Recorded presentation9.5
Case studies of widespread turbulence in the vicinity of mesoscale convective systems using 13-km RUC analyses
Stanley B. Trier, NCAR, Boulder, CO; and R. D. Sharman and R. G. Fovell
Mechanisms and environmental precursors to widespread turbulence near mesoscale convective systems (MCSs) are being investigated for multiple cases using 13-km RUC analyses. The emphasis in this study is on convectively-generated circulation features that support turbulence outside of clouds. Low Richardson numbers Ri~1 near flight levels in the upper troposphere have been diagnosed using the RUC output. In most cases the turbulence reports occurred near the anvil cloud edge of large MCSs, but as much as 100 to 300 km away from any active deep convection as determined from radar. In these cases, the RUC analyses indicated 20 to 30 m/s increases in upper-tropospheric winds, which appear to be associated with the anticyclonic MCS outflow augmenting the moderately strong environmental flow that existed prior to MCS organization. The strengthening of the upper tropospheric/lower stratospheric flow results in large increases in vertical shear and corresponding low Ri that supports turbulence over broad mesoscale regions. The proposed presentation will also discuss results from convection-resolving numerical simulations employed to better understand the mechanisms by which MCSs alter their environment and produce turbulence.
Session 9, Turbulence and Wind Shear Part I
Wednesday, 23 January 2008, 4:00 PM-5:30 PM, 226-227
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