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VHF RADAR REFLECTIVITY, VERTICAL VELOCITIES ANDRAINFALL RATE DURING TYPHOON PASSAGES OVER TAIWANC.J. Pan 1 , M.L. Hsu 1 , L.J. Chung 1 , J. Röttger 2,1 and J. Wu 11 Institute of Space Science, National Central University, Chung-Li, Taiwan2Max-Planck-Institut, 37191 Katlenburg-Lindau, GermanyThe Chung-Li VHF radar, located in northern Taiwan, was operated in September and October2001 to study the radar reflectivity and wind field changes during the approach, passage anddeparture of typhoons. The reflectivity is given by humidity and temperature changes eithercaused by turbulence or by stable layering. Additionally the radar observes mean and turbulentvelocities. Other than weather radars, the VHF radars obtain the vertical profile of theseparameters over a fixed location. Besides measuring the horizontal wind, they are particularlysuited to measure the reflectivity and the vertical velocity component. Typhoon studies had alsobeen done earlier with VHF radars (e.g., Röttger et al., 1991; Shibagaki et al., 2003).The Chung-Li VHF Radar is a stratosphere-troposphere (ST) radar operating on 52 MHz withpeak power of 80 kW and an antenna array of 192 Yagis separated into three antenna arrays forreceiving in the spaced antenna mode. For the presented typhoon observations the antennas werepointed vertically. The height resolution was 300 m, and 102 ms coherent integration time wasapplied, which corresponds to a maximum resolvable radial velocity of 14.4 m/s. One recordincluded 256 data points, which were analyzed with the complex auto-covariance method,yielding the radar echo power (from which we deduced the relative reflectivity), the mean radialvelocity (which we assumed to represent a reasonable estimate of the vertical velocity) and theturbulent velocity for dwell times of 29 s. This method is very robust with respect to low signalto-noiseratios, which usually characterize echoes from the upper parts of the observable range upto 10 km. The determination of the horizontal velocity with the spaced antenna method will beperformed in a later study. Here we concentrate on reflectivity and vertical velocity and someprecipitation observations during passages of three typhoons.Two days of VHF radarobservations oftyphoon Nari, which broughttorrential rain and large damageto the island of Taiwanin September 2001Radial velocity in vertical beam19.09.01 20.09.01Reflectivity in vertical beamFig. 1 Typhoon Nari having passed Taiwan on 20 Sep. 2001VHF radar reflectivity and velocity in vertical beam274
Typhoon LekimaFig. 2 Typhoon Lekima passing Taiwan on 28 September 2001VHF radar reflectivity and velocity in vertical beamAfter two days of operation during the departure of typhoon Nari (Fig. 1) the Chung-Li VHFradar was operated continuously over about 130 hours between 24 September 2001, 14 LT(UTC+8), and 30 September 2001, 02 LT, with two short interruptions. Fig. 2 shows the radarobservations and a map with track of the eye of typhoon Lekima and the location of the Chung-LiVHF Radar. This figure shows the radar reflectivity (lower panel) and mean vertical velocity(upper panel) during this period. On 24 September the eye was about 800 km south of the radar.During this time the troposphere up to about 10 km altitude showed a very enhanced reflectivity,where a separate layer even moved upward to 12 km altitude. The typhoon moved northward thefollowing day and the reflectivity decreased but the convective activity increased. The latter canbe seen in the almost vertical streaks of upward motion (green) at time scales of less than a fewhours, which are dominating against the downward motions (red). On 25 and 26 September,when the typhoon moved further towards the island several broader layers of reflectivity movedupward to the 10 km level. They comprise boundaries of different air. Since they are separated bysome 4 -12 hours, they could be attributed to meso-scale disturbances embedded in the largerscaletyphoon circulation system. Those meso-scale structures can also be seen in the satellitecloud structure records. The reflectivity layer at constant height of about 6-7 km is close to themelting layer where precipitation was formed. We assume that it results from temperaturegradients occurring in such conditions. On 26-27 September precipitation can be recognized inthe velocity plot as an increase of the downward velocity. Between 6 and 7 km the scatter signalfrom precipitation dominates the velocity estimate, which therefore is biased downward (due tothe falling hydrometeors, which scatter the radar signal). We checked the Doppler spectracarefully and notice that only in the regions of strong downward velocity (red) around 7 km thegiven estimate is not representing the vertical air velocity. Thus, on 26-27 September the upwardstreaks above this altitude are clearly showing many events of deep convection. These werereaching altitudes as high as 12 km.In the second part of 27 September, when the typhoon had its closest distance to the radarlocation the mean vertical velocity was fairly small without indications of convection and thereflectivity showed mostly short living layers. When the typhoon was departing, strong275
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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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Page 231 and 232: Incoherent scatter spectracompared
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Page 235 and 236: Figure 1. Diurnal variation of Turb
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Page 243 and 244: The main recently assumed mechanism
Page 245 and 246: Figure 2. Statistics of numbers of
Page 247 and 248: LIDAR OBSERVATIONS OF MIDDLE ATMOSP
Page 249 and 250: latitudinal dependence of the seaso
Page 251 and 252: APPLICATION OF THE DUAL-BEAMWIDTH M
Page 253 and 254: Figure 2: Mean zonal and meridional
Page 255 and 256: JLKLLK/ILIL6II/G/II/G/LEODFLK/LO/DD
Page 257 and 258: The monthly diurnal mean of horizon
Page 259 and 260: Session I.4: Meteorological Phenome
Page 261 and 262: Integration of the VHF wind profile
Page 263 and 264: Figure 1 : Map of the Lago Maggiore
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Page 267 and 268: Eyewall(a)(b)(c)(d)Fig. 3: Radius-h
Page 269 and 270: as low as 0.55. The Piura 50-MHz ra
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Page 273 and 274: • Period 1 (June 1-10): SCCs exis
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Page 283 and 284: Fig. 5 Passage of typhoon Hayan on
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Page 287 and 288: 22 June 2000 23:22:23 - 23:24:20 at
Page 289 and 290: the time-height section of a convec
Page 291 and 292: Thurai, M., T.Iguchi,T. Kozu, J.D.E
Page 293 and 294: There are two main mechanisms which
Page 295 and 296: Horel, J.D. and Cornejo-Garrido, A.
Page 297 and 298: estimating two independent and redu
Page 299 and 300: RASS THETA (K) RASS v-component (m/
Page 301 and 302: Surface winds usually range from 10
Page 303 and 304: weak (maximum of 5 m s -1 ) and the
Page 305 and 306: The vertical component from the VTB
Page 307 and 308: Figure 8 shows the profile of virtu
Page 309 and 310: 2 3D ( , ) ( ) ( ) ˆ ( ) ˆp∆ xm
Page 311 and 312: presented in Praskovsky et al. (200
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
Page 317 and 318: Figure 1: composite day (13 days) o
Page 319 and 320: virtual sensible heat fluxes ( Wm-2
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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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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