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VHF-RADAR OBSERVATIONS OF TEMPERATURE SHEETS INTHE STRATOSPHERIC-TROPOSPHERIC REGION1. Introduction:Siddarth Shankar Das 1 , K. Kishore Kumar 1 , A. R. Jain 1 ,D. Narayana Rao 1 , A.K.Ghosh 1 , K. Nakamura 21 National MST Radar Facility, P.B.123, Tirupati-517502. India.2 Nagoya University, Nagoya-464-8601, Japan.E-mail : dassiddhu@rediffmail.comIn past two decades VHF radar observations have contributed much in understandingthe various small-scale atmospheric processes. However, knowledge of the VHF radarbackscattering plays a vital role in understanding and interpreting these observed atmosphericphenomena. In this regard, several experiments were carried out across the globe tounderstand the VHF radar backscattering mechanisms. Many of these experiments havereported the multiple layered structures at and around the tropopause regions, especially inthe lower stratosphere [e.g. Jaya Rao et al., 1994, Jain et al., 1994 and 2001]. It is now wellestablished that these layered structures are due to the presence of strong negative andpositive temperature gradients [e.g. Dalaudier et al., 1994, Luce et al., 2001], commonlyknown as ‘temperature sheets’. VHF radar observations of these temperature sheets in thelower stratosphere are extensively reported by several researchers [Dalaudier et al., 1994],[Luce et al., 2001, Jayarao, et al., 1994]. Though, earlier studies have suggested fewcausative mechanisms for the formation of temperature sheets, they are restricted by means ofuncertainty in their proposed mechanism and also due to limited radar resolutions (interms ofspatial and temporal). The suggested mechanisms include Kelvin-Helmholtz Instability,(KHI) [Muschinski and Wode, 1998], viscous or thermal conductive waves [Hockings et al.1991] and gravity waves [Luce et al., 2001]. It has been further showed that the propagationand dissipation of gravity waves, which in turn affected by the KHI [Frittis and Rastogi,1985], is responsible for the observed temperature sheets in the lower stratosphere.In the present study, simultaneous VHF radar located at Gadanki (13.47 o N, 79.18 o E,a tropical site, India) and balloon measurements have been employed to divulge theoccurrence of temperature sheets. An attempt has also been made to understand the causativemechanism for the presence of multiple layers structure in terms of gravity waves.2. Results and Discussions:The results from concurrent VHF Radar observations at Gadanki and GPS sondemeasurements at Tirupati (nearby the radar site) during September 2000 are presented here.GPS sondes provides high-resolutions measurements of temperature, pressure, humidity,wind speed and direction. A temperature profile obtained from GPS sonde, on September 4,2000, is shown in figure 1(a). This figure displays clearly the existence of inversion layers, bystrong positive and negative temperature gradients in the stratospheric-tropospheric heightregions. The recorded radar observations interms of range-time signal to noise ratio (SNR)section is shown in figure 1(b). This figure reveals the existence of multiple layeredstructures in the lower stratosphere and upper troposphere height regions. It further illustratesthat the high intensity in SNR is due to the prevailing temperature gradient at the same heightregion (refer figure 1(a)). Radar measurements at vertical and off-vertical directions providethe measure of aspect sensitivity of the backscatters. The difference in SNR profiles ofvertical and off-vertical directions, which gives the first order aspect sensitivity70
measurements, is shown in figure 1(c). From this figure high aspect sensitivity can be noticedaround the temperature sheets, which in turn confirms the layered structure of thebackscatters.In order to know the vertical wave length of temperature and SNR perturbations,wave analysis have been carried out and is shown in figure 2. As there was no continuousradar observations, the wave anlysis is done in height domain only to find out the verticalwavelenth of the observed perturbations. Both SNR and temperature show a peak inamplitude at the vertical wavelength of 1.6 km. This suggests that the modulation oftemperature is due to the propagation of atmospheric waves, which in turn reflects in theSNR observations. As mentioned earlier,due to the lack of continuous observations (bothtemperature and radar intensity), wave periodicities are not estimated.Realizing the importance of these studies a comprehensive campaign is carried out tofurther understand the existence of temperature sheets. During this campaign, we found asimilar kind of structure as discussed above on September 25, 2002. On this day, continuousradar observations were taken for a period of 12 hours with time and height resolutions of7min and 150 m respectively. The radar observations are also supported by the simultaneousGPS measurements at the radar site. Figure 3(a) shows the height profile of temperature,which is revealing the prominent temperature structures in the lower stratosphere.September 4, 2000SNR (dB)(a) (b) (c)Figure 1. (a) Height profile of temperature derived from GPS-Sonde measurements, (b)Height-Time-SNR section obtained from Gadanki VHF radar and (c) height profile of SNRdifference between vertical and off-vertical (10°) beam directions on September 4, 2000.September 4, 2000Figure 2. Vertical wave number spectra of temperature and SNR obtained on September 42000 (arrow indicates the dominant wave number)71
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MST10Tenth InternationalWORKSHOPOn
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MST 10 Group PictureMay 15 th , 200
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TENTH INTERNATIONAL WORKSHOP ON TEC
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Table of ContentsPREFACE ..........
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I.2.18 FURTHER OBSERVATIONS OF PMSE
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I.3.27 NEW MST RADAR METHODS FOR ME
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I.4.19 STUDY OF A MESOSCALE LAND-TO
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I.5.502 AN ATTEMPT TO CALIBRATE THE
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PrefaceMST10The Tenth International
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and the local organizing committee,
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The operational aspects and recent
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To improve the understanding of dyn
Page 25 and 26: Improving MST radar resolution by u
Page 27 and 28: latitudes, arguing that the former
Page 29 and 30: Report on Session I.3 “Winds, Wav
Page 31 and 32: Turbulence.The session then moved i
Page 33 and 34: Report on Session I.4 “Meteorolog
Page 35 and 36: Multiple Antenna Profiling Radar (M
Page 37 and 38: Report on Session II “Novel Persp
Page 39 and 40: synchronized by GPS and connected v
Page 41 and 42: The highly positive response of the
Page 43 and 44: 10th International Workshop on Tech
Page 45 and 46: 10th International Workshop on Tech
Page 47 and 48: Session I.1: Radar scattering proce
Page 49 and 50: ⎡7800 ∂q⎤(3)⎢ 15500q⎥M =
Page 51 and 52: Figure 2 compares profiles of ω B
Page 53 and 54: Figure 1: Data from the MST radar a
Page 55 and 56: Ri =shear2ωB22⎛ ∂u⎞ ⎛ ∂v
Page 57 and 58: Meridional (deg)1050−5−10Echo P
Page 59 and 60: Subarray Configuration, Capon Metho
Page 61 and 62: Fig. 2 PMSE plot (SOUSY Svalbard Ra
Page 63 and 64: VHF radar interferometry had shown
Page 65 and 66: turbulence. From Figures 1 and 2, i
Page 67 and 68: SummaryFrom the aspect sensitivity
Page 69 and 70: a specific range. In this work, syn
Page 71 and 72: P C(dB)(a) Echo Power60504030200.70
Page 73 and 74: most occidental area of South Ameri
Page 75: Quegan, 1992). It should be useful
Page 79: The present observations thus empha
Page 82 and 83: RECENT OBSERVATIONS OF E REGION FIE
Page 84 and 85: measured spectra in order to separa
Page 86 and 87: drifts at E and F regions heights b
Page 88 and 89: • Are characterized by type II ec
Page 90 and 91: The main parameters that could be o
Page 92 and 93: THE ROLE OF UNSTABLE SPORADIC-E LAY
Page 94 and 95: (σ H / σ P )E y (where σ H and
Page 96: STUDY OF A LOW E-REGION QUASI-PERIO
Page 99 and 100: 100 m/syrFigure 4: Geometry of the
Page 101 and 102: Where the notations carry same mean
Page 103 and 104: Where dx/dt and dy/dt are the veloc
Page 105 and 106: non-negativity of the image is prio
Page 107 and 108: spectrum corresponding to the backs
Page 109 and 110: The Artigas and Machu-Picchu Statio
Page 111 and 112: Arguments against the second altern
Page 113 and 114: Extension of the Kolmogorov spectru
Page 115 and 116: volumeESRvolumeSSRSSR SSRESR ESRSSR
Page 117 and 118: individual particles in a statistic
Page 119 and 120: Anomalous spectraTalkner [4] studie
Page 121 and 122: To observe the E region FAI echoes,
Page 123 and 124: matter daytime or nighttime and are
Page 125 and 126: two sub-arrays, each sub-array made
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4. SummaryHere we describe a radio
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Figure 1. E-region DPS4 spectra, ri
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effects. It is therefore plausible
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1996 and high in 2002). The electri
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electric fields map along the geoma
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SNR condition is always difficult a
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Figure-4 Power spectrum plots of a
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As we show below, Jicamarca offers
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particularly during daytime counter
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where ˆδ nm = (δ l − δ m )
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PMSE is more easily interpreted as
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ResultsTemperature climatology• s
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Simultaneous PMSE and NLC observati
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ResultsSeasonal variationMSE are no
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Figure 2: MSE parameters as functio
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Session I.3: Winds, waves and turbu
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poor. It was shown that poor perfor
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The use of diffraction pattern simi
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F 13 (ξ x ′) = (1 − cos 2ψ N)
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Figure 3: (a) Baseline length depen
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3. ResultsFigure 1 shows the amplit
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variability.Figure 4 shows the aver
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Figure 1. Period-time amplitude wav
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the 12-h and 24-h periodicities in
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winds and variances at altitudes 70
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similar correlation with larger mag
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of the refraction index are not equ
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Fig. 8. Zonal wind (top) and temper
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STUDIES ON ATMOSPHERIC GRAVITY WAVE
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1100-1200 hours. From this plot 6.3
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STUDIES ON WINDS AND MOMENTUM FLUXE
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3.4 Monthly variation of momentum f
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DEEP PENETRATIVE CONVECTION AND GEN
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ly changes direction with time with
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189
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191
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193
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These two last relations are the on
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3.2.1 From v ′2 to ɛ kThe questi
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5.2 Frequency distributionsSeveral
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ReferencesAlisse J.-R. and C. Sidi.
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Röttger J. and C.H. Liu. Partial r
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Specular reflection is negligible f
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−0.5C n2 Distribution (PROUST & S
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the beamwidth, α is the zenith ang
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this latitude in late April). Surfa
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Fig. 1. Median (upper) winds and (l
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Fig.1. Lines of constant radial vel
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which have not yet been considered
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is calculated from the radiosonde t
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Figure 3: Time-altitude cross-secti
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Absorption of cosmic noise is cause
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Incoherent scatter spectracompared
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variations of spectral widths, refr
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Figure 1. Diurnal variation of Turb
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further experimental test of the ST
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waves can be observed more clearly
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winter and a minimum in summer near
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The main recently assumed mechanism
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Figure 2. Statistics of numbers of
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LIDAR OBSERVATIONS OF MIDDLE ATMOSP
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latitudinal dependence of the seaso
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APPLICATION OF THE DUAL-BEAMWIDTH M
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Figure 2: Mean zonal and meridional
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JLKLLK/ILIL6II/G/II/G/LEODFLK/LO/DD
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The monthly diurnal mean of horizon
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Session I.4: Meteorological Phenome
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Integration of the VHF wind profile
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Figure 1 : Map of the Lago Maggiore
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precipitating clouds, the cyclonic
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Eyewall(a)(b)(c)(d)Fig. 3: Radius-h
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as low as 0.55. The Piura 50-MHz ra
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place features in the profile with
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• Period 1 (June 1-10): SCCs exis
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Sumatera occurs by stratiform cloud
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very interesting to note the double
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20(a) Convective Region(b) Transiti
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Typhoon LekimaFig. 2 Typhoon Lekima
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Fig. 5 Passage of typhoon Hayan on
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the 50 cm 2 sensor head, enabling t
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22 June 2000 23:22:23 - 23:24:20 at
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the time-height section of a convec
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Thurai, M., T.Iguchi,T. Kozu, J.D.E
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There are two main mechanisms which
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Horel, J.D. and Cornejo-Garrido, A.
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estimating two independent and redu
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RASS THETA (K) RASS v-component (m/
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Surface winds usually range from 10
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weak (maximum of 5 m s -1 ) and the
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The vertical component from the VTB
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Figure 8 shows the profile of virtu
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2 3D ( , ) ( ) ( ) ˆ ( ) ˆp∆ xm
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presented in Praskovsky et al. (200
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In Fig. 2 a sketch of a mountain le
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In Fig. 8 the lamina is aligned on
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Figure 1: composite day (13 days) o
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virtual sensible heat fluxes ( Wm-2
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3. Characteristics of precipitation
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Fig. 3: Horizontal distribution of
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3. Results and discussionUHF profil
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Figure 4. Monthly variation of slop
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system with two receiving antennae,
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cycle of precipitation. Figure 3(a)
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Histogram of Zonal Velocityh=5.13 K
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5. Summary of results and concludin
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the two nearby major cities, Chenna
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Boundary layer height, km32.521.5(a
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Figure 1:Data from the MST radar at
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spectral processing. In this partic
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3. Results and discussionIn the pre
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4. SummaryAn attempt has been made
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The purpose of this study is to exa
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Figure1. Three-day average of momen
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3. The improved method to estimate
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But in case of period until 1800 UT
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Session I.5: Operational Aspects an
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The profilers of WINDAS weredesigne
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NOAA, 1994 : Wind profiler assessme
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FIRST RESULTS OF THE BOUNDARY LAYER
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Figure 3. Pulse Design Diagram to s
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MOVEABLE UHF/S-BAND PROFILER/DISDRO
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one-minute Z values determined from
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TOWARD A MULTISENSOR GROUND BASED R
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3. Cloud Evolution Case StudyOn the
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DEVELOPMENT OF A DIGITAL RECEIVER F
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Experiment 1 Experiment 2IPP 999Km
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ELECTRONIC DIGITAL BEAMFORMING IMPL
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The main element of the unit (figur
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.ON-LINE ADAPTIVE DC-GROUND-CLUTTER
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esulting in a widening of the bandw
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ON THE RADIATION EFFICIENCY OF COCO
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Table 2: Experiment #1 results, Tra
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A NEW NARROW BEAM MF RADAR AT 3 MHZ
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Off-zenith beams towards N, S, E, W
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95ALWIN VHF radar: signal powerdB80
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ANTENNA BEAM VERIFICATION USING COS
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Figure 2: A 45 MHz reference sky te
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AN ATTEMPT TO CALIBRATE THE UHF STR
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is at 4.7 km, but in the first 4-ga
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QUALITY CONTROL FOR DOPPLER WIND PR
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The resulting moments are subjected
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SOUSY RADAR AT JICAMARCA: SYSTEM DE
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NEControl andcomputer roomCompCoute
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THE EQUATORIAL ATMOSPHERE RADAR:SYS
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Table 1: Specifications of the EAR
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VHF ATMOSPHERIC AND METEOR RADAR IN
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ased upon a geotechnical engineerin
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VORTICAL MOTIONS OBSERVED WITH THE
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interpolation from the original gri
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A NEW MINIRADAR TO INVESTIGATE URBA
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e eliminated to analyze correctly t
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Session PWG 1: System Calibrations
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Session PWG 2: Data Analysis, Valid
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• the time series vectors x(k) of
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Fig. 4: reflectivity of the hydrome
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Session PWG 3: Accuracies and Requi
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Session PWG 4: International Collab
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Session II.E: NOVEL PERSPECTIVES AN
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2 Proposed AlgorithmReceived signal
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N#4E-1-16E1A1#1#2A-1-1C1#3C-1-19Fig
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of conventional DCMP, with which th
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applying the directional constraint
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while for a beam of finite width, t
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In order to make the process more q
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WHAT IS TURBULENCE SEEN BY VHF RADA
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Enhanced resolution applyingpulse s
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Beckmann, Spizichino, 1964Fig. 8 Po
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Fig. 11 Plots of temporal variation
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Fig. 14 Distributions of phase cent
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Hocking, W.K., Radar studies of sma
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THE STRUCTURE FUNCTION-BASED APPROA
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{ Ui( t), Vi( t), Wi( t)} = { Ui ,
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161). Assumption 2H: the instantane
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Only the second order SF are consid
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fluctuations umk( t ) along the bas
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VHF PARASITIC RADAR INTERFEROMETRYF
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• All the costs of transmitter pr
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Figure 2: Example of range-azimuth
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Target Altitude, km1009080706050403
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ReferencesGriffiths, H. D., A. J. G
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Participants ListAvery, James P.Uni
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Hysell, David L.EAS/Cornell Univers
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Silva, Robert R.ATRADAustraliarsilv
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AAdachi, A. .......................
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TTabary, P. .......................
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