pulse compression Comparative analysis Data quality