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SPORADIC E LAYER DEPENDENCE ON PLANETARY WAVES.AN EVENT STUDY SHOWING AN INDIRECT RELATIONSHIPTROUGH MODULATED ATMOSPHERIC TIDESChristos Haldoupis 1 and Dora Pancheva 21: Physics Department, University of Crete, Iraklion, Crete, Greece2: Department of Electronic and Electrical Engineering, University of Bath, Bath, UK1. Introduction.The sporadic E layers (E s ), which are thin layers of dense plasma forming in the midlatitudeE region ionosphere, have been the subject of numerous investigations over many years (e.g.,see review by Mathews, 1998). Their formation is governed by the complexity of neutralwind dynamics in the mesosphere and lower thermosphere (MLT). In particular, the diurnaland semidiurnal tides, and the vertical wind shears carried by them, are of fundamentalimportance to E s , which sometimes are referred to as "tidal ion layers". In addition to theundisputed role of atmospheric tides, recent results suggested that planetary waves (PW) playa role on E s formation as well, a fact that went unnoticed in the long-going research ofsporadic E. The first indirect evidence for a link between E s and PW was provided by fieldalignedbackscatter observations (obtained with the MU radar in Japan and the SESCATsystem in Crete, Greece) that showed PW-period like modulations in the occurrence ofmagnetic aspect-sensitive E region radar echoes which relate with strong sporadic E layers.Here we combine and summarize the results of two recent studies on the PW - E s relationshippublished in JGR by Haldoupis and Pancheva [2002] (hereafter called Paper A), andPancheva et al. [2003] (Paper B). Paper A provided the first direct evidence in favor of aPW role on E s generation, whereas Paper B showed that planetary waves can affect E sformation indirectly through nonlinear interaction and modulation of the semidiurnal anddiurnal atmospheric tides. Both of these studies relied on a conspicuous PW event thatoccurred in August-September 1993 and detected in MLT ground radar and satellite windmeasurements (e.g., Clark et al., 2002 and references therein). This large scale atmosphericwave was a westward propagating 7-day PW of zonal number S = 1 that lasted for about 25days, seen mostly in the meridional wind with peak amplitudes in excess of 15 m/s.2. Direct Evidence for PW Modulation of Sporadic E LayersGiven the dominant 7-day PW event in August-September 1993 and the need to prove (ordisprove) the postulated PW- E s relationship, we obtained from the Colorado World DataCenter mean hourly E s critical frequency (foEs) time series for all the northern hemispheremidlatitude stations. In this respect, we found usable data from 8 stations spanning from 58 o Eto 157 o W, that is, covering about 215 o in longitude around the globe. A first look inspectionof the hourly mean foEs times series has been surprisingly reassuring, as all stations appearedto have recorded a long period modulation in foEs during the 7-day PW occurrence.164To investigate the spectral dynamics of all eight time series we applied wavelet transformtechniques. The wavelet spectrograms showed a dominant 7-day periodicity to be present,from about middle of August and well into September, in all eight ionosonde stations fromthe eastmost Ashkhabad to the westmost Maui. This is illustrated in Figure 1 which showswavelet spectrograms for all eight stations. The foEs wavelike modulation maximizeseverywhere around end of August, very much in agreement with the maximum of the 7-dayPW activity observed in the meridional component of the mesospheric neutral wind, asdiscussed by Clark et al. [2002]. We stress that this 7-day periodicity did not relate to aglobal geomagnetic activity, as confirmed from similar 3-hourly Ap wavelet analysis.
Figure 1. Period-time amplitude wavelet spectrograms for the mean hourly foEs time seriesseen simultaneously in all eight ionosonde stations. All stations see a dominant 7-daymodulation during the 2 nd half of August and into September 1993.The observation of the 7-day PW periodicity in foEs over a large latitudinal zone, suggestedan alternative way for computing PW parameters, like the zonal wavenumber and thepropagation properties of the wave. By using 3 independent methods for analysis (for detailssee Paper A) we calculated a 7-day period westward propagating S = 1 wave with a zonalphase velocity near 30 m/s which is in good agreement with the results of MLT neutral winddata analysis published elsewhere. The present findings provided the first direct evidence,proving that PW play an important role in the physics of midlatitude sporadic E layers.3. Planetary Wave Influence on Sporadic E via Modulation of Atmospheric TidesIn Paper B the investigation of the PW-E s relationship was carried one step further by meansof correlating concurrent mesospheric neutral winds and foEs data from neighboringlocations, in order to understand the physical mechanism behind the PW- E s interaction. Theneutral wind data were hourly means of zonal and meridional winds measured by themedium frequency radar in Saskatoon, Canada (52 o N, 107 o W), and the meteor wind radar inSheffield, UK (52 o N, 2 o W). The wind measurements were compared with available foEsobservations made with ionosondes located as near to the radars as possible, that is, we usedBoulder, Colorado (40 o N, 105 o W) foEs data for the American sector (Saskatoon), andLannion , France (49 o N, 3 o W) data for the West European sector (Sheffield).For the analysis we have used wavelet transform, digital filtering, and corelloperiodogrampower spectral analysis techniques (for details see Paper B). The wavelet spectrograms of thewind data verified that a 7-day PW dominated the spectrum from about day 235 to 265,having amplitudes near 16 m/s for UK and 10-12 m/s for Saskatoon. The Saskatoon recordsshow that above 97 km the PW amplitude tends to decrease with altitude. As discussed in theprevious section the same 7-day periodicity was also present concurrently in the sporadic Ecritical frequency foEs for both stations in Boulder and Lannion.Next, the 7-day (PW) periodicities seen in the meridional wind were compared directly withthose in foEs keeping in mind of course that these variations were measured at differentaltitude. Based on a detailed analysis (see Paper B) we concluded that for the strong PWevent under consideration there was no convincing evidence in favor of a direct PW role onE s generation. This pointed to the possibility for an indirect PW role, probably through themodulation of atmospheric tides. We arrived at this option because of the nonlinear165
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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
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Improving MST radar resolution by u
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latitudes, arguing that the former
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Report on Session I.3 “Winds, Wav
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Turbulence.The session then moved i
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Report on Session I.4 “Meteorolog
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Multiple Antenna Profiling Radar (M
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Report on Session II “Novel Persp
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synchronized by GPS and connected v
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The highly positive response of the
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10th International Workshop on Tech
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10th International Workshop on Tech
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Session I.1: Radar scattering proce
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⎡7800 ∂q⎤(3)⎢ 15500q⎥M =
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Figure 2 compares profiles of ω B
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Figure 1: Data from the MST radar a
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Ri =shear2ωB22⎛ ∂u⎞ ⎛ ∂v
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Meridional (deg)1050−5−10Echo P
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Subarray Configuration, Capon Metho
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Fig. 2 PMSE plot (SOUSY Svalbard Ra
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VHF radar interferometry had shown
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turbulence. From Figures 1 and 2, i
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SummaryFrom the aspect sensitivity
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a specific range. In this work, syn
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P C(dB)(a) Echo Power60504030200.70
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most occidental area of South Ameri
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Quegan, 1992). It should be useful
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measurements, is shown in figure 1(
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The present observations thus empha
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RECENT OBSERVATIONS OF E REGION FIE
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measured spectra in order to separa
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drifts at E and F regions heights b
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• Are characterized by type II ec
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The main parameters that could be o
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THE ROLE OF UNSTABLE SPORADIC-E LAY
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(σ H / σ P )E y (where σ H and
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STUDY OF A LOW E-REGION QUASI-PERIO
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100 m/syrFigure 4: Geometry of the
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Where the notations carry same mean
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Where dx/dt and dy/dt are the veloc
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non-negativity of the image is prio
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spectrum corresponding to the backs
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The Artigas and Machu-Picchu Statio
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Arguments against the second altern
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Extension of the Kolmogorov spectru
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volumeESRvolumeSSRSSR SSRESR ESRSSR
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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
Page 127 and 128: 4. SummaryHere we describe a radio
Page 129 and 130: Figure 1. E-region DPS4 spectra, ri
Page 131 and 132: effects. It is therefore plausible
Page 133 and 134: 1996 and high in 2002). The electri
Page 135 and 136: electric fields map along the geoma
Page 137 and 138: SNR condition is always difficult a
Page 139 and 140: Figure-4 Power spectrum plots of a
Page 141 and 142: As we show below, Jicamarca offers
Page 143 and 144: particularly during daytime counter
Page 145 and 146: where ˆδ nm = (δ l − δ m )
Page 147 and 148: PMSE is more easily interpreted as
Page 149 and 150: ResultsTemperature climatology• s
Page 151 and 152: Simultaneous PMSE and NLC observati
Page 153 and 154: ResultsSeasonal variationMSE are no
Page 155 and 156: Figure 2: MSE parameters as functio
Page 157 and 158: Session I.3: Winds, waves and turbu
Page 159 and 160: poor. It was shown that poor perfor
Page 161 and 162: The use of diffraction pattern simi
Page 163 and 164: F 13 (ξ x ′) = (1 − cos 2ψ N)
Page 165 and 166: Figure 3: (a) Baseline length depen
Page 167 and 168: 3. ResultsFigure 1 shows the amplit
Page 169: variability.Figure 4 shows the aver
Page 173 and 174: the 12-h and 24-h periodicities in
Page 175 and 176: winds and variances at altitudes 70
Page 177 and 178: similar correlation with larger mag
Page 179 and 180: of the refraction index are not equ
Page 181 and 182: Fig. 8. Zonal wind (top) and temper
Page 183 and 184: STUDIES ON ATMOSPHERIC GRAVITY WAVE
Page 185 and 186: 1100-1200 hours. From this plot 6.3
Page 187 and 188: STUDIES ON WINDS AND MOMENTUM FLUXE
Page 189 and 190: 3.4 Monthly variation of momentum f
Page 191 and 192: DEEP PENETRATIVE CONVECTION AND GEN
Page 193 and 194: ly changes direction with time with
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Page 201 and 202: These two last relations are the on
Page 203 and 204: 3.2.1 From v ′2 to ɛ kThe questi
Page 205 and 206: 5.2 Frequency distributionsSeveral
Page 207 and 208: ReferencesAlisse J.-R. and C. Sidi.
Page 209 and 210: Röttger J. and C.H. Liu. Partial r
Page 211 and 212: Specular reflection is negligible f
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Page 217 and 218: this latitude in late April). Surfa
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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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