Effects of Radar Proximity on Single-Doppler Velocity Signatures of Axisymmetric Rotation and Divergence

Wood, Vincent T.; Brown, Rodger A.

doi:10.1175/1520-0493(1992)120<2798:eorpos>2.0.co;2

Cited by 41 publications

(30 citation statements)

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“…In Fig. 16, the inbound-outbound velocity couplet pattern is indicative of pure cyclonic rotation that is symmetrical (e.g., see Wood and Brown 1983;Brown and Wood 1987). The RMW was 6.5 km and had already decreased from a radius of 7.4 km at 0604 UTC in response to the Ç0.5 h of increased convection-latent heat release.…”

Section: March 1996 N O T E S a N D C O R R E S P O N D Ementioning

confidence: 94%

A WSR-88D Radar View of Tropical Cyclone Ed

Stewart¹,

Lyons²

1996

Wea. Forecasting

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The Guam WSR-88D (Weather Surveillance Radar-1988 Doppler) Doppler radar collected reflectivity, Doppler radial velocity, and other information for Supertyphoon Ed as it traversed the northern sections of Guam as a minimal tropical storm on 30 September 1993. This was the first-ever recorded passage of a tropical cyclone over a Next Generation Weather Radar WSR-88D Doppler radar site. Reflectivity data provided valuable information about the location of a precipitation-free ''eye,'' while radial velocity data provided useful information about tropical cyclone wind center location and strength. The velocity data also provided a 3-h lead time to upgrade the tropical cyclone to tropical storm intensity prior to landfall. Forecasters at Andersen Air Force Base used this information to give what turned out to be a very accurate short-range forecast of a brief period of gales with maximum gusts to 26 m s 01 . Land-based surface wind observations correlated extremely well with 75% -80% of the 1500-m radial velocity estimates, which is similar to findings made by Powell and Tanner et al. Additional radar signatures of interest include offsets between the reflectivity center and velocity circulation center, detection of tropical storm and typhoon / hurricane force winds, Doppler velocity maxima within the convective rainbands, and mesocyclonic circulations detected by the WSR-88D's mesocyclone algorithm.Concerning mesocyclones, one was detected very close to the location of the actual wind center when Ed was developing an eye prior to landfall. Within approximately 1 h of initial mesocyclone occurrence, a cyclonic divergent velocity-couplet pattern formed, possibly due to the development of low-level supergradient winds. The observed Doppler velocity patterns were consistent with the lower-tropospheric horizontal wind and vertical motion patterns in and around the eye as described by Malkus, Kuo, and Gray and Shea. After clearing the west coast of Guam, two separate mesocyclones formed just inward of the eyewall and appeared to be ingested into the main eye circulation. Similar findings were obtained from airborne Doppler radar analyses made by Marks and Houze. Shortly thereafter, Ed underwent a period of rapid intensification. In both instances, the mesocyclones appeared to have played a role in eye development and intensification.

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Section: March 1996 N O T E S a N D C O R R E S P O N D Ementioning

confidence: 94%

A WSR-88D Radar View of Tropical Cyclone Ed

Stewart¹,

Lyons²

1996

Wea. Forecasting

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“…As described in Lee and Marks (2000), the GrVTDsimplex method begins with an initial TC center and RMW estimated from the single-Doppler velocity dipole signature (Wood and Brown 1992). To search for a global maximum of the mean tangential winds, an array of 16 initial guess centers surrounding this initial center is conducted for subsequent GrVTD-simplex algorithm and yields 16 different simplex center estimates for a given radius within a range of likely RMWs.…”

Section: ) the Grvtd-simplex Center Findingmentioning

confidence: 99%

“…Wood and Brown (1992) illustrated that the characteristics of a TC approximated by an idealized Rankine vortexincluding its center, radius of maximum wind (RMW), and the maximum wind speed-can be estimated from the location and magnitude of this Doppler velocity dipole. Radial inflow (outflow) near the RMW can be inferred if the aforementioned pattern rotates clockwise (counterclockwise).…”

Section: Introductionmentioning

confidence: 99%

The Gradient Velocity Track Display (GrVTD) Technique for Retrieving Tropical Cyclone Primary Circulation from Aliased Velocities Measured by Single-Doppler Radar

Wang

Zhao

Lee

et al. 2012

Journal of Atmospheric and Oceanic Technology

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The ground-based velocity track display (GBVTD) technique was developed to estimate the primary circulations of landfalling tropical cyclones (TCs) from single-Doppler radar data. However, GBVTD cannot process aliased Doppler velocities, which are often encountered in intense TCs. This study presents a new gradient velocity track display (GrVTD) algorithm that is essentially immune to the Doppler velocity aliasing. GrVTD applies the concept of gradient velocity-azimuth display (GVAD) to the GBVTD method. A GrVTD-simplex algorithm is also developed to accompany GrVTD as a self-sufficient algorithm suite.The results from idealized experiments demonstrate that the circulation center and winds retrieved from GrVTD with aliased velocity and GBVTD with dealiased velocity are in good agreement, but GrVTD is more sensitive to random observation errors. GrVTD was applied to Hurricane Charley (2004) where the majority of the Doppler velocities of the inner-core region were aliased. The GrVTD-retrieved circulation pattern and magnitude are nearly identical to those retrieved in GBVTD with manually dealiased velocities. Overall, the performance of GrVTD is comparable but is more sensitive to the data distribution than that of the original GBVTD using dealiased velocity. GrVTD can be used as a preprocessor for dealiasing velocity in TCs before the data are used in GBVTD or other algorithms.

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“…The time interval between two sequential CAPPIs was confined to 10 to 30 minutes. The datasets in Doppler mode which involved the maximum positive and negative radial velocities were primarily used to derive the position of typhoon centers via the scheme initiated by Wood and Brown (1992). And then the estimated centers were subjectively modified referring to the geometric centers of area enclosed by weaker echoes.…”

Section: Mesoscale Behaviors Of Typhoon Otto Under the Influence Of Tmentioning

confidence: 99%

Doppler Radar Analysis of Typhoon Otto (1998)-Characteristics of Eyewall and Rainbands with and without the Influence of Taiwan Orography

Hor

Wei

Chang

et al. 2005

Journal of the Meteorological Society of Japan

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By using the observational data collected by the C-band Doppler radar which was located at the Green Island off the southeast coast of Taiwan, as well as the offshore island airport and ground weather stations, this article focuses on the mesoscale analysis of inner and outer rainband features of Typhoon Otto (1998), before and after affected by the Central Mountain Range (CMR) which exceeds 3000 m in elevation while the storm was approaching Taiwan in the northwestward movement.While the typhoon was over the open ocean and moved north-northwestward in speed of 15 km/h, its eyewall was not well organized. The rainbands, separated from the inner core region and located at the first and second quadrants relative to the moving direction of typhoon, were embedded with active convections. The vertical cross sections along the radial showed that the outer rainbands tilted outward and were more intense than the inner ones. As the typhoon system gradually propagated to the offshore area near the southeast coast of Taiwan, the semi-elliptic eyewall was built up at the second and third quadrants. Moreover, the strength of the eyewall became more intense compared with the outer rainbands, and the maximum wind axis was quite parallel to the vertical orientation of radar reflectivity in the eyewall. After the detailed streamline analysis, it indicated that the eyewall was enhanced by the confluence between the westerly flow, triggered by the farther outer circulation of the storm around the Taiwan Island, and the northwesterly flow near the inner circulation of the storm itself. Also, the left quadrant in the lower portion (below 2 km in altitude) possessed stronger Doppler velocity than that in the right quadrant, and the upper portion (above 2.0 km) had the opposite mode. This reverse phenomenon of Doppler wind in the lower portion of the typhoon became more pronounced while the storm was getting closer to the mountain. The estimated typhoon center below 1.5 km in altitude had a slower

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Effects of Radar Proximity on Single-Doppler Velocity Signatures of Axisymmetric Rotation and Divergence

Cited by 41 publications

References 0 publications

A WSR-88D Radar View of Tropical Cyclone Ed

A WSR-88D Radar View of Tropical Cyclone Ed

The Gradient Velocity Track Display (GrVTD) Technique for Retrieving Tropical Cyclone Primary Circulation from Aliased Velocities Measured by Single-Doppler Radar

Doppler Radar Analysis of Typhoon Otto (1998)-Characteristics of Eyewall and Rainbands with and without the Influence of Taiwan Orography

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