EOL Seminar Series - Jeff Stith (EOL/RAF)

Ice particles in the upper anvil regions of mid-latitude continental thunderstorms during the DC3 program

Jeff Stith
Research Aviation Facility, Earth Observing Laboratory

The morphology of frozen-drop aggregates in thunderstorm anvils from the US Midwest and the environmental conditions where they are found in the upper anvil will be described. In situ airborne data collected in anvils using several particle imaging and sizing probes and bulk total water instrumentation during the 2012 Deep Convective Clouds and Chemistry Experiment (DC3) are described.   Chains of frozen drops have been only rarely reported before and are hypothesized to aggregate due to electrical forces in the clouds.  The evidence for this hypothesis and alternative evidence for low-density frozen drop aggregates in the anvil is examined.    We have identified frozen-drop aggregates in nine of the DC3 anvil cases examined to-date, suggesting that they are common features in these Midwestern anvils.  High concentrations of individual frozen droplets occurred on the tops and edges of one particular set of anvils, while regions closer to the center and bottom of these anvils exhibited fewer frozen drops and more frozen-drop aggregates.  Bulk ice water content measurements across these anvils could only be explained by contributions from both small particles (frozen droplets) and large particles (large aggregates of frozen droplets).    Dual Doppler radar analysis confirmed the presence of deep and strong (>15 m s-1) updrafts and Lightning Mapping Array (LMA) data confirm high electrical activity in the parent cloud of one of the FDA-containing anvils.  These features contrast with previous anvil measurements in tropical/maritime anvils that evidently do not exhibit the same frequency of frozen-drop aggregates.

Tuesday, 12 August 2014, 3:30pm
NCAR Foothills Laboratory
3450 Mitchell Lane
FL2 Large Auditorium (FL2-1022)

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Thursday, August 7, 2014
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Tuesday, August 12, 2014