Lightning and other electrical observations in STEPS

The Severe Thunderstorm Electrification and Precipitation Studies (STEPS) field program, May 22 – July 16, 2000, provided a wide range of meteorological and electrical observations for studies to gain a better understanding of the interactions between kinematics, precipitation production, and electrification in severe thunderstorms on the High Plains. STEPS had three main themes, (1) precipitation formation, (2) electrification and lightning and (3) hydrometeor identification by polarimetric radar, that are closely related. Thus, combining all three themes in one program provided economies and is fostering fruitful cross-disciplinary interactions. This paper will concentrate on the electrification and lightning theme. The following are the goals for this theme in STEPS:

1. 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.

2. To understand the initiation and development of individual lightning flashes as a function of storm evolution and storm electrification, particularly for severe storms.

3. To understand the influence of precipitation formation on electrical development, especially in those storms producing large hail.

4. To improve microphysical and electrical parameterizations in numerical models of deep convection through intercomparisons of dual-polarimetric radar measurements and comparisons of these with aircraft and ground-based observations of precipitation types and electrical properties.

Measurements of electrical storm properties in STEPS included three-dimensional lightning mapping by New Mexico Institute of Mining and Technology, balloon soundings by the National Severe Storms Laboratory and University of Oklahoma to measure electric fields inside storms, and electric field and microphysical measurements by the T-28 aircraft from South Dakota School of Mines and Technology. These data are being analyzed in conjunction with data from the Doppler and polarimetric radars that are discussed in a previous paper. This paper will discuss the lightning and electric field instrumentation and will show some examples of data from these instruments during STEPS.