The June 22 tropical squall line observed during COPT 81 experiment: Electrical signature associated with dynamical structure and precipitation

Abstract

The tropical convection experiment COPT 81 (Convection Profonde Tropicale) was carried out near Korhogo (Northern Ivory Coast) during May and June 1981. The June 22 squall line was observed using meteorological and electrical equipment. The frontal part was characterized by a heavy precipitation core associated with strong convection. It was followed by a region of weak precipitation and a wide area of stratiform rain. The characteristic of this squall line resides in the two‐dimensional structure of the observed three‐dimensional wind fields, with intense convection ahead of the heavy precipitation core. Electrical measurements indicate that electrostatic field changes, at ground level, occurred in the weak precipitation zone and in the stratiform precipitation region. No particular electrical activity was observed in the most convective but shallow part of the squall line. A classical dipole structure appeared within the stratiform area. The stationary electrical structure was coherent with the stationary dynamics and precipitation pattern of the squall line.

Hydrometeor mass, number, and space charge distribution in a “Hector” squall line

“…Mixtures of ice crystals and graupel in a thick anvil have been modeled by Leary and Houze [1979]; however, in the ''Hector'' anvils there were no reports of snowflake formation. The observed surface electric field profile during the passage of the ''Hector'' squall is similar to that observed with COPT 81 squall lines which were four times more intense than the ''Hector'' [Chauzy et al, 1985].…”

Charge Structure and Dynamics in Thunderstorms

“…All these features make the electrical structure of midlatitude MCS stratiform clouds potentially complex. (Balloon measurements in Africa, made by Chauzy et al (1985), have confirmed this complexity for tropical MCSs, as well.) MCS stratiform region charge structure has been of interest since early studies (e.g., Marshall and Rust 1993) showed that very large amounts of charge reside in these clouds, particularly in a strong charge layer (estimated at 20,000 C) that is often found near the melting level.…”

“…Airborne studies of thunderstorm electrical parameters have made use of instrumented airplanes, rockets, and balloons (e.g., Weinheimer et al 1991;Mo et al 2003;Winn and Moore 1971;Willett et al 1993;Winn et al 1978;Chauzy et al 1985;Byrne et al 1989). Because balloon-borne electrical measurements are relatively simple and inexpensive to acquire, such observations have become the most prevalent in situ data available across different types of thunderstorm clouds.…”

Measurements of Atmospheric Electricity Aloft

“…The electrical structure of SPRs have been investigated by Chauzy et al (1985); Schuur et al (1991); Hunter et al (1992); Marshal and Rust (1993); Stolzenberg et al (1994); Shepherd et al (1996) and Mo et al (2003), all using the balloon borne Electric Field Meter developed by Winn et al (1978) and described in section 6.1.2. From the analysis of many of these balloon soundings, Marshall and Rust (1993) found that vertical electric field structures fell into two distinct categories -Type A and Type B, and that comparison of electric field soundings from several different storms in the same type showed remarkable similarities between charge regions, whose spacing and depth was almost identical between different storms.…”