[29] a N d N b 2 d sin θ N b ФФ a b Ф Ф θ θ a b Fig.1 Working principle demonstration of a phased-array antenna θ

1/(cos cos ) 1 X X <<>>20130576 863 2007AA061901 1988E mailliujun198802@126.com

[29] a N d N b 2 d sin θ N b ФФ a b Ф Ф θ θ a b Fig.1 Working principle demonstration of a phased-array antenna θ

B A B 1 2 A Fig.2 Schematic diagram of the X-band airborne weather radar system FFT/PPP X EEC X

S Table 1 Parameters of the X-band airborne phased array weather radar and X-band on-wheel weather radar of 724 th Institute kw kw db db mm mm ()() μsμs μs kmkmkmkm kmkm bd

a b (c) (d) e f

h i g k μs a μs c μs bd μs eh μs fi Fig.3 Measurement comparisons. (a) and (c) denote reflectivity factor measured with 6μs pulse or 1μs pulse width by X-band phased-array antenna weather radar(xpar).(e),(h) and (g) denote respectively reflectivity factor, radial velocity and spectrum width measured with 6μs pulse width by XPAR. (b) and (d) denote the smoothed reflectivity factor measured with 1μs pulse width by the 724 th Institute owned X-band weather radar(xrad). (f), (i) and (k) denote respectively reflectivity factor, radial velocity and spectrum width measured by XRAD. μs μsdoviak [34] Zrinc [35]

1μs 3 abcd μs a μs b μs c μs d abcd μsμs 50 45 6us Phased Array Radar 1us 724 Weather Radar 50 45 1us Phased Array Radar 1us 724 Weather Radar 40 40 Reflectivity/dBz 35 30 25 Reflectivity/dBz 35 30 25 20 20 15 15 10 10 0 15 30 45 60 0 15 30 45 60 75 Rang/Km Rang/Km b μs () μs ab Fig. 4 Radial velocity comparison for X-band phased array antenna radar (XPAR) and the 724 th Institute owned weather radar (XRAD). (a) Case of 6 μs pulse width for XPAR and 1μs pulse width for XRAD, (b) case of 1μs pulse width for XPAR and XRAD. μsμs kmdbz a μs km ab b μs cd

a bm/s m/s km km Table 2 Statistics result of radial reflectivity factor for XPAR and XRAD μs μs dbz μs μs μs μs μs dbz μs dbz μs μs dbzdbz μs μs μs μs 2 C(dB) 10lg[2.69 / (P t)] Gt Gr 160 L P t G t G r L C μs μs lgdb db μs db μs μs dbz dbz-7.8 dbdbz dbzdbz 1μs6μs S km km km, ( 3) Knorr, J.B 2 2 1024ln 2 LLR a Pr 2 1 ( ) 3 2 tg0 B0 B0c k 0 Z P coscos

L L R Pr a G 0 0 f 0 B0 B0 ( / 0 ) 1/cos cos 2 ( / 0 ) 1 db db μsμs db Table 3 Corrections for reflectivity factor of phased array antenna radar with angular shift to the normal direction of the panel efhi3.g3.k ac dbzm s -1 dbzm s -1 bd dbzm s -1 % ac X bd b dbz dbz dbz PAR gk ms -1 3.k

724 Weather Radar Z /dbz 50 45 40 35 30 25 20 15 10 5 Percentage / % 6 5 4 3 2 1 Phased Array Radar 724 Weather Radar 0 0 10 20 30 40 50 Phased Array Radar Z /dbz a 0 0 10 20 30 40 50 Reflectivity / dbz (b) 724 Weather Radar V /m.s-1 30 20 10 0-10 -20-30 -30-20 -10 0 10 20 30 Phased Array Radar V /m.s-1 (c) Percentage / % 22 20 18 16 14 12 10 8 6 4 2 Phased Array Radar 724 Weather Radar 0-30 -20-10 0 10 20 30 Velocity / m.s-1 (d) abc d Fig 5 Scatter plot of measurements by XPAR and XRAD at 10:39,3 rd August, 2012. (a) reflectivity factor. (b) percentage of reflectivity factor capturing (c) radial velocity (d) percentage of radial velocity capturing μsμs μs dbz μs lg dbdb dbz μs μs

1/cos cos X PRF X X

Comparative analysis of X-band phased array antenna weather radar measurements Liu Jun 1,2, Huang Xingyou 2, He Yuqin 2, Wang Zhenhui 2, Wang Jinhu 2 (1.Taizhou Meteorological Bureau,Taizhou,jiangsu 225300; 2.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, China, 210044) [Abstract]: Compared with the mechanical antenna weather-radar, the phased array antenna weather radar system has its special features of fast scanning and reliable data, which play an essential role in monitoring and warning meso-scale severe weather 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 1μs and 6μs pulse widths of the XPAR itself. The analysis based on comparisons shows (1) The measurements from XPAR with pulse width of 1us and 6us (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/(cos cos ) for correcting radar reflectivity factor. Key words: phased array weather radar; pulse compression; comparative analysis;data quality