Estimating Large-Scale Vorticity Using VAD Products and Reflectivity

Lu, Yinghui; Doviak, Richard J.; Crisp, Charlie A.

doi:10.1175/1520-0426(1996)013<1129:elsvuv>2.0.co;2

Cited by 3 publications

(4 citation statements)

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“…Unlike dual-Doppler analysis, this technique samples the entire MCS but becomes unreliable when the echoes are very transient or when the precipitation is stratiform. A well-defined midlevel mesoscale cyclonic vortex did not form as the MCS matured, but the profile of mesoscale vertical vorticity, estimated by means of the TREC method, as well as by a semi-Lagrangian advection technique within the VAD circles (Lu et al 1996), appears to have been cyclonic below 6-7 km and anticyclonic aloft. A positive potential vorticity anomaly existed at midlevels (3-6 km) within the MCS, and potential vorticity increased in strength and in depth during the development of the MCS.…”

Section: Discussionmentioning

confidence: 98%

“…A second technique uses the VAD-derived velocities and its kinematic components (Figs. 7c,d) to estimate the profile of vertical vorticity that best approximates the observed movement of echo patterns within the VAD circle (Lu et al 1996).…”

Section: Mesoscale Flow and Vorticitymentioning

confidence: 99%

“…15. Time-height sections of the mesoscale vertical vorticity (10 Ϫ4 s Ϫ1 ), as estimated by means of (a) the TREC technique; and (b) the method of Lu et al (1996). The zero line is bold, and areas of significant cyclonic (anticyclonic) vorticity are shaded (hatched).…”

Section: A Storm-relative Mesoscale Motionsmentioning

confidence: 99%

“…7), and the vorticity is unknown. A basic assumption (and the same as that used in TREC) of this iterative technique (Lu et al 1996) is that the reflectivity within the VAD circles is conserved from one radar volume to the next. The two results are expected to vary not just because they are based on different techniques, but also because the domain differs.…”

Section: B Mesoscale Relative Vorticitymentioning

confidence: 99%

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Analysis of a Small, Vigorous Mesoscale Convective System in a Low-Shear Environment. Part II: Evolution of the Stratiform Precipitation and Mesoscale Flows

Knupp¹,

Geerts²,

Tuttle³

1998

Mon. Wea. Rev.

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The evolution of the mesoscale flow and precipitation distribution are investigated for a small mesoscale convective system (MCS) that evolved in a nearly barotropic environment exhibiting moderate instability and weak wind shear. Observations primarily from a single Doppler radar detail the growth of the MCS from the merger of several clusters and lines of vigorous convective cells into a mature state consisting of a weaker convective line trailed by an expanding stratiform precipitation region. Analysis of radar reflectivity reveals that this stratiform region formed in situ in the presence of weak mesoscale updraft as decaying convective cores coalesced, rather than through rearward advection of ice particles directly from the convective region. In the absence of sufficient low-level shear, the MCS collapsed rapidly as it assumed the structure of the archetypal convective line and trailing stratiform precipitation region. Velocity-azimuth displays reveal mesoscale updrafts of about 70 cm s Ϫ1 during the active convective stage. In the mature stratiform region, the lower-tropospheric mesoscale downdraft (ϳ40 cm s Ϫ1) exceeded the mesoscale updraft (ϳ10 cm s Ϫ1) above it, and the level separating the two was relatively high at 6.5 km, about 2 km above the 0ЊC level. As the MCS cloud-top anvil area colder than Ϫ52ЊC peaked near 60 000 km 2 , the cloud top descended at rates of 20-40 cm s Ϫ1 despite weak but sustained mesoscale updraft within the upper part of the cloud. A rear inflow jet was observed before convective activity peaked, remained strong while the deep convection diminished, and became the main flow feature as the MCS decayed. This jet subsided from approximately 7 km at the rear end to near the surface at the leading edge of the convection. A weaker ascending front-to-rear current was found above this rear inflow jet. No midlevel mesoscale cyclonic vortex was apparent in the echo structure of the maturing MCS. Indirect estimates of mesoscale vorticity, based on Lagrangian conservation of radar reflectivity, indicate that cyclonic rotation was present in the mesoscale downdraft region, and anticyclonic rotation occurred aloft. The magnitude of this vorticity is about half the Coriolis parameter. A positive potential vorticity anomaly is found at midlevels within the MCS, and this anomaly intensifies in depth and in strength as the system matures. This growth is consistent with the diabatic heating profile estimated from a 1D cloud model.

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Section: Discussionmentioning

confidence: 98%

Section: Mesoscale Flow and Vorticitymentioning

confidence: 99%

Section: A Storm-relative Mesoscale Motionsmentioning

confidence: 99%

Section: B Mesoscale Relative Vorticitymentioning

confidence: 99%

See 2 more Smart Citations

Analysis of a Small, Vigorous Mesoscale Convective System in a Low-Shear Environment. Part II: Evolution of the Stratiform Precipitation and Mesoscale Flows

Knupp¹,

Geerts²,

Tuttle³

1998

Mon. Wea. Rev.

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Statewide Monitoring of the Mesoscale Environment: A Technical Update on the Oklahoma Mesonet

McPherson

Fiebrich

Crawford

et al. 2007

Journal of Atmospheric and Oceanic Technology

440

355

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Established as a multipurpose network, the Oklahoma Mesonet operates more than 110 surface observing stations that send data every 5 min to an operations center for data quality assurance, product generation, and dissemination. Quality-assured data are available within 5 min of the observation time. Since 1994, the Oklahoma Mesonet has collected 3.5 billion weather and soil observations and produced millions of decision-making products for its customers.

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The Fluctuation of Aerosol Number Concentration by Wind Field Variation during Snowfall at the Southwestern Coastal Area

Lee¹,

Kang²,

Seo³

et al. 2008

Journal of the Environmental Sciences

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Estimating Large-Scale Vorticity Using VAD Products and Reflectivity

Cited by 3 publications

References 0 publications

Analysis of a Small, Vigorous Mesoscale Convective System in a Low-Shear Environment. Part II: Evolution of the Stratiform Precipitation and Mesoscale Flows

Analysis of a Small, Vigorous Mesoscale Convective System in a Low-Shear Environment. Part II: Evolution of the Stratiform Precipitation and Mesoscale Flows

Statewide Monitoring of the Mesoscale Environment: A Technical Update on the Oklahoma Mesonet

The Fluctuation of Aerosol Number Concentration by Wind Field Variation during Snowfall at the Southwestern Coastal Area

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