Observations of Ice-Crystal Fallstreaks with Supercooled Liquid Water Generating Heads from the SGP Central Facility
Campbell, J.R.(a), Welton, E.J.(b), Spinhirne, J.D.(c), Starr, D.O'C.(d), and Ferrare, R.A.(e), Science Systems & Applications, Inc. (a), NASA/Goddard Space Flight Center (b-d), NASA Langely Research Center (e)
Thirteenth Atmospheric Radiation Measurement (ARM) Science Team Meeting
On the morning of 31 December 2001, numerous ice-crystal fallstreak clouds with supercooled liquid water (SLW) generating heads were detected in Raman (0.355 m) and Micropulse lidar (MPL, 0.523 m) data collected from the SGP central facility. Though lidar observations of cirrus uncinus streaks (colloquially referred to as mares tails) are not uncommon, their co-incidence with liquid-phase parent clouds is rare. GOES-8 IR images showed that the event was very localized to the area around the central facility and to be short lived overall (~ 2.0 hr). Water vapor imagery and local radiosondes show that the clouds formed in advance of an elevated frontal boundary, and abruptly ended with the passage of the corresponding wave/trough axis. Significant vertical velocities (~ 1.0 m/s) were detected at a nearby NOAA Wind Profiler Network site in advance of the clouds within a confined layer (3.0 6.0 km). The fallstreak shafts extended to nearly 1.5 km below cloud base (5.5 6.0 km), and depolarization ratios detected by the Raman Lidar within the fallstreaks varied between 6.0 12.0%. Temperatures near cloud base ranged from -25.0 to -30.0 C. Our poster documents this paradox event (liquid water cloud begetting ice-phase precipitation) by presenting the many clues/views provided by CART and other local remote sensing. Ultimately we seek to understand what microphysical and dynamic mechanisms were occurring, and explain how SLW droplet growth was able to subsist in the presence of seemingly appreciable ice nucleation.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
