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Clutter (radar)

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152:, and can cause serious performance issues with radar systems. What one person considers to be unwanted clutter, another may consider to be a wanted target. However, targets usually refer to point scatterers and clutter to extended scatterers (covering many range, angle, and Doppler cells). The clutter may fill a volume (such as rain) or be confined to a surface (like land). A knowledge of the volume or surface area illuminated is required to estimated the echo per unit volume, η, or echo per unit surface area, σ° (the 1736:
level to a height of 1750 metres. There could be rain at ground level but the top of the beam could be above cloud level. In the part of the beam containing rain the rainfall rate will not be constant. One would need to know how the rain was distributed to make any accurate assessment of the clutter and the signal to clutter ratio. All that can be expected from the equation is an estimate to the nearest 5 or 10 dB.
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For a target close to the Earth's surface such that the earth and target are in the same range resolution cell one of two conditions are possible. The most common case is when the beam intersects the surface at such an angle that the area illuminated at any one time is only a fraction of the surface
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The implication is that when the radar is noise limited the variation of signal to noise ratio is an inverse fourth power. Halving the distance will cause the signal to noise ratio to increase (improve) by a factor of 16. When the radar is volume clutter limited, however, the variation is an inverse
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The general significant problem is that the backscatter coefficient cannot in general be calculated and must be measured. The problem is the validity of measurements taken in one location under one set of conditions being used for a different location under different conditions. Various empirical
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A problem with volume clutter, e.g. rain, is that the volume illuminated may not be completely filled, in which case the fraction filled must be known, and the scatterers may not be uniformly distributed. Consider a beam 10° in elevation. At a range of 10 km the beam could cover from ground
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The surface clutter return depends upon the nature of the surface, its roughness, the grazing angle (angle the beam makes with the surface), the frequency and the polarisation. The reflected signal is the phasor sum of a large number of individual returns from a variety of sources, some of them
260:. The total signal competing with the target return is thus clutter plus noise. In practice there is often either no clutter or clutter dominates and the noise can be ignored. In the first case, the radar is said to be noise-limited, while in the second it is clutter-limited. 1121: 2466: 2293: 1745:
capable of movement (leaves, rain drops, ripples) and some of them stationary (pylons, buildings, tree trunks). Individual samples of clutter vary from one resolution cell to another (spatial variation) and vary with time for a given cell (temporal variation).
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There are a number of problems in calculating the signal to clutter ratio. The clutter in the main beam is extended over a range of grazing angles and the backscatter coefficient depends upon grazing angle. Clutter will appear in the
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If the Clutter Return Power is greater than the System Noise Power then the Radar is clutter limited and the Signal to Clutter Ratio must be equal to or greater than the Minimum Signal to Noise Ratio for the target to be detectable.
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For the pulse length limited case the area illuminated depends upon the azimuth width of the beam and the length of the pulse, measured along the surface. The illuminated patch has a width in azimuth of
1962: 1187: 1622: 1245: 2909: 2649:{\displaystyle \ {\frac {S}{C}}={\frac {1}{1300}}{\frac {R^{3}}{P_{t}G^{2}\lambda ^{2}}}{\frac {1}{\tau \theta \sec \psi \sigma ^{o}}}{\frac {P_{t}G^{2}\lambda ^{2}}{(4\pi )^{3}R^{4}}}\sigma } 2029: 2846: 964: 640:
The clutter is assumed to be a large number of independent scatterers that fill the cell containing the target uniformly. The clutter return from the volume is calculated as for the normal
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and that the scatterers are uniformly distributed through the volume. The clutter volume illuminated by a pulse can be calculated from the beam widths and the pulse duration, Figure 1. If
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A correction must be made to allow for the fact that the illumination of the clutter is not uniform across the beamwidth. In practice the beam shape will approximate to a
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In the case of surface clutter the signal to clutter now varies inversely with R. Halving the distance only causes a doubling of the ratio (a factor of two improvement).
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Clearly narrow beamwidths and short pulses are required to reduce the effect of clutter by reducing the volume of the clutter cell. If
240:). This clutter type is especially bothersome since it appears to move and behave like common targets of interest, such as aircraft or 1727:
is used then the appropriate pulse duration to be used in the calculation is that of the compressed pulse, not the transmitted pulse.
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The tradeoff for doing this is that adding fill pulses will degrade the performance, due to wasted transmitter power and a longer
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First find the magnitude of the clutter return. Assume that the clutter fills the cell containing the target, that scatterers are
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is the time duration of the transmitted pulse then the pulse returning from a target is equivalent to a physical extent of
1579: 1202: 153: 61: 1116:{\displaystyle \ C={\frac {P_{t}G_{t}A_{r}}{2\log 2(4\pi )^{2}R^{4}}}{\frac {\pi }{4}}(R\theta )(R\phi )(c\tau /2)\eta } 145: 2857: 2288:{\displaystyle \ C={\frac {c}{2^{7}\pi ^{3}}}{\frac {P_{t}G^{2}\lambda ^{2}}{R^{3}}}\tau \theta \sec \psi \sigma ^{o}} 1973: 2788: 68: 3864: 164:
Clutter may be caused by man-made objects such as buildings and — intentionally — by radar countermeasures such as
3814: 35: 2751:{\displaystyle \ {\frac {S}{C}}=4\times 10^{-7}{\frac {\cos \psi }{R\tau \theta }}{\frac {\sigma }{\sigma ^{o}}}} 814:{\displaystyle \ C={\frac {P_{t}G_{t}A_{r}}{(4\pi )^{2}R^{4}}}{\frac {\pi }{4}}(R\theta )(R\phi )(c\tau /2)\eta } 354:, as is the return from any individual element of the clutter. The azimuth and elevation beamwidths, at a range 304: 3863:
systems. Clutter folding becomes a problem when the range extent of the clutter (seen by the radar) exceeds the
75: 3772:{\displaystyle \ {\frac {S}{C}}=5.25\times 10^{4}{\frac {1}{\theta ^{o2}R^{2}}}{\frac {\sigma }{\sigma ^{o}}}} 1126:
A number of simplifying substitutions can be made. The receiving antenna aperture is related to its gain by:
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formulae and graphs exist which enable an estimate to be made but the results need to be used with caution.
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The same antenna is generally used both for transmission and reception thus the received clutter power is:
277: 217: 165: 57: 3868: 3182:{\displaystyle \ C={\frac {P_{t}G^{2}\lambda ^{2}}{(4\pi )^{3}R^{4}}}\pi R^{2}(\theta /2)^{2}\sigma ^{o}} 2774:, which again will involve a range of grazing angles and may even involve clutter of a different nature. 4104: 3905:"Detection of Ground Clutter for Dual-Polarization Weather Radar Using a Novel 3D Discriminant Function" 1777: 237: 2771: 4024: 3961: 3916: 188:
trails. Radar clutter can also be caused by other atmospheric phenomena, such as disturbances in the
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square law and halving the distance will cause the signal to clutter to improve by only 4 times.
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to detect targets. Clutter may also originate from multipath echoes from valid targets caused by
3455:{\displaystyle \ C={\frac {P_{t}G^{2}\lambda ^{2}}{4^{4}R^{2}}}(\theta ^{o}/180)^{2}\sigma ^{o}} 3950:"Detection of Ground Clutter from Weather Radar Using a Dual-Polarization and Dual-Scan Method" 377: 252:
Electromagnetic signals processed by a radar receiver consist of three main components: useful
3303:{\displaystyle \ C={\frac {P_{t}G^{2}\lambda ^{2}}{4^{4}\pi ^{2}R^{2}}}\theta ^{2}\sigma ^{o}} 1724: 1713:{\displaystyle \ {\frac {S}{C}}={\frac {16(\log 2)\sigma }{\pi R^{2}\theta \phi c\tau \eta }}} 951: 193: 3317: 2329: 405: 4077: 3969: 3924: 3879:
of the radar, increasing the range over which clutter suppression is applied by the system.
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As in the case of Volume Clutter the Signal to clutter ratio follows an inverse square law.
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The expression for the target return remains unchanged thus the signal to clutter ratio is
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The calculation is similar to the previous examples, in this case the illuminated area is
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respectively if the illuminated cell is assumed to have an elliptical cross section.
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is the unwanted return (echoes) in electronic systems, particularly in reference to
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are examples of volume clutter. For example, suppose an airborne target, at range
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the Gaussian approximation of the antenna. The corrected back scattered power is
3803: 300:, is within a rainstorm. What is the effect on the detectability of the target? 24: 4059: 4028: 121: 4073: 3929: 3904: 3872: 1753: 1340:{\displaystyle \ C={\frac {P_{t}G\lambda ^{2}}{1024(\log 2)R^{2}}}c\tau \eta } 955: 233: 205: 189: 177: 173: 149: 1450:{\displaystyle \ S={\frac {P_{t}G^{2}\lambda ^{2}}{(4\pi )^{3}R^{4}}}\sigma } 4036:(Technical report). RADC Technical Reports. Vol. 1980. Rome, New York: 668:, and the clutter cell volume as derived above. The clutter return is then 630:{\displaystyle \ V_{m}\approx {\frac {\pi }{4}}(R\theta )(R\phi )(c\tau /2)} 268: 185: 4081: 1757:
Figure 2. Illustration of high- and low-angle surface-clutter illumination
3974: 3949: 3828: in this section. Unsourced material may be challenged and removed. 229: 168:. Other causes include natural objects such as terrain features, sea, 537:{\displaystyle \ V_{m}=\pi R\tan(\theta /2)R\tan(\phi /2)(c\tau /2)} 3860: 1355: 648:
is replaced by the product of the volume backscatter coefficient,
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Problems in calculating clutter for the pulse length limited case
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A Canadian Perspective on High-Frequency Over-the-Horizon Radar
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with a resulting expression for the signal to clutter ratio of
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is the back scatter coefficient of the clutter. Converting
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interval of the radar, and it no longer provides adequate
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events. This phenomenon is especially apparent near the
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Clutter suppression using amplitude weighted waveforms
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Problems in calculating signal to volume clutter ratio
1182:{\displaystyle \ A_{r}={\frac {G\lambda ^{2}}{4\pi }}} 3687: 3474: 3343: 3320: 3202: 3055: 3033: 2923: 2860: 2791: 2669: 2469: 2355: 2346:
to degrees and putting in the numerical values gives
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intersected by the beam as illustrated in Figure 2.
1617:{\displaystyle \ G={\frac {\pi ^{2}}{\theta \phi }}} 1240:{\displaystyle \ G={\frac {\pi ^{2}}{\theta \phi }}} 1877:The area illuminated by the radar is then given by 49:. Unsourced material may be challenged and removed. 3771: 3669: 3454: 3326: 3302: 3181: 3039: 3015: 2903: 2840: 2750: 2648: 2448: 2338: 2318: 2287: 2159: 2135: 2023: 1956: 1865: 1809: 1712: 1616: 1558: 1449: 1339: 1239: 1181: 1115: 934: 908: 875: 846: 813: 660: 629: 536: 422: 394: 366: 346: 323: 292: 2904:{\displaystyle \ A\approx \pi R^{2}\theta ^{2}/4} 4030:A model for high frequency radar auroral clutter 2024:{\displaystyle \ A=R(c\tau /2)\theta \sec \psi } 212:produces convection patterns in the ionospheric 4060:"Radar Clutter | SKYbrary Aviation Safety" 3859:is a term used in describing "clutter" seen by 3785:General problems in calculating surface clutter 2841:{\displaystyle \ A=\pi R^{2}\tan ^{2}\theta /2} 272:Figure 1. Illustration of illuminated Rain Cell 3987: 3985: 4001:(Technical report). Ottawa, Ontario, Canada: 3909:Journal of Atmospheric and Oceanic Technology 3903:Golbon-Haghighi, M.H.; Zhang G. (July 2019). 8: 1967:For 'small' beamwidths this approximates to 433:The volume of the illuminated cell is thus: 256:(e.g., echoes from aircraft), clutter, and 216:. Radar clutter can degrade the ability of 1358:the return from the target itself will be 3973: 3928: 3844:Learn how and when to remove this message 3761: 3752: 3743: 3730: 3720: 3714: 3691: 3686: 3655: 3645: 3624: 3614: 3604: 3597: 3589: 3580: 3574: 3564: 3555: 3540: 3530: 3520: 3508: 3498: 3491: 3478: 3473: 3466:The target return remains unchanged thus 3446: 3436: 3424: 3418: 3402: 3392: 3380: 3370: 3360: 3353: 3342: 3319: 3294: 3284: 3271: 3261: 3251: 3239: 3229: 3219: 3212: 3201: 3173: 3163: 3151: 3139: 3123: 3113: 3092: 3082: 3072: 3065: 3054: 3032: 3007: 2991: 2981: 2960: 2950: 2940: 2933: 2922: 2893: 2887: 2877: 2859: 2851:which for small beamwidths simplifies to 2830: 2818: 2808: 2790: 2740: 2731: 2705: 2696: 2673: 2668: 2634: 2624: 2603: 2593: 2583: 2576: 2567: 2542: 2533: 2523: 2513: 2502: 2496: 2486: 2473: 2468: 2440: 2421: 2406: 2395: 2385: 2375: 2368: 2354: 2331: 2310: 2304: 2279: 2252: 2241: 2231: 2221: 2214: 2205: 2195: 2185: 2174: 2152: 2127: 2111: 2101: 2080: 2070: 2060: 2053: 2042: 1998: 1975: 1934: 1911: 1885: 1843: 1829: 1821:The length measured along the surface is 1799: 1779: 1686: 1653: 1640: 1635: 1598: 1592: 1581: 1538: 1528: 1486: 1473: 1468: 1435: 1425: 1404: 1394: 1384: 1377: 1366: 1319: 1289: 1276: 1269: 1258: 1221: 1215: 1204: 1162: 1152: 1143: 1134: 1099: 1056: 1047: 1037: 1004: 994: 984: 977: 966: 927: 900: 894: 867: 861: 838: 832: 797: 754: 745: 735: 714: 704: 694: 687: 676: 653: 616: 573: 564: 555: 523: 503: 477: 450: 441: 412: 407: 384: 379: 359: 339: 316: 285: 109:Learn how and when to remove this message 3944:Golbon-Haghighi, M.H.; Zhang G.; Li Y.; 1752: 267: 4003:Defence Research and Development Canada 3895: 942:= distance from the radar to the target 3027:Substituting for the illuminated area 2147:Substituting for the illuminated area 1866:{\displaystyle \ (c\tau /2)\sec \psi } 248:Clutter-limited or noise-limited radar 4005:. p. 38. DRDC Ottawa TM 2006-285 1196:is related to the two beamwidths by: 547:For small angles this simplifies to: 140:. Such echoes are typically returned 7: 3826:adding citations to reliable sources 47:adding citations to reliable sources 3992:Riddolls, Ryan J (December 2006). 1810:{\displaystyle \ 2R\tan \theta /2} 14: 3802: 2914:The clutter return is as before 23: 3813:needs additional citations for 950:which itself approximates to a 920:(area) of the receiving antenna 34:needs additional citations for 3642: 3632: 3571: 3549: 3433: 3411: 3160: 3145: 3110: 3100: 2978: 2968: 2621: 2611: 2098: 2088: 2006: 1989: 1942: 1922: 1919: 1902: 1851: 1834: 1671: 1659: 1525: 1515: 1504: 1492: 1422: 1412: 1312: 1300: 1107: 1090: 1087: 1078: 1075: 1066: 1034: 1024: 805: 788: 785: 776: 773: 764: 732: 722: 624: 607: 604: 595: 592: 583: 531: 514: 511: 497: 485: 471: 144:, sea, rain, animals/insects, 1: 154:radar backscatter coefficient 129:cluttering the radar display 4110:Radio frequency propagation 4040:. p. 9. RADC-TR-80-122 4038:Rome Air Development Center 3193:This can be simplified to: 2319:{\displaystyle \sigma ^{o}} 2034:The clutter return is then 887:of the transmitting antenna 854:= transmitter power (Watts) 180:, birds, turbulence in the 4126: 3865:pulse repetition frequency 311:is the speed of light and 204:, where the action of the 3930:10.1175/JTECH-D-18-0147.1 1766:Pulse length limited case 395:{\displaystyle \theta /2} 305:statistically independent 3327:{\displaystyle \theta } 2778:Beam width limited case 2339:{\displaystyle \theta } 423:{\displaystyle \phi /2} 182:atmospheric circulation 3773: 3671: 3456: 3328: 3304: 3183: 3041: 3017: 2905: 2842: 2752: 2650: 2450: 2340: 2320: 2289: 2161: 2137: 2025: 1958: 1867: 1811: 1758: 1714: 1618: 1560: 1451: 1341: 1241: 1183: 1117: 936: 910: 877: 848: 815: 662: 631: 538: 424: 396: 368: 348: 325: 294: 273: 230:ionospheric reflection 218:over-the-horizon radar 130: 3774: 3672: 3457: 3329: 3305: 3184: 3042: 3018: 2906: 2843: 2753: 2651: 2451: 2341: 2321: 2290: 2162: 2138: 2026: 1959: 1868: 1812: 1756: 1715: 1619: 1561: 1452: 1342: 1242: 1184: 1118: 937: 911: 909:{\displaystyle A_{r}} 878: 876:{\displaystyle G_{t}} 849: 847:{\displaystyle P_{t}} 816: 663: 661:{\displaystyle \eta } 632: 539: 425: 397: 369: 349: 347:{\displaystyle \tau } 326: 324:{\displaystyle \tau } 295: 276:Rain, hail, snow and 271: 238:anomalous propagation 124: 3975:10.3390/atmos7060083 3822:improve this article 3685: 3679:Which simplifies to 3472: 3341: 3318: 3200: 3053: 3031: 2921: 2858: 2789: 2667: 2467: 2353: 2330: 2303: 2173: 2151: 2041: 1974: 1884: 1828: 1778: 1634: 1580: 1467: 1365: 1257: 1203: 1133: 965: 926: 893: 860: 831: 675: 652: 554: 440: 406: 378: 358: 338: 315: 284: 58:"Clutter" radar 43:improve this article 4082:10.1049/cp:19971786 4072:V. Gregers-Hansen, 3966:2016Atmos...7...83G 3921:2019JAtOT..36.1285G 3869:clutter suppression 2660:This simplifies to 646:radar cross section 226:atmospheric ducting 3769: 3667: 3452: 3324: 3300: 3179: 3037: 3013: 2901: 2838: 2748: 2646: 2446: 2336: 2316: 2285: 2157: 2133: 2021: 1954: 1863: 1807: 1759: 1710: 1614: 1556: 1447: 1337: 1237: 1179: 1113: 932: 906: 873: 844: 811: 658: 627: 534: 420: 392: 364: 344: 321: 290: 274: 194:geomagnetic storms 131: 3854: 3853: 3846: 3767: 3750: 3699: 3690: 3662: 3595: 3547: 3486: 3477: 3409: 3346: 3278: 3205: 3130: 3058: 3040:{\displaystyle A} 2998: 2926: 2863: 2794: 2772:antenna sidelobes 2746: 2729: 2681: 2672: 2641: 2574: 2540: 2494: 2481: 2472: 2412: 2358: 2258: 2212: 2178: 2160:{\displaystyle A} 2118: 2046: 1979: 1889: 1833: 1783: 1725:pulse compression 1708: 1648: 1639: 1612: 1585: 1554: 1481: 1472: 1442: 1370: 1326: 1262: 1235: 1208: 1177: 1138: 1064: 1054: 970: 952:Gaussian function 935:{\displaystyle R} 762: 752: 680: 581: 559: 445: 367:{\displaystyle R} 293:{\displaystyle R} 222:ground reflection 202:geomagnetic poles 119: 118: 111: 93: 4117: 4084: 4070: 4064: 4063: 4056: 4050: 4049: 4047: 4045: 4035: 4021: 4015: 4014: 4012: 4010: 4000: 3989: 3980: 3979: 3977: 3941: 3935: 3934: 3932: 3915:(7): 1285–1296. 3900: 3849: 3842: 3838: 3835: 3829: 3806: 3798: 3778: 3776: 3775: 3770: 3768: 3766: 3765: 3753: 3751: 3749: 3748: 3747: 3738: 3737: 3721: 3719: 3718: 3700: 3692: 3688: 3676: 3674: 3673: 3668: 3663: 3661: 3660: 3659: 3650: 3649: 3630: 3629: 3628: 3619: 3618: 3609: 3608: 3598: 3596: 3594: 3593: 3581: 3579: 3578: 3569: 3568: 3559: 3548: 3546: 3545: 3544: 3535: 3534: 3525: 3524: 3514: 3513: 3512: 3503: 3502: 3492: 3487: 3479: 3475: 3461: 3459: 3458: 3453: 3451: 3450: 3441: 3440: 3428: 3423: 3422: 3410: 3408: 3407: 3406: 3397: 3396: 3386: 3385: 3384: 3375: 3374: 3365: 3364: 3354: 3344: 3333: 3331: 3330: 3325: 3309: 3307: 3306: 3301: 3299: 3298: 3289: 3288: 3279: 3277: 3276: 3275: 3266: 3265: 3256: 3255: 3245: 3244: 3243: 3234: 3233: 3224: 3223: 3213: 3203: 3188: 3186: 3185: 3180: 3178: 3177: 3168: 3167: 3155: 3144: 3143: 3131: 3129: 3128: 3127: 3118: 3117: 3098: 3097: 3096: 3087: 3086: 3077: 3076: 3066: 3056: 3046: 3044: 3043: 3038: 3022: 3020: 3019: 3014: 3012: 3011: 2999: 2997: 2996: 2995: 2986: 2985: 2966: 2965: 2964: 2955: 2954: 2945: 2944: 2934: 2924: 2910: 2908: 2907: 2902: 2897: 2892: 2891: 2882: 2881: 2861: 2847: 2845: 2844: 2839: 2834: 2823: 2822: 2813: 2812: 2792: 2757: 2755: 2754: 2749: 2747: 2745: 2744: 2732: 2730: 2728: 2717: 2706: 2704: 2703: 2682: 2674: 2670: 2655: 2653: 2652: 2647: 2642: 2640: 2639: 2638: 2629: 2628: 2609: 2608: 2607: 2598: 2597: 2588: 2587: 2577: 2575: 2573: 2572: 2571: 2543: 2541: 2539: 2538: 2537: 2528: 2527: 2518: 2517: 2507: 2506: 2497: 2495: 2487: 2482: 2474: 2470: 2455: 2453: 2452: 2447: 2445: 2444: 2426: 2425: 2413: 2411: 2410: 2401: 2400: 2399: 2390: 2389: 2380: 2379: 2369: 2356: 2345: 2343: 2342: 2337: 2325: 2323: 2322: 2317: 2315: 2314: 2294: 2292: 2291: 2286: 2284: 2283: 2259: 2257: 2256: 2247: 2246: 2245: 2236: 2235: 2226: 2225: 2215: 2213: 2211: 2210: 2209: 2200: 2199: 2186: 2176: 2166: 2164: 2163: 2158: 2142: 2140: 2139: 2134: 2132: 2131: 2119: 2117: 2116: 2115: 2106: 2105: 2086: 2085: 2084: 2075: 2074: 2065: 2064: 2054: 2044: 2030: 2028: 2027: 2022: 2002: 1977: 1963: 1961: 1960: 1955: 1938: 1915: 1887: 1872: 1870: 1869: 1864: 1847: 1831: 1816: 1814: 1813: 1808: 1803: 1781: 1719: 1717: 1716: 1711: 1709: 1707: 1691: 1690: 1677: 1654: 1649: 1641: 1637: 1627:it follows that 1623: 1621: 1620: 1615: 1613: 1611: 1603: 1602: 1593: 1583: 1565: 1563: 1562: 1557: 1555: 1553: 1543: 1542: 1533: 1532: 1513: 1487: 1482: 1474: 1470: 1456: 1454: 1453: 1448: 1443: 1441: 1440: 1439: 1430: 1429: 1410: 1409: 1408: 1399: 1398: 1389: 1388: 1378: 1368: 1346: 1344: 1343: 1338: 1327: 1325: 1324: 1323: 1295: 1294: 1293: 1281: 1280: 1270: 1260: 1246: 1244: 1243: 1238: 1236: 1234: 1226: 1225: 1216: 1206: 1188: 1186: 1185: 1180: 1178: 1176: 1168: 1167: 1166: 1153: 1148: 1147: 1136: 1122: 1120: 1119: 1114: 1103: 1065: 1057: 1055: 1053: 1052: 1051: 1042: 1041: 1010: 1009: 1008: 999: 998: 989: 988: 978: 968: 941: 939: 938: 933: 915: 913: 912: 907: 905: 904: 882: 880: 879: 874: 872: 871: 853: 851: 850: 845: 843: 842: 820: 818: 817: 812: 801: 763: 755: 753: 751: 750: 749: 740: 739: 720: 719: 718: 709: 708: 699: 698: 688: 678: 667: 665: 664: 659: 636: 634: 633: 628: 620: 582: 574: 569: 568: 557: 543: 541: 540: 535: 527: 507: 481: 455: 454: 443: 429: 427: 426: 421: 416: 401: 399: 398: 393: 388: 373: 371: 370: 365: 353: 351: 350: 345: 330: 328: 327: 322: 299: 297: 296: 291: 242:weather balloons 148:and atmospheric 125:Different radar 114: 107: 103: 100: 94: 92: 51: 27: 19: 4125: 4124: 4120: 4119: 4118: 4116: 4115: 4114: 4090: 4089: 4088: 4087: 4071: 4067: 4058: 4057: 4053: 4043: 4041: 4033: 4023: 4022: 4018: 4008: 4006: 3998: 3991: 3990: 3983: 3943: 3942: 3938: 3902: 3901: 3897: 3892: 3857:Clutter folding 3850: 3839: 3833: 3830: 3819: 3807: 3796: 3794:Clutter folding 3787: 3757: 3739: 3726: 3725: 3710: 3683: 3682: 3651: 3641: 3631: 3620: 3610: 3600: 3599: 3585: 3570: 3560: 3536: 3526: 3516: 3515: 3504: 3494: 3493: 3470: 3469: 3442: 3432: 3414: 3398: 3388: 3387: 3376: 3366: 3356: 3355: 3339: 3338: 3316: 3315: 3290: 3280: 3267: 3257: 3247: 3246: 3235: 3225: 3215: 3214: 3198: 3197: 3169: 3159: 3135: 3119: 3109: 3099: 3088: 3078: 3068: 3067: 3051: 3050: 3029: 3028: 3003: 2987: 2977: 2967: 2956: 2946: 2936: 2935: 2919: 2918: 2883: 2873: 2856: 2855: 2814: 2804: 2787: 2786: 2780: 2767: 2736: 2718: 2707: 2692: 2665: 2664: 2630: 2620: 2610: 2599: 2589: 2579: 2578: 2563: 2547: 2529: 2519: 2509: 2508: 2498: 2465: 2464: 2436: 2417: 2402: 2391: 2381: 2371: 2370: 2351: 2350: 2328: 2327: 2306: 2301: 2300: 2275: 2248: 2237: 2227: 2217: 2216: 2201: 2191: 2190: 2171: 2170: 2149: 2148: 2123: 2107: 2097: 2087: 2076: 2066: 2056: 2055: 2039: 2038: 1972: 1971: 1882: 1881: 1826: 1825: 1776: 1775: 1768: 1751: 1742: 1740:Surface clutter 1733: 1682: 1678: 1655: 1632: 1631: 1604: 1594: 1578: 1577: 1534: 1524: 1514: 1488: 1465: 1464: 1431: 1421: 1411: 1400: 1390: 1380: 1379: 1363: 1362: 1315: 1296: 1285: 1272: 1271: 1255: 1254: 1227: 1217: 1201: 1200: 1169: 1158: 1154: 1139: 1131: 1130: 1043: 1033: 1011: 1000: 990: 980: 979: 963: 962: 924: 923: 896: 891: 890: 863: 858: 857: 834: 829: 828: 741: 731: 721: 710: 700: 690: 689: 673: 672: 650: 649: 560: 552: 551: 446: 438: 437: 404: 403: 376: 375: 356: 355: 336: 335: 313: 312: 282: 281: 266: 250: 208:on the earth’s 162: 115: 104: 98: 95: 52: 50: 40: 28: 17: 16:Unwanted echoes 12: 11: 5: 4123: 4121: 4113: 4112: 4107: 4102: 4092: 4091: 4086: 4085: 4065: 4051: 4027:(March 1980). 4016: 3981: 3936: 3894: 3893: 3891: 3888: 3877:coherent dwell 3852: 3851: 3810: 3808: 3801: 3795: 3792: 3786: 3783: 3764: 3760: 3756: 3746: 3742: 3736: 3733: 3729: 3724: 3717: 3713: 3709: 3706: 3703: 3698: 3695: 3666: 3658: 3654: 3648: 3644: 3640: 3637: 3634: 3627: 3623: 3617: 3613: 3607: 3603: 3592: 3588: 3584: 3577: 3573: 3567: 3563: 3558: 3554: 3551: 3543: 3539: 3533: 3529: 3523: 3519: 3511: 3507: 3501: 3497: 3490: 3485: 3482: 3464: 3463: 3449: 3445: 3439: 3435: 3431: 3427: 3421: 3417: 3413: 3405: 3401: 3395: 3391: 3383: 3379: 3373: 3369: 3363: 3359: 3352: 3349: 3323: 3312: 3311: 3297: 3293: 3287: 3283: 3274: 3270: 3264: 3260: 3254: 3250: 3242: 3238: 3232: 3228: 3222: 3218: 3211: 3208: 3191: 3190: 3176: 3172: 3166: 3162: 3158: 3154: 3150: 3147: 3142: 3138: 3134: 3126: 3122: 3116: 3112: 3108: 3105: 3102: 3095: 3091: 3085: 3081: 3075: 3071: 3064: 3061: 3036: 3025: 3024: 3010: 3006: 3002: 2994: 2990: 2984: 2980: 2976: 2973: 2970: 2963: 2959: 2953: 2949: 2943: 2939: 2932: 2929: 2912: 2911: 2900: 2896: 2890: 2886: 2880: 2876: 2872: 2869: 2866: 2849: 2848: 2837: 2833: 2829: 2826: 2821: 2817: 2811: 2807: 2803: 2800: 2797: 2779: 2776: 2766: 2763: 2759: 2758: 2743: 2739: 2735: 2727: 2724: 2721: 2716: 2713: 2710: 2702: 2699: 2695: 2691: 2688: 2685: 2680: 2677: 2658: 2657: 2645: 2637: 2633: 2627: 2623: 2619: 2616: 2613: 2606: 2602: 2596: 2592: 2586: 2582: 2570: 2566: 2562: 2559: 2556: 2553: 2550: 2546: 2536: 2532: 2526: 2522: 2516: 2512: 2505: 2501: 2493: 2490: 2485: 2480: 2477: 2458: 2457: 2443: 2439: 2435: 2432: 2429: 2424: 2420: 2416: 2409: 2405: 2398: 2394: 2388: 2384: 2378: 2374: 2367: 2364: 2361: 2335: 2313: 2309: 2297: 2296: 2282: 2278: 2274: 2271: 2268: 2265: 2262: 2255: 2251: 2244: 2240: 2234: 2230: 2224: 2220: 2208: 2204: 2198: 2194: 2189: 2184: 2181: 2156: 2145: 2144: 2130: 2126: 2122: 2114: 2110: 2104: 2100: 2096: 2093: 2090: 2083: 2079: 2073: 2069: 2063: 2059: 2052: 2049: 2032: 2031: 2020: 2017: 2014: 2011: 2008: 2005: 2001: 1997: 1994: 1991: 1988: 1985: 1982: 1965: 1964: 1953: 1950: 1947: 1944: 1941: 1937: 1933: 1930: 1927: 1924: 1921: 1918: 1914: 1910: 1907: 1904: 1901: 1898: 1895: 1892: 1875: 1874: 1862: 1859: 1856: 1853: 1850: 1846: 1842: 1839: 1836: 1819: 1818: 1806: 1802: 1798: 1795: 1792: 1789: 1786: 1767: 1764: 1750: 1747: 1741: 1738: 1732: 1729: 1721: 1720: 1706: 1703: 1700: 1697: 1694: 1689: 1685: 1681: 1676: 1673: 1670: 1667: 1664: 1661: 1658: 1652: 1647: 1644: 1625: 1624: 1610: 1607: 1601: 1597: 1591: 1588: 1567: 1566: 1552: 1549: 1546: 1541: 1537: 1531: 1527: 1523: 1520: 1517: 1512: 1509: 1506: 1503: 1500: 1497: 1494: 1491: 1485: 1480: 1477: 1458: 1457: 1446: 1438: 1434: 1428: 1424: 1420: 1417: 1414: 1407: 1403: 1397: 1393: 1387: 1383: 1376: 1373: 1356:radar equation 1348: 1347: 1336: 1333: 1330: 1322: 1318: 1314: 1311: 1308: 1305: 1302: 1299: 1292: 1288: 1284: 1279: 1275: 1268: 1265: 1248: 1247: 1233: 1230: 1224: 1220: 1214: 1211: 1190: 1189: 1175: 1172: 1165: 1161: 1157: 1151: 1146: 1142: 1124: 1123: 1112: 1109: 1106: 1102: 1098: 1095: 1092: 1089: 1086: 1083: 1080: 1077: 1074: 1071: 1068: 1063: 1060: 1050: 1046: 1040: 1036: 1032: 1029: 1026: 1023: 1020: 1017: 1014: 1007: 1003: 997: 993: 987: 983: 976: 973: 944: 943: 931: 921: 903: 899: 888: 870: 866: 855: 841: 837: 822: 821: 810: 807: 804: 800: 796: 793: 790: 787: 784: 781: 778: 775: 772: 769: 766: 761: 758: 748: 744: 738: 734: 730: 727: 724: 717: 713: 707: 703: 697: 693: 686: 683: 657: 642:radar equation 638: 637: 626: 623: 619: 615: 612: 609: 606: 603: 600: 597: 594: 591: 588: 585: 580: 577: 572: 567: 563: 545: 544: 533: 530: 526: 522: 519: 516: 513: 510: 506: 502: 499: 496: 493: 490: 487: 484: 480: 476: 473: 470: 467: 464: 461: 458: 453: 449: 419: 415: 411: 391: 387: 383: 363: 343: 320: 289: 265: 264:Volume clutter 262: 249: 246: 161: 158: 117: 116: 31: 29: 22: 15: 13: 10: 9: 6: 4: 3: 2: 4122: 4111: 4108: 4106: 4103: 4101: 4098: 4097: 4095: 4083: 4079: 4075: 4069: 4066: 4061: 4055: 4052: 4039: 4032: 4031: 4026: 4020: 4017: 4004: 3997: 3996: 3988: 3986: 3982: 3976: 3971: 3967: 3963: 3959: 3955: 3951: 3948:(June 2016). 3947: 3940: 3937: 3931: 3926: 3922: 3918: 3914: 3910: 3906: 3899: 3896: 3889: 3887: 3885: 3880: 3878: 3874: 3870: 3866: 3862: 3858: 3848: 3845: 3837: 3827: 3823: 3817: 3816: 3811:This section 3809: 3805: 3800: 3799: 3793: 3791: 3784: 3782: 3779: 3762: 3758: 3754: 3744: 3740: 3734: 3731: 3727: 3722: 3715: 3711: 3707: 3704: 3701: 3696: 3693: 3680: 3677: 3664: 3656: 3652: 3646: 3638: 3635: 3625: 3621: 3615: 3611: 3605: 3601: 3590: 3586: 3582: 3575: 3565: 3561: 3556: 3552: 3541: 3537: 3531: 3527: 3521: 3517: 3509: 3505: 3499: 3495: 3488: 3483: 3480: 3467: 3447: 3443: 3437: 3429: 3425: 3419: 3415: 3403: 3399: 3393: 3389: 3381: 3377: 3371: 3367: 3361: 3357: 3350: 3347: 3337: 3336: 3335: 3321: 3295: 3291: 3285: 3281: 3272: 3268: 3262: 3258: 3252: 3248: 3240: 3236: 3230: 3226: 3220: 3216: 3209: 3206: 3196: 3195: 3194: 3174: 3170: 3164: 3156: 3152: 3148: 3140: 3136: 3132: 3124: 3120: 3114: 3106: 3103: 3093: 3089: 3083: 3079: 3073: 3069: 3062: 3059: 3049: 3048: 3047: 3034: 3008: 3004: 3000: 2992: 2988: 2982: 2974: 2971: 2961: 2957: 2951: 2947: 2941: 2937: 2930: 2927: 2917: 2916: 2915: 2898: 2894: 2888: 2884: 2878: 2874: 2870: 2867: 2864: 2854: 2853: 2852: 2835: 2831: 2827: 2824: 2819: 2815: 2809: 2805: 2801: 2798: 2795: 2785: 2784: 2783: 2777: 2775: 2773: 2764: 2762: 2741: 2737: 2733: 2725: 2722: 2719: 2714: 2711: 2708: 2700: 2697: 2693: 2689: 2686: 2683: 2678: 2675: 2663: 2662: 2661: 2643: 2635: 2631: 2625: 2617: 2614: 2604: 2600: 2594: 2590: 2584: 2580: 2568: 2564: 2560: 2557: 2554: 2551: 2548: 2544: 2534: 2530: 2524: 2520: 2514: 2510: 2503: 2499: 2491: 2488: 2483: 2478: 2475: 2463: 2462: 2461: 2441: 2437: 2433: 2430: 2427: 2422: 2418: 2414: 2407: 2403: 2396: 2392: 2386: 2382: 2376: 2372: 2365: 2362: 2359: 2349: 2348: 2347: 2333: 2311: 2307: 2280: 2276: 2272: 2269: 2266: 2263: 2260: 2253: 2249: 2242: 2238: 2232: 2228: 2222: 2218: 2206: 2202: 2196: 2192: 2187: 2182: 2179: 2169: 2168: 2167: 2154: 2128: 2124: 2120: 2112: 2108: 2102: 2094: 2091: 2081: 2077: 2071: 2067: 2061: 2057: 2050: 2047: 2037: 2036: 2035: 2018: 2015: 2012: 2009: 2003: 1999: 1995: 1992: 1986: 1983: 1980: 1970: 1969: 1968: 1951: 1948: 1945: 1939: 1935: 1931: 1928: 1925: 1916: 1912: 1908: 1905: 1899: 1896: 1893: 1890: 1880: 1879: 1878: 1860: 1857: 1854: 1848: 1844: 1840: 1837: 1824: 1823: 1822: 1804: 1800: 1796: 1793: 1790: 1787: 1784: 1774: 1773: 1772: 1765: 1763: 1755: 1748: 1746: 1739: 1737: 1730: 1728: 1726: 1704: 1701: 1698: 1695: 1692: 1687: 1683: 1679: 1674: 1668: 1665: 1662: 1656: 1650: 1645: 1642: 1630: 1629: 1628: 1608: 1605: 1599: 1595: 1589: 1586: 1576: 1575: 1574: 1571: 1550: 1547: 1544: 1539: 1535: 1529: 1521: 1518: 1510: 1507: 1501: 1498: 1495: 1489: 1483: 1478: 1475: 1463: 1462: 1461: 1444: 1436: 1432: 1426: 1418: 1415: 1405: 1401: 1395: 1391: 1385: 1381: 1374: 1371: 1361: 1360: 1359: 1357: 1352: 1334: 1331: 1328: 1320: 1316: 1309: 1306: 1303: 1297: 1290: 1286: 1282: 1277: 1273: 1266: 1263: 1253: 1252: 1251: 1231: 1228: 1222: 1218: 1212: 1209: 1199: 1198: 1197: 1195: 1173: 1170: 1163: 1159: 1155: 1149: 1144: 1140: 1129: 1128: 1127: 1110: 1104: 1100: 1096: 1093: 1084: 1081: 1072: 1069: 1061: 1058: 1048: 1044: 1038: 1030: 1027: 1021: 1018: 1015: 1012: 1005: 1001: 995: 991: 985: 981: 974: 971: 961: 960: 959: 957: 953: 949: 948:sinc function 929: 922: 919: 901: 897: 889: 886: 868: 864: 856: 839: 835: 827: 826: 825: 808: 802: 798: 794: 791: 782: 779: 770: 767: 759: 756: 746: 742: 736: 728: 725: 715: 711: 705: 701: 695: 691: 684: 681: 671: 670: 669: 655: 647: 643: 621: 617: 613: 610: 601: 598: 589: 586: 578: 575: 570: 565: 561: 550: 549: 548: 528: 524: 520: 517: 508: 504: 500: 494: 491: 488: 482: 478: 474: 468: 465: 462: 459: 456: 451: 447: 436: 435: 434: 431: 417: 413: 409: 389: 385: 381: 361: 341: 334: 318: 310: 306: 301: 287: 279: 270: 263: 261: 259: 255: 247: 245: 243: 239: 235: 231: 227: 223: 219: 215: 211: 210:magnetosphere 207: 203: 199: 198:space weather 195: 191: 187: 183: 179: 175: 171: 170:precipitation 167: 159: 157: 155: 151: 147: 143: 139: 135: 128: 123: 113: 110: 102: 99:December 2016 91: 88: 84: 81: 77: 74: 70: 67: 63: 60: –  59: 55: 54:Find sources: 48: 44: 38: 37: 32:This article 30: 26: 21: 20: 4105:Radar theory 4068: 4054: 4042:. Retrieved 4029: 4019: 4007:. Retrieved 3994: 3957: 3953: 3946:Doviak R. J. 3939: 3912: 3908: 3898: 3881: 3856: 3855: 3840: 3834:January 2024 3831: 3820:Please help 3815:verification 3812: 3788: 3780: 3681: 3678: 3468: 3465: 3313: 3192: 3026: 2913: 2850: 2781: 2768: 2760: 2659: 2459: 2298: 2146: 2033: 1966: 1876: 1820: 1769: 1760: 1749:Beam filling 1743: 1734: 1722: 1626: 1572: 1568: 1459: 1353: 1349: 1249: 1194:antenna gain 1191: 1125: 945: 916:= effective 823: 639: 546: 432: 332: 308: 302: 275: 251: 163: 133: 132: 105: 96: 86: 79: 72: 65: 53: 41:Please help 36:verification 33: 3873:fill pulses 3334:to degrees 3314:Converting 178:dust storms 150:turbulences 142:from ground 4100:Atmosphere 4094:Categories 4044:2 December 4025:Elkins, TJ 4009:2 December 3954:Atmosphere 3890:References 3884:dwell time 956:beam width 234:refraction 206:solar wind 192:caused by 190:ionosphere 174:hail spike 69:newspapers 3960:(6): 83. 3759:σ 3755:σ 3728:θ 3708:× 3665:σ 3639:π 3622:λ 3587:σ 3562:θ 3538:λ 3444:σ 3416:θ 3378:λ 3322:θ 3292:σ 3282:θ 3259:π 3237:λ 3171:σ 3149:θ 3133:π 3107:π 3090:λ 3005:σ 2975:π 2958:λ 2885:θ 2871:π 2868:≈ 2828:θ 2825:⁡ 2802:π 2738:σ 2734:σ 2726:θ 2723:τ 2715:ψ 2712:⁡ 2698:− 2690:× 2644:σ 2618:π 2601:λ 2565:σ 2561:ψ 2558:⁡ 2552:θ 2549:τ 2531:λ 2438:σ 2434:ψ 2431:⁡ 2419:θ 2415:τ 2393:λ 2334:θ 2308:σ 2277:σ 2273:ψ 2270:⁡ 2264:θ 2261:τ 2239:λ 2203:π 2125:σ 2095:π 2078:λ 2019:ψ 2016:⁡ 2010:θ 1996:τ 1952:ψ 1949:⁡ 1932:θ 1929:⁡ 1909:τ 1861:ψ 1858:⁡ 1841:τ 1797:θ 1794:⁡ 1705:η 1702:τ 1696:ϕ 1693:θ 1680:π 1675:σ 1666:⁡ 1609:ϕ 1606:θ 1596:π 1551:η 1548:τ 1522:π 1511:σ 1499:⁡ 1445:σ 1419:π 1402:λ 1354:From the 1335:η 1332:τ 1307:⁡ 1287:λ 1232:ϕ 1229:θ 1219:π 1174:π 1160:λ 1111:η 1097:τ 1085:ϕ 1073:θ 1059:π 1031:π 1019:⁡ 809:η 795:τ 783:ϕ 771:θ 757:π 729:π 656:η 614:τ 602:ϕ 590:θ 576:π 571:≈ 521:τ 501:ϕ 495:⁡ 475:θ 469:⁡ 460:π 410:ϕ 382:θ 342:τ 319:τ 196:or other 127:artifacts 3875:to each 1192:and the 918:aperture 644:but the 3962:Bibcode 3917:Bibcode 236:(e.g., 134:Clutter 83:scholar 4076:1997, 3689:  3476:  3345:  3204:  3057:  2925:  2862:  2793:  2671:  2471:  2357:  2299:where 2177:  2045:  1978:  1888:  1832:  1782:  1638:  1584:  1573:Since 1471:  1369:  1261:  1207:  1137:  969:  824:where 679:  558:  444:  374:, are 254:signal 214:plasma 186:meteor 184:, and 160:Causes 138:radars 85:  78:  71:  64:  56:  4034:(PDF) 3999:(PDF) 3861:radar 3462:Watts 3310:Watts 3189:Watts 3023:Watts 2656:Watts 2456:Watts 2295:Watts 2143:Watts 278:chaff 258:noise 166:chaff 146:chaff 90:JSTOR 76:books 4046:2023 4011:2023 3705:5.25 2492:1300 2366:1300 1490:1024 1298:1024 885:gain 402:and 62:news 4078:doi 3970:doi 3925:doi 3824:by 3553:180 3430:180 2816:tan 2709:cos 2555:sec 2428:sec 2267:sec 2013:sec 1946:sec 1926:tan 1855:sec 1791:tan 1663:log 1496:log 1304:log 1016:log 492:tan 466:tan 228:or 156:). 45:by 4096:: 3984:^ 3968:. 3956:. 3952:. 3923:. 3913:36 3911:. 3907:. 3886:. 3712:10 2694:10 1657:16 883:= 244:. 224:, 176:, 172:, 4080:: 4062:. 4048:. 4013:. 3978:. 3972:: 3964:: 3958:7 3933:. 3927:: 3919:: 3847:) 3841:( 3836:) 3832:( 3818:. 3763:o 3745:2 3741:R 3735:2 3732:o 3723:1 3716:4 3702:= 3697:C 3694:S 3657:4 3653:R 3647:3 3643:) 3636:4 3633:( 3626:2 3616:2 3612:G 3606:t 3602:P 3591:o 3583:1 3576:2 3572:) 3566:o 3557:/ 3550:( 3542:2 3532:2 3528:G 3522:t 3518:P 3510:2 3506:R 3500:4 3496:4 3489:= 3484:C 3481:S 3448:o 3438:2 3434:) 3426:/ 3420:o 3412:( 3404:2 3400:R 3394:4 3390:4 3382:2 3372:2 3368:G 3362:t 3358:P 3351:= 3348:C 3296:o 3286:2 3273:2 3269:R 3263:2 3253:4 3249:4 3241:2 3231:2 3227:G 3221:t 3217:P 3210:= 3207:C 3175:o 3165:2 3161:) 3157:2 3153:/ 3146:( 3141:2 3137:R 3125:4 3121:R 3115:3 3111:) 3104:4 3101:( 3094:2 3084:2 3080:G 3074:t 3070:P 3063:= 3060:C 3035:A 3009:o 3001:A 2993:4 2989:R 2983:3 2979:) 2972:4 2969:( 2962:2 2952:2 2948:G 2942:t 2938:P 2931:= 2928:C 2899:4 2895:/ 2889:2 2879:2 2875:R 2865:A 2836:2 2832:/ 2820:2 2810:2 2806:R 2799:= 2796:A 2742:o 2720:R 2701:7 2687:4 2684:= 2679:C 2676:S 2636:4 2632:R 2626:3 2622:) 2615:4 2612:( 2605:2 2595:2 2591:G 2585:t 2581:P 2569:o 2545:1 2535:2 2525:2 2521:G 2515:t 2511:P 2504:3 2500:R 2489:1 2484:= 2479:C 2476:S 2442:o 2423:o 2408:3 2404:R 2397:2 2387:2 2383:G 2377:t 2373:P 2363:= 2360:C 2312:o 2281:o 2254:3 2250:R 2243:2 2233:2 2229:G 2223:t 2219:P 2207:3 2197:7 2193:2 2188:c 2183:= 2180:C 2155:A 2129:o 2121:A 2113:4 2109:R 2103:3 2099:) 2092:4 2089:( 2082:2 2072:2 2068:G 2062:t 2058:P 2051:= 2048:C 2007:) 2004:2 2000:/ 1993:c 1990:( 1987:R 1984:= 1981:A 1943:) 1940:2 1936:/ 1923:( 1920:) 1917:2 1913:/ 1906:c 1903:( 1900:R 1897:2 1894:= 1891:A 1873:. 1852:) 1849:2 1845:/ 1838:c 1835:( 1817:. 1805:2 1801:/ 1788:R 1785:2 1699:c 1688:2 1684:R 1672:) 1669:2 1660:( 1651:= 1646:C 1643:S 1600:2 1590:= 1587:G 1545:c 1540:2 1536:R 1530:3 1526:) 1519:4 1516:( 1508:G 1505:) 1502:2 1493:( 1484:= 1479:C 1476:S 1437:4 1433:R 1427:3 1423:) 1416:4 1413:( 1406:2 1396:2 1392:G 1386:t 1382:P 1375:= 1372:S 1329:c 1321:2 1317:R 1313:) 1310:2 1301:( 1291:2 1283:G 1278:t 1274:P 1267:= 1264:C 1223:2 1213:= 1210:G 1171:4 1164:2 1156:G 1150:= 1145:r 1141:A 1108:) 1105:2 1101:/ 1094:c 1091:( 1088:) 1082:R 1079:( 1076:) 1070:R 1067:( 1062:4 1049:4 1045:R 1039:2 1035:) 1028:4 1025:( 1022:2 1013:2 1006:r 1002:A 996:t 992:G 986:t 982:P 975:= 972:C 930:R 902:r 898:A 869:t 865:G 840:t 836:P 806:) 803:2 799:/ 792:c 789:( 786:) 780:R 777:( 774:) 768:R 765:( 760:4 747:4 743:R 737:2 733:) 726:4 723:( 716:r 712:A 706:t 702:G 696:t 692:P 685:= 682:C 625:) 622:2 618:/ 611:c 608:( 605:) 599:R 596:( 593:) 587:R 584:( 579:4 566:m 562:V 532:) 529:2 525:/ 518:c 515:( 512:) 509:2 505:/ 498:( 489:R 486:) 483:2 479:/ 472:( 463:R 457:= 452:m 448:V 418:2 414:/ 390:2 386:/ 362:R 333:c 309:c 288:R 232:/ 112:) 106:( 101:) 97:( 87:· 80:· 73:· 66:· 39:.

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artifacts
radars
from ground
chaff
turbulences
radar backscatter coefficient
chaff
precipitation
hail spike
dust storms
atmospheric circulation
meteor
ionosphere
geomagnetic storms
space weather
geomagnetic poles
solar wind
magnetosphere

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