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STUDIES ON MOMENTUM FLUXES USING MST RADAR WINDSOBSERVED AT GADANKI (13.5°N, 79.2° E), INDIAD. Narayana Rao 1 , I.V. Subba Reddy 2 , P. Kishore 3 , S.P. Namboothiri 3 , K. Igarashi 3 ,K. Krishna Reddy 4 and S.V. Bhaskara Rao 3 .1 National MST Radar Facility, P.B. No.: 123, Tirupati – 517 502, India2 Department of Physics, Sri Venkateswara University, Tirupati - 517 502, India3 Communications Research Laboratory, 4-2-1 Nukui-kita machi, Kognei-shi Tokyo 184-8795, Japan4 Yokohama Institute of Earth Sciences, Frontier Observational Research System for Global Change(FORSGC), 3173-25, Showa-Machi, Kanazawa – KU, Yokohama, Kanagawa – 236-0001, JapanABSTRACTVHF Doppler radars provide a unique database to estimate vertical flux of horizontal momentumin the troposphere and lower stratosphere. Estimation of the oblique momentum flux involves two methods:1) using three beams – one vertical and two oblique, and 2) using four beams – two pairs of oblique beamssystematically offset from the vertical. The rapid steerability of the Indian MST radar allows to make three –and four beam measurements simultaneously. The momentum fluxes measured by the two methods arealmost the same for wind fluctuations in a fairly long period range (longer than 5 h). We choose frequencybands corresponding to periods of 30 min-2h, 2-8 h, 2-16h and 2-24 h. Vertical profiles of the zonal andMeridional flux in each frequency band were found to be consistent, in general, with the total flux. Zonalfluxes were small at lower levels and increasingly negative ( westward) at higher heights. The dominantcontributions to the Meridional flux occur in the lower-frequency band.IntroductionThe importance of gravity wave effects on various dynamical processes has been welldocumented in the upper and middle atmosphere. However, less is known about these waves in thethe lower atmosphere especially in tropics. The upward propagating gravity waves transport energyand momentum in different regions of the atmosphere along with their propagation to produceeffects at upper heights [Hines, 1972] indicated that the influence of such waves at upper heightsmight be significant. Most of the theoretical and modeling studies were primarily concentrated onthe effect of gravity waves in the mesosphere and thermosphere, but later it has been found thatthese effects are also important in the troposphere and stratosphere. In early observations it isidentified that for lower heights, the momentum divergence caused by mountain waves [Newton,1971], and the importance of such divergence in the evolution of the general circulation wasemphasized by Lilly [1972]. Furthermore, the lack of height coverage at a given time in aircraftflights is a limitation. Vincent and Reid (1983) presented a technique in which ground-based radarscan be used to measure fluxes directly and this technique has been applied to both mesosphericheights [Vincent and Fritts, 1987; Tsuda et al., 1990] and tropospheric and lower stratosphericlevels [Fritts et al., 1990; Thomas et al ., 1992]. Because of the continuous operation of multipleinstruments, long term studies have been conducted to quantify the variability and latitudinaldifference of gravity wave activity [e.g. Vincent and Fritts, 1987; Manson and Meek, 1993;Vincent, 1994]. It has been found that from theoretical and observational studies that the highfrequency gravity waves with small horizontal scales are the majority carriers of momentum. ~70 %of the momentum and the associated zonal drag is due to gravity waves with observed periods lessthan one hour [Fritts and Vincent, 1987]. Chang et al., [1997] used ST radar data from ChristmasIsland to study tropospheric gravity waves and they found a broad range of frequency associatedwith gravity wave activity in the troposphere. A method of Vincent and Reid [1983] is used toestimate the vertical flux of zonal and meridional momentum fluxes from the radial velocities intwo orthogonal beams measured by the Indian MST Radar at Gadanki (13.48º N, 79.18º E) ispresented. These flux values are quite well with the values obtained from previous observations.342
The purpose of this study is to examine Zonal and Meridional fluxes and their variation with bothheight and wave periods, and also to compare fluxes for three and four beam methods.Data BaseIn the present study a VHF Radar at Gadanki (13.48º N, 79.18º E) a tropical station isused to study the gravity wave momentum fluxes in different seasons namely Pre Monsoon (March- May), Monsoon (June - September), Post Monsoon (October - November) and Winter (December-February) seasons. Data is collected continuously for three days in a typical month representing as aseason at 1000 -1600 LT, 2000 – 2030 LT, 0030 – 0100 LT, and 0500 – 0530 LT on each day. Theobservations are taken during 16-19 October 2000, 09-12 April 2001, 16-19 July 2001, 22-25January 2002.Results and DiscussionsIn Figure 1 upper panel shows mean zonal and meridional momentum flux and variance ofwind fluctuations around the mean values during post monsoon season using MST Radar. Theaveraging is made for 3 days i.e.,16- 18 October 2000, for the entire observational period i.e., from1000-1600 LT in each day. Lower panel is the same as above during 09-11 April 2001 representedas during pre monsoon season. All quantities except vertical wind variance are obtained by the fourbeam methods. The positive values of Zonal momentum fluxes indicate Eastward transport ofmomentum and negative values of Zonal momentum fluxes show westward transport ofmomentum. Zonal momentum flux was eastward from 5.5-12.5 km, westward from 12.5-15.5 km.eastward from 15.5 – 18 km and westward above 18 km. This represents that there is a systematicchange in the zonal momentum flux. While going to higher altitudes the magnitude of the zonalmomentum flux is increasing either eastward or westward, this represents that the waves areassumed to be generated in the lower part of the atmosphere and upward propagating waves aredominating and westward momentum fluxes are maximum ~ -0.6 m 2 /s 2 . The positive values ofmeridional momentum fluxes indicate northward transport of momentum and negative values showsouthward transport of momentum. During post monsoon season meridional momentum flux isnorthward from 5 km to 20 km altitude ( +0.4 m 2 /s 2 ). The zonal variance is more than themeridional variance in the altitude range of 12-17.5 km. The lower panel in figure 1 ( during premonsoon season) shows east ward momentum flux (+0.6 m 2 /s 2 ) which is dominating rather than thewestward momentum flux (-0.45 m 2 /s 2 ). The meridional momentum flux is southward and its valueis maximum (-6.5 m 2 /s 2 ) around 11-12 km. In the lower heights up to 10 km the zonal andmeridional variances are small and above 10 km the variances are large.Figure 2 is similar as figure 1 but for monsoon season (upper panel) and winter season(lower panel). In upper panel zonal momentum flux is almost westward, indicating that the westward fluctuations are more rather than the eastward. The meridional momentum flux is southwardup to 7 km, 7- 8.5 km northward, 8.5 - 14.5 km southward and above 14.5 km it is northward. Thezonal and meridional variances are small up to 12 km and above 12 km these variances areincreasing with increasing height. Lower panel in figure 2 shows east ward momentum flux up to 7km from 7-11.3 km westward and above 11.3 km it is eastward. The meridional momentum flux isnorthward up to 11 km, southward 11-13 km, northward from 13 – 17 km and southward from 17-19.5 km. Zonal and meridional variances are high above 13 km indicating that the wave activity ismore prominent.Figure 3 shows zonal and meridional momentum flux, calculated using four beam and threebeam method during different seasons. Three and four beam method calculated zonal andmeridional momentum fluxes agree within error bars both in magnitude and trend. During monsoonseason some discrepancy has been observed above 16 km. This may lead to anisotropy of thebackscatters in the atmosphere. During pre monsoon season some discrepancy has been observedbelow 10 km in meridional momentum flux.Figure 4 shows vertical profiles of zonal and meridional momentum flux profilesdetermined by the fourbeam method with different frequency bands in different seasons viz., pre-343
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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
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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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Page 307 and 308: Figure 8 shows the profile of virtu
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Page 313 and 314: In Fig. 2 a sketch of a mountain le
Page 315 and 316: In Fig. 8 the lamina is aligned on
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Page 321 and 322: 3. Characteristics of precipitation
Page 323 and 324: Fig. 3: Horizontal distribution of
Page 325 and 326: 3. Results and discussionUHF profil
Page 327 and 328: Figure 4. Monthly variation of slop
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Page 333 and 334: Histogram of Zonal Velocityh=5.13 K
Page 335 and 336: 5. Summary of results and concludin
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Page 339 and 340: Boundary layer height, km32.521.5(a
Page 341 and 342: Figure 1:Data from the MST radar at
Page 343 and 344: spectral processing. In this partic
Page 345 and 346: 3. Results and discussionIn the pre
Page 347: 4. SummaryAn attempt has been made
Page 351 and 352: Figure1. Three-day average of momen
Page 353 and 354: 3. The improved method to estimate
Page 355 and 356: But in case of period until 1800 UT
Page 357 and 358: Session I.5: Operational Aspects an
Page 359 and 360: The profilers of WINDAS weredesigne
Page 361 and 362: NOAA, 1994 : Wind profiler assessme
Page 363 and 364: FIRST RESULTS OF THE BOUNDARY LAYER
Page 365 and 366: Figure 3. Pulse Design Diagram to s
Page 367 and 368: MOVEABLE UHF/S-BAND PROFILER/DISDRO
Page 369 and 370: one-minute Z values determined from
Page 371 and 372: TOWARD A MULTISENSOR GROUND BASED R
Page 373 and 374: 3. Cloud Evolution Case StudyOn the
Page 375 and 376: DEVELOPMENT OF A DIGITAL RECEIVER F
Page 377 and 378: Experiment 1 Experiment 2IPP 999Km
Page 379 and 380: ELECTRONIC DIGITAL BEAMFORMING IMPL
Page 381 and 382: The main element of the unit (figur
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Page 389 and 390: Table 2: Experiment #1 results, Tra
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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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