Wednesday, 30 April 2008: 9:30 AM
Palms I (Wyndham Orlando Resort)
The Quasi-Biennial Oscillation (QBO), i.e., a 24-30 month oscillation of the equatorial zonal winds in the lower stratosphere, has been postulated to influence deep convection (and thus lightning production) via changes in tropopause height, upper-tropospheric to lower-stratospheric wind shear, and upper-tropospheric vorticity. This study follows the methodology of Collimore et al. (2003) but focuses on identifying changes in lightning flash density magnitude and patterns rather than OLR and highly reflective clouds to determine regions of enhanced convection. Eight years (1998-2005) of Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) observations are composited by NCEP reanalysis tropopause temperatures and 50-200hPa zonal winds to study the modulation of lightning by tropopause height and upper-tropospheric to lower-stratospheric shear variations during the east and west phases of the QBO. The comparison of flash density, shear, and tropopause height difference distributions indicate that an increase (decrease) in flash density is associated with weaker (stronger) shear and a higher/cooler (lower/warmer) tropopause. However, this relationship does not hold for all regions. Variations in stratiform and convective precipitation characteristics observed by the TRMM Precipitation Radar (PR) during the east and west phases of the QBO will also be explored.
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