Airborne and ground‐based studies of thunderstorms in the vicinity of Langmuir Laboratory

Abstract

SUMMARYFlights through the central regions of thunderstorms were made over New Mexico on 6 and 15 August I977 with the ONR/NMIMT Schweitzer aeroplane which carried equipment designed to measure all three components of the electric field, and the charge, Q, and diameter, d, of individual precipitation elements. On the earlier day, information was also obtained with : a rain-gaugenetworksurrounding Langmuir Laboratory; a 3 cm radar; an acoustic system for locating lightning channels; a ground-based field-change meter.The first cell on 6 August produced precipitation at the ground but no lightning. Vertical fields, E,, of up to about 50 kVm-' and precipitation charge densities pp of up to -0.5Cwere recorded within the cloud. The second cell, which grew as the first one decayed, produced 7 lightning strokes in 9 minutes during which time the radar revealed vigorous vertical growth in a narrow zone containing precipitation.Thunder reconstructions showed the acoustic sources for the first flash of this cell to be very near the top of the cloud at an altitude of 10 km a d . The subsequent flashes produced acoustic signals from progressively lower in the cloud. When the radar echo reached its maximum height lightning activity ceased. E. values of up to about SOkVm-' and pp values of down to -1 C km-3 were measured.pp was consistently negative, individual charges being less than f40pC. Q values were within the inductive limit for a thundercloud at breakdown but no systematic relation between Q and d was found.Six penetrations were made through the thundercloud of 15 August, which produced only two lightning strokes. The E, records were indicative of a (k) dipole located near the cloud top, at around -13°C. Fields of up to about lOOkVm-' and p,, values (positive and negative) of around 5Ckm-3 were measured. Q values of up to i250pC were recorded, with charges around i~50 pC being commonly found. No systematic Q-drelation was revealed, and smaller precipitation particles frequently carried charges (positive or negative) in excess of the inductive limit. On both days estimated precipitation rates were of order IOmmh-' and on most occasions the pilot reported precipitation particles to be either 'ice' or 'mixed liquid water and ice'.

Field identification of a unique globally dominant mechanism of thunderstorm electrification

“…The charge transfer per collision under the inductive mechanism, and more particularly the maximum charge that a graupel pellet can hold, is proportional to the field-strength E, from which it follows that electric field-growth is very slow until E has grown by two or three orders of magnitude to approach breakdown values. Several field studies (Gaskell et al, 1978;Christian et al, 1980;Dye et al, 1988) have shown that graupel pellets often possess charges which are orders of magnitude more than those that any form of the inductive mechanism could convey to them at that stage of field development. The strong relationship between f and ice crystal mass-flux (Deierling et al, 2005;Deierling 2006) is inconsistent with inductive mechanism (1), as is the observed increase of f with decreasing Tb and increasing IWP observed in the TRMM data analyses.…”

“…Christian et al, 1980;Latham, 1981;Dye et al, 1988;Saunders, 1993;McGorman and Rust, 1998) has led to the generally accepted view that although several charge transfer processes could contribute -sometimes in a significant way -to the development of strong electric fields in thunderstorms, culminating in lightning, the dominant charging mechanism is probably the so-called non-inductive process (e.g. Reynolds et al, 1957;Takahashi, 1978;Jayaratne et al, 1983;Avila et al, 1988;Norville et al, 1991;Saunders et al, 1991;McGorman and Rust, 1998;Saunders and Peck, 1998;Takahashi and Miyawaki, 2002;Mansell et al, 2005).…”

Electric Structure of Oceanic Tropical Clouds and Charge Separation Processes

“…The purpose of this work is to study the charge accumulation process in clouds with respect to cloud top height, in order to identify plausible charge separation processes. Since the precipitation particle charge contributes substantially to the total space charge (radiosonde measurements by Takahashi, 1965Takahashi, , 1978bRust and Moore, 1974;Marshall and Winn, 1982; aircraft measurement by Gunn, 1950;MacCready and Proudfit, 1965;Latham and Stow, 1969;Gaskell et al, 1978;Christian et al, 1980), the electric charge of precipitation particles was measured both at the ground and in the cloud. After the contribution of the measured particle space charge to the total space charge was examined, possible electric charge separation processes for each cloud system were discussed.…”

The Mirror Image Relation in the Vertical Distributions of Electric Field and Precipitation Charge in Winter Thunderclouds

“…In the flight observation by Gaskell et al (1978), both the signs of electric field and charge on precipitation particles were negative in five cases among six flights, namely, the inverse relation was predominant. In the observation of Christian et al (1980), the inverse relation was observed in one case, while positive relation was noted in another case.…”