William H. Beasley

TELEX The Thunderstorm Electrification and Lightning Experiment

Measurements during TELEX by a lightning mapping array, polarimetric and mobile Doppler radars, and balloon-borne electric-field meters and radiosondes show how lightning and other electrical properties depend on storm structure, updrafts, and precipitation formation.

Initial results from simultaneous observation of X-rays and electric fields in a thunderstorm

With an X ray detector designed for flight on a free balloon, we obtained a sounding of X ray intensity and electric-field strength in a mesoscale convective system (MCS) near Norman, Oklahoma, in the spring of 1995. The balloon passed through a region of high electric field strength, at which time an increase in X ray intensity of about 2 orders of magnitude occurred, lasting for approximately 1 min. The X ray intensity returned to background levels at the time of a lightning flash that reduced the electric field strength measured at the balloon. This observation suggests that the production mechanism for the X rays we observed is related to the storm electric field and not necessarily to lightning discharge processes.

Effect of warming and drought on grassland microbial communities

The soil microbiome is responsible for mediating key ecological processes; however, little is known about its sensitivity to climate change. Observed increases in global temperatures and alteration to rainfall patterns, due to anthropogenic release of greenhouse gases, will likely have a strong influence on soil microbial communities and ultimately the ecosystem services they provide. Therefore, it is vital to understand how soil microbial communities will respond to future climate change scenarios. To this end, we surveyed the abundance, diversity and structure of microbial communities over a 2-year period from a long-term in situ warming experiment that experienced a moderate natural drought. We found the warming treatment and soil water budgets strongly influence bacterial population size and diversity. In normal precipitation years, the warming treatment significantly increased microbial population size 40–150% but decreased diversity and significantly changed the composition of the community when compared with the unwarmed controls. However during drought conditions, the warming treatment significantly reduced soil moisture thereby creating unfavorable growth conditions that led to a 50–80% reduction in the microbial population size when compared with the control. Warmed plots also saw an increase in species richness, diversity and evenness; however, community composition was unaffected suggesting that few phylotypes may be active under these stressful conditions. Our results indicate that under warmed conditions, ecosystem water budget regulates the abundance and diversity of microbial populations and that rainfall timing is critical at the onset of drought for sustaining microbial populations.

A Statewide Trial of the SafeCare Home-based Services Model With Parents in Child Protective Services

OBJECTIVES: In this trial, we compared Child Protective Services (CPS) recidivism outcomes between the home-based SafeCare (SC) model for child neglect and comparable home-based services, but without SC modules, for parents in the CPS system across 2 quality control strategies: coached (C) and uncoached implementation. SC is a home-based behavioral skills training model designed for neglecting or maltreating parents. The study was conducted in a scaled-up, statewide implementation setting. METHODS: Two thousand one hundred seventy-five maltreating parents, treated by 219 home visitors, were enrolled and treated in a 2 × 2 (SC versus services as usual × C versus uncoached implementation strategy) randomized cluster experiment. Cases were followed for an average of 6 years for CPS recidivism events. Subpopulation analyses were conducted for parents meeting customary SC inclusion criteria. RESULTS: Consistently significant main effects in favor of SC were found across simple and more complex modeling approaches (hazard ratios = 0.74–0.83). Larger effects were found among the subpopulation meeting customary SC inclusion criteria. C implementation yielded smaller and occasionally significant effects in analyses that included more diverse cases falling outside customary SC inclusion criteria. CONCLUSIONS: Findings support the adoption and use of SC within CPS home-based services systems. C implementation may be especially valuable for cases where the client-model fit is less strong.

X‐ray pulses observed above a mesoscale convective system

During a balloon flight into and above the stratiform region of a mesoscale convective system, we observed three x-ray pulses while the balloon was at an altitude of approximately 15 km MSL (atmospheric pressure of 130 mb). These pulses were one to two orders of magnitude above the background x-ray count rate with peak fluxes between 37 and 270 (cm²-s-sr)−1 and durations of about one second. No significant electric field was measured at the time of these pulses.

Lightning subsequent-stroke electric field peak greater than the first stroke peak and multiple ground terminations

For 46 multiple-stroke flashes in which each stroke ground termination was located using a TV camera network and thunder ranging, 15 flashes (33%) had one or more subsequent return strokes whose initial electric field peak normalized to 100 km was greater than the first-stroke field peak of the flash. In 9 of these 15 flashes the subsequent strokes with field peaks greater than the first stroke followed the same channel as the first stroke; in five flashes the subsequent strokes with the greater peaks followed a different channel to ground; and in one flash the subsequent strokes with the greater peaks occurred both in the first-stroke channel and in a different channel. The interstroke intervals immediately preceding the 13 larger subsequent strokes that followed the first-stroke channel had a geometric mean (GM) duration of 98 ms, 1.7 times greater than the GM of 57 ms for all 199 interstroke intervals (46 flashes) without any selection. Eight of the 13 larger subsequent strokes for which leader durations were measurable had a GM leader duration of 0.55 ms, 3.3 times smaller than the GM of 1.8 ms for 117 subsequent leaders with measurable duration in a previously formed channel of the 46 multiple-stroke flashes. For the six larger subsequent strokes that created a new channel to ground, the preceding interstroke interval had a GM of 130 ms, and the leader duration had a GM of 15 ms. No subsequent stroke with peak field exceeding the first in any category had a preceding interstroke interval less than 35 ms. Analysis of direct current measurements from Switzerland shows that subsequent-stroke currents exhibit many features similar to those of Florida subsequent-stroke electric fields. In 22 Florida single-stroke and multiple-stroke ground flashes the distances between multiple channel terminations in a given flash (33 measurements) ranged from 0.3 km to 7.3 km, with a GM of 1.7 km.

Observed dart leader speed in natural and triggered lightning

From a data base consisting of (1) correlated optical and electric field measurements for 11 natural lightning strokes in Florida, (2) correlated optical and current measurements for 32 artificially initiated (triggered) lightning strokes in New Mexico, and (3) correlated optical and current measurements for 36 triggered lightning strokes in Florida, dart leader speed is examined as a function of the following return stroke initial electric field peak, of the following return stroke current peak, and of the duration of the previous interstroke interval (excluding the duration of continuing current, if present). Return stroke current peaks in both New Mexico and Florida triggered lightning were converted to electric field peaks via the field-current regression equation obtained by Willett et al. (1989), while the electric field peaks in Florida natural lightning were converted to current peaks using the current-field regression equation derived by Rakov et al. (1992), both formulas being based on the same Florida triggered lightning measurements. For each of the three data sets, dart leader speed and the following return stroke field peak or current peak are positively correlated. The relations between leader speed and field or current peak for Florida triggered and Florida natural lightning are similar, possibly indicating a similarity between at least some features of dart leaders and return strokes in natural and in triggered lightning at the same geographic location. On the other hand, leaders in New Mexico triggered lightning are, for the same value of return stroke field or current peak, about twice as fast as those in both triggered and natural lightning in Florida, the difference being likely associated with the relatively short preceding interstroke intervals in New Mexico triggered lightning. For all triggered and natural lightning data taken together, there is a weak but statistically significant tendency for lower leader speed to be associated with a longer previous interstroke interval. However, neither the New Mexico triggered lightning data nor the Florida triggered lightning data, when taken separately, show this tendency.

Gamma‐ray emissions observed in a thunderstorm anvil

Balloon-borne gamma-ray and electric-field-change instruments were launched into a daytime summer thunderstorm to evaluate a new experimental design to test hypotheses for the production of transient luminous events (TLE) (eg. sprites, and blue jets) in the mesosphere. While ascending, the instrument triggered many times on the signals from the electric-field-change instrument, recording the gamma-ray background at those times. A greater than three-fold increase in the gamma-ray flux was observed as the balloon descended through a thunderstorm anvil where a strong electric field was suspected to be present. These observations suggest that gamma-ray production in thunderstorms may not be as uncommon as previously believed.

An Unusual Lightning Flash at Kennedy Space Center

A lightning flash that struck the 150-meter weather tower at Kennedy Space Center was studied by several research groups using varioul techniques. The flash had unusually large peak currents and a stepped leader of relatively short duration. The charged regions neutralized by the three return strokes were located within a horizontal layer between heights of about 6 and 8 kilometers, where environmental temperatures were about –10� to –20�C. The charge source for the first return stroke coincided with a vertical shaft of precipitation inferred to have been graupel or hail. Charge sources for subsequent strokes were near the edge of the detectable precipitation echo. The overall channel length was about 10 kilometers. A Vertically oriented intracloud discharge occurred after the three return strokes.

Luminosity characteristics of dart leaders and return strokes in natural lightning

Streak-camera photographs were obtained in daylight for 23 subsequent strokes in five Florida negative cloud-to-ground flashes. Out of the 23 return-stroke streaked images, only 11 were accompanied by leader streaked images, while all 23 leaders were identified in corresponding electric field records. Thus, 12 subsequent leaders (one of which created a new channel to ground) failed to produce luminosity above the daylight background level. The brightest three dart-leader/return-stroke sequences from two flashes have been examined for relative light intensity as a function of time and height. Dartleader light waveforms appear as sharp pulses with 20-to-80% risetimes of about 0.5–1 μs and widths of 2–6 μs followed by a more or less constant light level (plateau). The plateau continues until it is overridden by the return-stroke light waveform, suggesting that a steady leader current flows through any channel section behind the downward moving leader tip before the return-stroke front has passed that channel section. Return-stroke light pulses near ground have 20-to-80% risetimes of about 1–2 μs and amplitudes a factor of 2 to 3 greater than those of the dart-leader light pulses. As opposed to the return-stroke light pulses that suffer appreciable degradation during the upward propagation of the return-stroke front, the dart-leader light pulses preserve their shape, and the pulse amplitude is either more or less constant or increases as the leader approaches ground. The average electric field intensity across the dart-leader front, whose length is inferred from measured light-pulse risetimes and propagation speed to be of the order of 10 m, should be at least an order of magnitude greater than the average electric field intensity across the return-stroke front, whose length is inferred to be of the order of 100 m.