An overview of the Severe Thunderstorm Electrification and Precipitation Study (STEPS)

The STEPS field program will be conducted in Eastern Colorado and Western Kansas from 22 May to 16 July 2000. The broad goal of STEPS is to achieve a better understanding of the interactions between kinematics, precipitation production, and electrification in severe thunderstorms on the High Plains. The specific scientific objectives include:

1. To understand the apparent major differences in storm processes that have led supercells to be considered as either low, medium (also referred to as classic) or heavy precipitation (LP, MP, and HP) producers.
2. To understand how observed differences in the distribution of precipitation and cloud particles in different types of severe storms cause systematic differences in the way these storms electrify and in the types and rates of intracloud and cloud-to-ground lightning that are produced.
3. To verify and/or to improve inferences of precipitation type from polarimetric radar measurements.

The primary instrumentation includes the NCAR S-Pol, CSU Chill and the NWS Goodland WSR-88D radars for multiparameter and Doppler wind observations, the South Dakota School of Mines and Technology T28 armored aircraft for in situ microphysical observations within storm updrafts, a three dimensional lightning mapping system from the New Mexico Institute of Mining and Technology, balloon-borne electrification measurements and mobile mesonets from the National Severe Storms Lab, and two mobile sounding units from NCAR. In this presentation, we will review the scientific motivation for the STEPS program and summarize the range of datasets obtained during the field phase. This talk will especially emphasize the precipitation studies aimed at understanding the differences between LP, Classic, and HP supercells.