The signature of mid‐latitude convection observed by VHF wind‐profiling radar

Hooper, David A; McDonald, A. J.; Pavelin, Ed; Carey‐Smith, Trevor; Pascoe, Charlotte

doi:10.1029/2004gl020401

Cited by 23 publications

(27 citation statements)

References 17 publications

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“…This technique was also found to be an effective way of rejecting the clearly-unreliable horizontal wind variations associated with convective activity. Although only clear-air signal components are involved, the associated changes in vertical wind can be more than 1 m s −1 in under a minute (Hooper et al, 2005). This clearly violates the fundamental DBS assumption of a stationary wind field.…”

Section: Exploitation Of Complementary-beam Informationmentioning

confidence: 88%

“…Hooper et al, 2005). The associated rain rates are greater than 5 mm h −1 and the hydrometeor fall speeds can reach almost 10 m s −1 at the lowest observable altitudes.…”

Section: Introductionmentioning

confidence: 95%

“…This is applied by both the v0 and v3 schemes. Vertical beam observations are made every other dwell so that profiles of the vertical wind are available at regular intervals of approximately 47 s. This feature was introduced in order to study the rapidly-varying vertical velocities associated with convection (Hooper et al, 2005). Nevertheless, as will be discussed in Sect.…”

Section: Introductionmentioning

confidence: 99%

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Validation of a new signal processing scheme for the MST radar at Aberystwyth

et al. 2008

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Abstract. This paper describes a new signal processing scheme for the 46.5 MHz Doppler Beam Swinging windprofiling radar at Aberystwyth, in the UK. Although the techniques used are similar to those already described in literature -i.e. the identification of multiple signal components within each spectrum and the use of radial-and time-continuity algorithms for quality-control purposes -it is shown that they must be adapted for the specific meteorological environment above Aberystwyth. In particular they need to take into account the three primary causes of unwanted signals: ground clutter, interference, and Rayleigh scatter from hydrometeors under stratiform precipitation conditions. Attention is also paid to the fact that short-period gravitywave activity can lead to an invalidation of the fundamental assumption of the wind field remaining stationary over the temporal and spatial scales encompassed by a cycle of observation. Methods of identifying and accounting for such conditions are described. The random measurement error associated with horizontal wind components is estimated to be 3.0-4.0 m s −1 for single cycle data. This reduces to 2.0-3.0 m s −1 for data averaged over 30 min. The random measurement error associated with vertical wind components is estimated to be 0.2-0.3 m s −1 . This cannot be reduced by time-averaging as significant natural variability is expected over intervals of just a few minutes under conditions of short-period gravitywave activity.

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Section: Exploitation Of Complementary-beam Informationmentioning

confidence: 88%

“…Hooper et al, 2005). The associated rain rates are greater than 5 mm h −1 and the hydrometeor fall speeds can reach almost 10 m s −1 at the lowest observable altitudes.…”

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Validation of a new signal processing scheme for the MST radar at Aberystwyth

et al. 2008

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“…Observations identified as convective activity at mid-latitudes have previously been discussed in Hooper et al (2005). As indicated in Hooper et al (2005) a number of different signals are generally observed during periods of atmospheric convection, these include large rapidly varying vertical velocities, large values of vertical spectral width and occasionally enhanced signal powers in the upper troposphere. However, unusually during this event large vertical velocity perturbations are also observed above the Correspondence to: A. J.…”

Section: Introductionmentioning

confidence: 95%

Wind-profiler observations of gravity waves produced by convection at mid-latitudes

et al. 2006

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Abstract. This work presents a case study which includes regions of large rapidly varying vertical velocities observed by a VHF wind-profiler at Aberystwyth (52.4 • N, 4.1 • W). Analysis indicates that this region is associated with gravity waves above the tropopause level and simultaneous regions of convective activity below the tropopause level. This case study also suggests that convective activity can be identified effectively by finding periods of large uncertainties on the derived velocities. These regions are hypothesized to be related to regions of small-scale inhomogeneity in the wind field.Examination suggests that the large vertical velocity fluctuations above these convective regions are short period gravity wave packets as expected from theory. In addition the vertical flux of the horizontal momentum associated with the gravity waves also displays the pattern of reversal observed in previous studies.

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“…Problems can arise when hydrometeor returns and clear air returns both contribute to the observed radar return signals. It is only under conditions of very heavy precipitation that the two components, observed by this radar, are distinct (Hooper et al, 2005). It is more common for the components to overlap, if a precipitation signal is observed at all, so that both are identified as belonging to a single signal (McDonald et al, 2004).…”

Section: Instruments and Measurement Strategymentioning

confidence: 97%

VHF signal power suppression in stratiform and convective precipitation

et al. 2006

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Abstract. Previous studies have indicated that VHF clear-air radar return strengths are reduced during periods of precipitation. This study aims to examine whether the type of precipitation, stratiform and convective precipitation types are identified, has any impact on the relationships previously observed and to examine the possible mechanisms which produce this phenomenon. This study uses a combination of UHF and VHF wind-profiler data to define periods associated with stratiform and convective precipitation. This identification is achieved using an algorithm which examines the range squared corrected signal to noise ratio of the UHF returns for a bright band signature for stratiform precipitation. Regions associated with convective rainfall have been defined by identifying regions of enhanced range corrected signal to noise ratio that do not display a bright band structure and that are relatively uniform until a region above the melting layer.This study uses a total of 68 days, which incorporated significant periods of surface rainfall, between 31 August 2000 and 28 February 2002 inclusive from Aberystwyth (52.4 • N, 4.1 • W). Examination suggests that both precipitation types produce similar magnitude reductions in VHF signal power on average. However, the frequency of occurrence of statistically significant reductions in VHF signal power are very different. In the altitude range 2-4 km stratiform precipitation is related to VHF signal suppression approximately 50% of the time while in convective precipitation suppression is observed only 27% of the time. This statistical result suggests that evaporation, which occurs more often in stratiform precipitation, is important in reducing the small-scale irregularities in humidity and thereby the radio refractive index. A detailed case study presented also suggests that evaporation reducing small-scale irregularities in humidity may contribute to the observed VHF signal suppression.

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The signature of mid‐latitude convection observed by VHF wind‐profiling radar

Cited by 23 publications

References 17 publications

Validation of a new signal processing scheme for the MST radar at Aberystwyth

Validation of a new signal processing scheme for the MST radar at Aberystwyth

Wind-profiler observations of gravity waves produced by convection at mid-latitudes

VHF signal power suppression in stratiform and convective precipitation

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