HR: 09:00h
AN: AE31A-04 INVITED     [PDF]
TI: The Severe Thunderstorm Electrification and Precipitation Study (STEPS)
AU: * Rutledge, S A
EM: rutledge@radarmet.atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Ft. Collins, CO 805231372 United States
AU: Lang, T J
EM: tlang@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Ft. Collins, CO 805231372 United States
AB: During May-July 2000, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) was conducted in the High Plains, near the Colorado-Kansas border, in order to achieve a better understanding of the interactions between kinematics, precipitation, and electrification in severe thunderstorms. Specific scientific objectives included: 1) understanding the apparent major differences in precipitation output from supercells that have led to them being classified as low-precipitation (LP), classic or medium-precipitation, and high-precipitation; 2) understanding lightning formation and behavior in storms, and how lightning differs among storm types, particularly to better understand the mechanisms by which storms produce predominantly positive cloud-to-ground (CG) lightning; and 3) to verify and improve microphysical interpretations from polarimetric radar. The project involved the use of a multiple-Doppler and polarimetric radar network, as well as a time-of-arrival VHF lightning mapping system, the T-28 armored research aircraft, electric field meters carried on balloons, mobile mesonet vehicles, instruments to detect and classify transient luminous events over thunderstorms (TLEs; e.g., sprites and blue jets), and mobile atmospheric sounding equipment. The project was a major success, gathering unprecedented data on a wealth of diverse cases, including LP storms, supercells, and mesoscale convective systems, among others. Many of the storms produced mostly positive CG lightning during their lifetimes, and also exhibited unusual electrical structures such as a possibly inverted dipole. The 29 June supercell case has received considerable study to date including the analysis of polarimetric radar data to demonstrate couplings between storm dynamics and the formation of hail and graupel, which lead to formation of significant positive charge in the mid-levels and copious amounts of positive cloud-to-ground lightning. The charge structure in the 29 June case, along with several other STEPS cases, contained charge structures that deviated from the standard tripole charge arrangement. Work is also under way to analyze the MCS event on 11 June, in particular, to better understand the mechanisms leading to positive CG lightning in the trailing stratiform region.
DE: 3304 Atmospheric electricity
DE: 3314 Convective processes
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting