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TROPOPAUSE EROSION BY MOUNTAIN WAVE BREAKINGDavid A Hooper 1 and Ed Pavelin 21 Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK2 Department of Meteorology, University of Reading, PO Box 243, Reading. RG6 6BB, UKIntroductionThe tropopause represents a boundary between air masses with distinct chemical anddynamical properties. Traditionally it has been thought of as a discrete level at which theseproperties change sharply. Although this is often the case, the transition between uppertroposphericand lower-stratospheric characteristics can also be much more gradual (Hooperand Arvelius, 2000). Under such circumstances it is more appropriate to think of thetropopause as a region which can have a vertical extent of up to several kilometres. Thecurrent study demonstrates that turbulent mixing, caused by gravity wave breaking, is one ofthe mechanisms which can lead to a broadening of the tropopause region. A case study ispresented for observations made by the UK Natural Environment Research Council MSTradar at Aberystwyth.Case Study of 18th July 2001MST radar data for the altitude region 8 - 12 km on 18th July 2001 are shown in Figure 1.The crosses superimposed on each panel indicate the altitude of the tropopause derived fromthe vertical beam signal power (top panel) using an objective algorithm (Hooper andArvelius, 2000); a sharpness value (second panel) of 3 corresponds to a definite tropopause(and a narrow tropopause region), a value of 0 to an indefinite tropopause (and a broadregion), and intermediate values to intermediate sharpnesses (and depths of region). As willbe shown shortly, the changes in sharpness are more significant than those of altitude. Thevertical beam radial velocity fluctuations seen between 0600 and 1500 UT (third panel) areattributed to mountain wave activity corresponding to low-level winds (not shown) from thenorth-east (Prichard et al., 1995). Enhanced values of the beam broadening corrected verticalbeam spectral widths (fourth panel) indicate that moderate turbulence coincides with themaximum altitude reached by the mountain wave activity. This is particularly clear at around9.5 km altitude between 0600 and 1100 UT, but can still be seen, to a lesser extent, as themaximum altitude drops from around 9.5 km, at 1330 UT, to below 8 km, at 1500 UT.The fact that the mountain wave activity is not able to propagate beyond the tropopause levelis attributed to critical level absorption in the upper troposphere (Worthington and Thomas,1996). For a mountain wave, a critical level corresponds to an altitude at which thecomponent of the horizontal wind parallel to the low-level (wave generating) wind hasreduced to zero. A mountain wave cannot propagate above a critical level but will dissipateall of its energy at this level through turbulent mixing. It can be seen that the maximumaltitude reached by the mountain wave activity corresponds closely to that at which the windspeed (fifth panel) first drops to zero. The existence of a critical level can be demonstratedmore explicitly by considering the normalised projected wind (sixth panel). This is thenormalised dot product of the wind vector at each level with that at the lowest level observedby the radar (1.7 km), i.e. the cosine of the angle between the wind vectors. The maximumaltitude reached by the mountain wave activity corresponds closely to that at which thisfactor first drops to zero.46
Figure 1: Data from the MST radar at Aberystwyth for 18 th July 2001.Turbulent mixing across a vertical gradient of a conservative passive tracer, such as potentialtemperature or ozone concentration, will generate irregularities of that tracer over acontinuous range of scale sizes. The magnitude of the irregularities will depend on both theinitial vertical gradient of the tracer and on the strength of the turbulence (Ottersten, 1969).However, if turbulent activity continues for a sufficient length of time, the distribution of thetracer is expected to become more homogeneous across the depth of layer, with sharp tracergradients occurring at the layer boundaries (Browning and Watkins, 1970). As might47
Page 1 and 2: MST10Tenth InternationalWORKSHOPOn
Page 3 and 4: MST 10 Group PictureMay 15 th , 200
Page 5 and 6: TENTH INTERNATIONAL WORKSHOP ON TEC
Page 7 and 8: Table of ContentsPREFACE ..........
Page 9 and 10: I.2.18 FURTHER OBSERVATIONS OF PMSE
Page 11 and 12: I.3.27 NEW MST RADAR METHODS FOR ME
Page 13 and 14: I.4.19 STUDY OF A MESOSCALE LAND-TO
Page 15 and 16: I.5.502 AN ATTEMPT TO CALIBRATE THE
Page 17 and 18: PrefaceMST10The Tenth International
Page 19 and 20: and the local organizing committee,
Page 21 and 22: The operational aspects and recent
Page 23 and 24: 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: Figure 2 compares profiles of ω B
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 and 76: Quegan, 1992). It should be useful
Page 77 and 78: measurements, is shown in figure 1(
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
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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
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Anomalous spectraTalkner [4] studie
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To observe the E region FAI echoes,
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matter daytime or nighttime and are
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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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