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Thunderstorms are natural laboratories for studying electrical discharges in air, where the vast temporal, spatial, and energy scales available can spawn surprising phenomena that reveal deficiencies in our understanding of dielectric breakdown. Recent discoveries, such as sprites, jets, terrestrial gamma ray flashes, and fast positive breakdown, highlight the diversity of complex phenomena that thunderstorms can produce, and point to the possibility for electrical breakdown/discharge mechanisms beyond dielectric breakdown theory based mainly on laboratory experiments. Here we present one such confounding discovery, termed fast negative breakdown, that does not fit with our current understanding of dielectric breakdown. Our adaptation of radio astronomy imaging techniques to study extremely transient lightning-associated events confirms that electrical breakdown in thunderstorms can begin with oppositely-directed fast breakdown of negative polarity, similar and in addition to fast positive breakdown expected from conventional dielectric theory and recent observations. The discovery of fast negative breakdown calls for an addendum to the physical description of electrical discharges in air., Recent studies have shown that lightning is initiated by a newly-recognized discharge process called fast positive breakdown. Here, the authors present observational evidence of fast breakdown but of negative polarity, seemingly contrary to current understanding of discharge physics.

Simultaneous data from two interferometers separated by 16 km and synchronized within 100 ns was collected for a thunderstorm near Langmuir Lab on October 23, 2018. Analysis via triangulation follo...

In this paper we report the first close, high-resolution observations of downward-directed terrestrial gamma-ray flashes (TGFs) detected by the large-area Telescope Array cosmic ray observatory, obtained in conjunction with broadband VHF interferometer and fast electric field change measurements of the parent discharge. The results show that the TGFs occur during strong initial breakdown pulses (IBPs) in the first few milliseconds of negative cloud-to-ground and low-altitude intracloud flashes, and that the IBPs are produced by a newly-identified streamer-based discharge process called fast negative breakdown. The observations indicate the relativistic runaway electron avalanches (RREAs) responsible for producing the TGFs are initiated by embedded spark-like transient conducting events (TCEs) within the fast streamer system, and potentially also by individual fast streamers themselves. The TCEs are inferred to be the cause of impulsive sub-pulses that are characteristic features of classic IBP sferics. Additional development of the avalanches would be facilitated by the enhanced electric field ahead of the advancing front of the fast negative breakdown. In addition to showing the nature of IBPs and their enigmatic sub-pulses, the observations also provide a possible explanation for the unsolved question of how the streamer to leader transition occurs during the initial negative breakdown, namely as a result of strong currents flowing in the final stage of successive IBPs, extending backward through both the IBP itself and the negative streamer breakdown preceding the IBP., Comment: Typo fixed and reference added. Manuscript is 36 pages. Supplemental Information is 42 pages. This paper is to be published in the Journal of Geophysical Research: Atmospheres. Online data repository: Open Science Framework DOI: 10.17605/OSF.IO/Z3XDA

VHF radiation sources produced by positive breakdown during lightning discharges are generally considered to be both weak and slowly propagating. However, as VHF lightning mapping systems have become more sensitive, even this weak radiation can be mapped. In addition to being a faint process, positive breakdown often produces bursts of energetic activity. During the bursts, the VHF emission is extremely bright, and the breakdown propagates at much higher speeds. Here we present VHF interferometric and time–of–arrival measurements of such fast positive breakdown events produced during three example flashes. Electric field change measurements show that the fast breakdown process carries positive charge. The extent and velocity of the breakdown is estimated by converting the angular source locations provided by the interferometer into Cartesian coordinates using 3-dimensional lightning mapping observations of the flash as a guide. Fast positive breakdown events are found to extend 100–2400 m into virgin air beyond the tip of the preceding positive leader, at speeds of 0.9–9 ×107 m s−1. The observations expand upon earlier observations of such breakdown [Shao et al., 1995]“ and are similar to recently-reported results that fast positive breakdown is the cause of high-power narrow bipolar events (NBEs) [Rison et al., 2016].

Simple Summary Acting to preserve biodiversity can involve harming individual animals. It has recently been argued that conventional practice has placed too much emphasis on the preservation of collective entities, such as populations and species, at the expense of suffering for individuals. At least some advocates of the ‘Compassionate Conservation’ movement find any deployment of lethal measures in the interests of conservation to be unacceptable. This shifts the balance of priorities too far. While conservationists have a duty to minimise harm, and to use non-lethal measures where feasible, there will be serious implications for conservation if this movement were to be widely influential. Furthermore, the ‘do-no-harm’ maxim the compassionate conservationists advocate does not always promote the welfare of individual animals. Abstract Human activity affecting the welfare of wild vertebrates, widely accepted to be sentient, and therefore deserving of moral concern, is widespread. A variety of motives lead to the killing of individual wild animals. These include to provide food, to protect stock and other human interests, and also for sport. The acceptability of such killing is widely believed to vary with the motive and method. Individual vertebrates are also killed by conservationists. Whether securing conservation goals is an adequate reason for such killing has recently been challenged. Conventional conservation practice has tended to prioritise ecological collectives, such as populations and species, when their interests conflict with those of individuals. Supporters of the ‘Compassionate Conservation’ movement argue both that conservationists have neglected animal welfare when such conflicts arise and that no killing for conservation is justified. We counter that conservationists increasingly seek to adhere to high standards of welfare, and that the extreme position advocated by some supporters of ‘Compassionate Conservation’, rooted in virtue ethics, would, if widely accepted, lead to considerable negative effects for conservation. Conservation practice cannot afford to neglect consequences. Moreover, the do-no-harm maxim does not always lead to better outcomes for animal welfare.

Terrestrial Gamma-ray flashes (TGFs) are bursts of gamma-rays initiated in the Earth’s atmosphere by atmospheric lightning. The Terrestrial Gamma-ray flashes discussed in this work were detected at ground level between 2014 and 2018, by the Telescope Array Surface Detector (TASD), a lightning mapping array installed in 2013, and a broadband interferometer and fast sferics sensor installed in 2018. The TASD is a 700 square kilometer ultra high energy cosmic ray detector in the southwestern desert of Utah, U.S.A. It is composed of 507 (3 square meter) plastic scintillator detectors on a 1.2 km square grid. In 2013, a Lightning Mapping Array (LMA) detector and a Slow antenna (SA) were installed at the TASD site. The LMA is a three-dimensional total lightning location system, comprised of nine stations located within and around the TASD array. The SA records the electric field change in lightning discharges. The TASD has become one of the world leading instruments for detection of TGFs from the ground. The downward Gamma-ray showers observed by the TASD detector were all confined to the first 1-2 ms of intracloud and cloud to ground discharges, spanning an overall duration of several hundreds of microseconds. We hypothesize that the observed TGFs are similar to those detected by satellites, but that the TASD ground-based observations are able to detect both the temporal distribution at the source and the full footprint of the gamma shower on the ground. More importantly, the gamma ray bursts observations suggest that the TGFs were produced by one or two particularly energetic leader steps at the initial breakdown pulse (IBP) stage. To confirm such correspondence, an interferometer (INTF) and a fast antenna were installed a few kilometers east of the TASD detector on July 2018. With these additional lightning detection instruments in concert with the TASD cosmic ray observatory, LMA, and SA, we are able, to present, for the first time, observations of the TGFs clearly associated with the IBPs of downward cloud-to-ground flashes and intracloud flashes. This result sheds new light on the origins of Terrestrial Gamma-ray Flashes.

The Telescope Array Surface Detector (TASD) in western Utah is designed for the measurement of Ultra-High-Energy Cosmic Rays (UHECRs) with characteristically low flux. During its ten years of operation, however, TASD recorded at least 24 bursts of gamma-ray showers, each consisting of two or more TASD events within a single millisecond of lightning activity. After implementation of specialized lightning detectors, the bursts were further correlated with lightning leaders preceding each stroke. We conclude that these bursts are downward Terrestrial Gamma Flashes (TGFs), similar to those observed by satellite. These data constitute the majority of all data on such events recorded from the ground. We are recreating observations using Geant4 simulations to better understand the properties of downward TGFs and the acceptance statistics of TASD. Acceleration mechanisms, for example, are poorly understood. Spectra from models such as Relativistic Runaway Electron Avalanche (RREA) and Fast Negative Breakdown (FNB) are used to generate a detector response to replicate empirical properties, especially the unique waveform timing and footprints seen at TASD. This also helps characterize the TASD acceptance and aperture for TGFs in a manner similar to cosmic ray studies.

Two sprite-producing thunderstorms were observed on 8 and 25 June 2012 in northeastern Colorado by a combination of low-light cameras, a lightning mapping array, polarimetric and Doppler radars, the National Lightning Detection Network, and charge moment change measurements. The 8 June event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h. The majority of sprites occurred during a lull in convective strength, as measured by total flash rate, flash energy, and radar echo volume. Mean flash area spiked multiple times during this period; however, total flash rates still exceeded 60 min(sup 1), and portions of the storm featured a complex anomalous charge structure, with midlevel positive charge near 20degC. The storm produced predominantly positive cloud-to-ground lightning. All sprite-parent flashes occurred on the northeastern flank of the storm, where strong westerly upper level flow was consistent with advection of charged precipitation away from convection, providing a pathway for stratiform lightning. The 25 June event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h. The sprites again occurred during a convective lull, with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area. However, all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud. The results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms.

On the morning of 5 June 2013, two cameras of the SpriteCam network concurrently captured a red sprite with diffuse halo over a mesoscale convective system (MCS) passing the panhandle area of Oklahoma. This sprite was produced by a negative cloud-to-ground (CG) stroke with peak current of −103 kA in a manner different from previous observations in several aspects. First of all, the causative stroke of sprite is located by the National Lightning Detection Network (NLDN) in the trailing stratiform of MCS, instead of the deep convection typically for negative sprites. Second, the sprite-producing stroke was likely the first stroke of a multistroke negative CG flash (with ≥6 CG strokes) whose evolution was mainly confined in the lower part of thunderstorm; although the parent flash of sprite might contain relatively long in-cloud evolution prior to the first stroke, there is no evidence that the negative leader had propagated into the upper positive region of thundercloud as typically observed for the sprite-producing/class negative CG strokes. Third, as shown by the simulation with a two-dimensional full-wave electrodynamic model, although the impulse charge moment change (−190 C km) produced by the main stroke was not sufficient to induce conventional breakdown in the mesosphere, a second impulse charge transfer occurred with ~2 ms delay to cause a substantial charge transfer (−290 C km) so that the overall charge moment change (−480 C km) exceeded the threshold for sprite production; this is a scenario different from the typical case discussed by Li et al. (2012). As for the source of the second current pulse that played a critical role to produce the sprite, it could be an M component whose charge source was at least 9 km horizontally displaced from the main stroke or a negative CG stroke (with weak peak current for the return stroke) that was not detected by the NLDN.

The outcomes of species recovery programs have been mixed; high-profile population recoveries contrast with species-level extinctions. Each conservation intervention has its own challenges, but to inform more effective management it is imperative to assess whether correlates of wider recovery program success or failure can be identified. To contribute to evidence-based improvement of future conservation strategies, we conducted a global quantitative analysis of 48 mammalian recovery programs. We reviewed available scientific literature and conducted semistructured interviews with conservation professionals involved in different recovery programs to investigate ecological, management, and political factors associated with population recoveries or declines. Identifying and removing threats was significantly associated with increasing population trend and decreasing conservation dependence, emphasizing that populations are likely to continue to be compromised in the absence of effective threat mitigation and supporting the need for threat monitoring and adaptive management in response to new and potential threats. Lack of habitat and small population size were cited as limiting factors in 56% and 42% of recovery programs, respectively, and both were statistically associated with increased longer term dependence on conservation intervention, demonstrating the importance of increasing population numbers quickly and restoring and protecting habitat. Poor stakeholder coordination and management were also regularly cited by respondents as key weaknesses in recovery programs, indicating the importance of effective leadership and shared goals and management plans. Project outcomes were not influenced by biological or ecological variables such as body mass or habitat, which suggests that these insights into correlates of conservation success and failure are likely to be generalizable across mammals.

A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown., How lightning is initiated inside storms has been a long-standing and fundamental question. Here, the authors report observations of a previously unrecognized type of discharge, called fast positive breakdown, that is found to initiate many and potentially all lightning discharges in storms.

The upgraded VHF digital interferometer (VHF DITF) system is introduced which can continuously sample the radiation associated with lightning. A new processing technique was implemented which uses the distribution of slopes of the phase difference versus frequency to locate the radiation source. By using this technique, frequency components which are not due to lightning can be excluded and low as well as high amplitude sources are located. As a result, both positive breakdown and negative breakdown are located, and negative recoil leaders (recoil leaders) are visualized in great detail. The recoil leaders which continue into the positive charge region are seen to slow their propagation and dim their radiation as they cross the flash initiation region. Analysis of the relative received power of the different breakdown types, negative leaders, recoil leaders, and positive leaders, also can be made. In both the intracloud and cloud-to-ground flash, the modes of the distributions of received power for negative leaders, recoil leaders, and positive leaders were approximately the same. The brightest emissions seen from the positive leader were substantially lower than the brightest emission seen from the negative leader. The results also indicate that positive leaders as well as lower elevation negative leader emit more low frequency radiation than recoil leaders and high-elevation negative leaders. By continuously sampling the VHF waveform, the upgraded VHF DITF locates many weak sources which the previous system was not capable of locating.

The VHF Broadband Digital Interferometer developed by Osaka University has been improved to allow continuous sampling over the entire duration of a lightning flash and to utilize a generalized cross-correlation technique for determining the lightning source directions. Time series waveforms of 20-80 MHz signals received at three orthogonally located antennas are continuously digitized over multisecond intervals, as opposed to sequences of short-duration triggers. Because of the coherent nature of the measurements, radiation sources are located down into the ambient receiver and environmental noise levels, providing a quantum leap in the ability to study lightning discharge processes. When postprocessed using cross correlation, the measurements provide angular uncertainties less than 1 ! and time resolution better than 1!s. Special techniques have been developed to distinguish between actual lightning sources and noise events, with the result being that on the order of 50,000-80,000 radiation sources are located for a typical lightning flash. In this study, two-dimensional interferometer observations of a classic bilevel intracloud flash are presented and combined with three-dimensional Lightning Mapping Array observations to produce a quasi 3-D map of lightning activity with the time resolution of the interferometer. As an example of the scientific utility of the observations, results are presented for the 3-D progression speed of negative leaders associated with intracloud K-leaders.

[1] The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically 30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from ~10 km MSL (−35°C) to around 6 km MSL (−10°C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing level or at 7.9 km above ground level.

[1] We report and analyze 3 years of lightning impulse charge moment change (iCMC) measurements obtained from an automated, real time lightning charge moment change network (CMCN). The CMCN combines U.S. National Lightning Detection Network (NLDN) lightning event geolocations with extremely low frequency (≲1 kHz) data from two stations to provide iCMC measurements across the entire United States. Almost 14 million lightning events were measured in the 3 year period. We present the statistical distributions of iCMC versus polarity and NLDN-measured peak current, including corrections for the detection efficiency of the CMCN versus peak current. We find a broad distribution of iCMC for a given peak current, implying that these parameters are at best only weakly correlated. Curiously, the mean iCMC does not monotonically increase with peak current, and in fact, drops for positive CG strokes above +150 kA. For all positive strokes, there is a boundary near 20 C km that separates seemingly distinct populations of high and low iCMC strokes. We also explore the geographic distribution of high iCMC lightning strokes. High iCMC positive strokes occur predominantly in the northern midwest portion of the U.S., with a secondary peak over the gulf stream region just off the U.S. east coast. High iCMC negative strokes are also clustered in the midwest, although somewhat south of most of the high iCMC positive strokes. This is a region far from the locations of maximum occurrence of high peak current negative strokes. Based on assumed iCMC thresholds for sprite production, we estimate that approximately 35,000 positive polarity and 350 negative polarity sprites occur per year over the U.S. land and near-coastal areas. Among other applications, this network is useful for the nowcasting of sprite-producing storms and storm regions.

Despite a wide distribution through Africa, the genus Alcelaphus has been little studied. The aim of the work described here was the study of a population of Coke's hartebeest in the Athi Plains of Kenya, which included the Nairobi National Park. It was designed to complement existing information on the species' behaviour and to examine the interactions between the hartebeest and their food supply. The approach, both in the field and subsequently, is also described in Ch.1. In Ch.2 I describe the methods which are referred to frequently through later chapters. These include the field methods of counting and ageing hartebeest, the location of study areas and the sampling of vegetation, the measurement of rainfall and the collection of specimen animals. The organisation of the resulting data and their analysis are described. Descriptions of the Athi Plains are few. Their geology and topography are outlined in Ch.3, while Ch.4 concerns their climate, with the emphasis on rainfall as the most important seasonal parameter. The vegetation of the Nairobi Park and the rest of the plains is then described (Ch.6) at the level of the vegetation zones for the whole plains (1850 km2) and of vegetation types for the study areas. The Nairobi Park is shown to have a very varied vegetation despite its small size (114 km2). In Ch.6 the sizes and distributions of the populations of hartebeest and other numerous herbivores are described from aerial censuses over the plains and ground counts in the park. This establishes that the density of hartebeest in the park is 6.6 times that of the plains. The latter population also contains significantly fewer adult females and young above the age of 1 month. The hartebeest in the plains show very minor population movements compared to either wildebeest or zebra, and exchange with the park population is infrequent. Using information theory methods, Ch.7 serves to define the niche of the hartebeest in relation to those of other herbivore species, and to compare the structure of the communities of the two areas. The herbivore community of the plains also includes cattle, sheep and goats. The results of this ground-work confirm the sedentary existence of the hartebeest population, but show it to occupy a relatively wide variety of vegetation zones through the year, occupying many vegetation types and tolerating a broad range of grass standing crops. Compared to other species, the hartebeest shows a very marked seasonal occupation of vegetation types in the park, but this is not apparent in the plains. The same methods are extended to measure the similarity between species' distributions, and the cases of high overlaps are examined using published information on the feeding habits and diets of the species. Considerable ecological separation can be inferred between all species- pairs except between hartebeest and zebra in the park in the dry season, and between hartebeest and cattle in the plains in the wet season. The distributions of the latter pair in the dry season, also, suggest their ecological equivalence. In Ch.8, starting Part II, I describe the hartebeest's diet and its seasonal changes from the analysis of rumen contents. The hartebeest grazes exclusively. Its diet is described in terms of its content of grass parts, rather than grass species, amongst which Themeda triandra is shown by various sources to be predominant. The effects of the differential digestion of these parts in the rumen are reversed by applying a correction factor based on specific gravity (Appendix 12) to obtain the diet proportions. In the wet season the proportion of leaf in the diet is higher than in the sward, while the less nutritious stem is under-represented. When the leaf in the sward has been depleted in the dry season, the hartebeest no longer exercise any dietary selection. Comparison of these results with those published for zebra show that the parts taken by the 2 species are very different in proportion, and I conclude that this would result in their ecological separation even when feeding together. On the other hand, comtemporary evidence on cattle diets, also from the Athi Plains, shows them to be taking the same diet as the hartebeest, and evidence is presented that Themeda is also frequently eaten by cattle. Their coincident distributions are parallelled by similarities in their rumen morphology and bacteriology, with both classified as the only "bulk roughage grazers" in the Athi Plains community. The method developed for the correction of grass part proportions in the rumen to those in the diet allows the daily dry matter intake to be calculated from the weight of dry matter in the rumen (Ch.9). Intake varied between 26 and 87 g/kg.W.73.day in the dry and wet seasons respectively, through the effect of the water content of the food on its specific gravity and subsequent behaviour in the rumen. The calculated variation in intake with the succulence and quality of the food is consistent with experimental observations on the factors controlling the intake of coarse feeds by domestic ruminants. The calculated intakes are similar to those of 42 and 34 g/kg.W.73.day of an experimental hartebeest and sheep, respectively. A regression method for predicting the hartebeest's intake under field conditions from the faecal nitrogen content is developed. In Ch.10 the dry matter intake is converted into the intakes of protein and energy, and the gain to the hartebeest of selective feeding is calculated. Selection appears capable of increasing the digestible crude protein intake by 50%. The calculated intakes are compared with maintenance standards for domestic ruminants and are shown to have fallen below the maintenance levels in the dry season of September 1972. Calculation of the intakes uses information from a feeding trial with hartebeest and sheep, whose intakes were also measured. The experimental hartebeest's metabolisable energy intake was 51.5 kcal/kg.W.73.day, which was considerably lower than the measured metabolic heat production of 116.1 kcal/kg.W.73.day of another tame animal. The metabolisable energy intake of the sheep of 45.1 kcal/kg.W.73.day suggests that the lower metabolic rate may be more correct, and further supporting evidence is presented. Chapter 11 is the first of 3 chapters in which the hartebeest's energy expenditure is considered. The daily activity patterns are described from day and night observations in the wet and dry seasons. Little seasonal variation in the regime of 3 feeding periods at nearly equal intervals through 24 hours was apparent. The total times spent feeding was 2 hours shorter at 8.6 h/24h in the dry season than the wet. About half of this reduction was made up by an increase in the time spent walking, associated with the need to visit water sources in the dry season. Further observations showed that males drank every 3 days, females every 2 days. The energy cost of this activity was almost the same in both seasons at 52% greater than the basal metabolic energy expenditure. The use of energy for growth and the deposition of body reserves is considered in Ch.12. The shot animals showed that full adult body weight is not reached until the fourth year, after which weight appears to decline immediately. Using a photographic method the external condition of territorial males was shown to depend on the rainfall over the previous 4 months. Non-territorial males were always in significantly better condition. The shot hartebeest were characterised by very small kidney fat reserves which showed no seasonal variation. Marrow fat varied seasonally, as did the weight of a selected muscle, representing the protein reserves of the body. The latter also changed through age, parallelling the changes in total body weight. The significance of these findings is discussed in the light of the low fat content of tropical ungulates, the hartebeest's slow growth rate and its possible adaptiveness. The small surpluses of energy ingested by the hartebeest and the small body reserves lead to a discussion of the female reproductive pattern (Ch.13). First breeding occurs in the fourth year. Calving occurs in every month of the year. The timing and size of the birth peaks allow the conclusion that nutrition and female condition are the ultimate and proximate factors influencing reproduction. The adaptiveness of this system to a fluctuating, equatorial environment is discussed. In Ch.14 the utilization of the resources of food and water of the park are considered. The hartebeest's seasonal use of the vegetation, mentioned in Ch.7, is described, and is shown to be clearly defined and predictable. The data necessary for a causal analysis of the grazing cycle were not available. The quantity of standing water in the park study area is shown to depend on the rainfall over the previous 2 months. Only under exceptional conditions does animal use make significant inroads in to the water resources. Comparing this study area with those in the plains, the abundance of water in the park is due to the construction of dams rather than to any greater water-retaining capacity. In the dry season, the hartebeest aggregate around the remaining water sources. This provides evidence additional to that in Ch.11 that the hartebeest conserve energy by reducing their activity when experiencing sub-maintenance intakes in the dry season. The significance of this to the distribution of the hartebeest in the plains is discussed. In the final discussion (Ch.15) the ecology of the hartebeest is compared with those of several other species. Most notably, the hartebeest differs from the related wildebeest by being more sedentary, eating a poorer quality diet, growing more slowly, reaching sexual maturity later, but calving as often as conditions allow, followed by a high calf survival rate. In their "opportunistic" reproduction and prolonged mother-offspring bond, the hartebeest resemble some of the desert marsupials. The relationship between cattle and hartebeest is considered in more depth. Their ecological equivalence (Chs.7,8) is shown to lead to their competition both through exclusion on the part of the cattle, and exploitation for the same food. The hartebeest is the competitively inferior species, and their density and lower proportion of young animals in the plains are identified as the results of this interaction. Archaeological and historical evidence confirms that similar habitat selection by Bos spp. and Alcelaphus spp. has occurred over a long time throughout the African continent. Finally, the reasons for the predominance of the hartebeest in the park since 1961 is discussed, and it is concluded that the high densities observed in 1971-72 were not unusual in historical times. The management practice of burning the park's vegetation has allowed further increases in numbers, while the large numbers of cattle in the plains have caused the reverse.

This paper is a personal view, deriving from the knowledge base of the Arabian Peninsula’s fauna, the record on re-introduction of Arabian Oryx and Houbara Bustard, and selective conservation actions for the region’s species, to propose an ambitious vision for restoring the region’s key ecosystems through re-wilding, a holistic approach for biodiversity conservation. It is argued that the need is urgent and the time is right, and that various circumstances and opportunities are now favourable. The prospect is for the Arabian Peninsula to maintain its roles as home to specialised species, to continue to act as a sanctuary and crossroads for species from three major neighbouring biological realms, and to be a potential refuge in the face of climate change.

Blue jets, gigantic jets, cloud-to-cloud discharges and cloud-to-ground lightning are all electrical discharges from thunderclouds. An analysis of numerical simulations and observations of these phenomena places them all in a unifying framework. Thunderstorms occasionally produce upward discharges, called blue jets and gigantic jets, that propagate out of the storm top towards or up to the ionosphere1,2,3,4. Whereas the various types of intracloud and cloud-to-ground lightning are reasonably well understood, the cause and nature of upward discharges remains a mystery. Here, we present a combination of observational and modelling results that indicate two principal ways in which upward discharges can be produced. The modelling indicates that blue jets occur as a result of electrical breakdown between the upper storm charge and the screening charge attracted to the cloud top; they are predicted to occur 5–10 s or less after a cloud-to-ground or intracloud discharge produces a sudden charge imbalance in the storm. An observation is presented of an upward discharge that supports this basic mechanism. In contrast, we find that gigantic jets begin as a normal intracloud discharge between dominant mid-level charge and a screening-depleted upper-level charge, that continues to propagate out of the top of the storm. Observational support for this mechanism comes from similarity with ‘bolt-from-the-blue’ discharges5 and from data on the polarity of gigantic jets6. We conclude that upward discharges are analogous to cloud-to-ground lightning. Our explanation provides a unifying view of how lightning escapes from a thundercloud.

The Milu (Père David’s deer, Elaphurus davidianus) became extinct in China in the early 20th century but was reintroduced to the country. The reintroduced Milu escaped from a nature reserve and dispersed to the south of the Yangtze River. We monitored these accidentally escaped Milu from 1995 to 2012. The escaped Milu searched for vacant habitat patches as “stepping stones” and established refuge populations. We recorded 122 dispersal events of the escaped Milu. Most dispersal events occurred in 1998, 2003, 2006 and 2010. Milu normally disperse in March, July and November. Average dispersal distance was 14.08 ± 9.03 km, with 91.41% shorter than 25 km. After 5 generations, by the end of 2012, 300 wild Milu were scattered in refuge populations in the eastern and southern edges of the Dongting Lake. We suggest that population density is the ultimate cause for Milu dispersal, whereas floods and human disturbance are proximate causes. The case of the Milu shows that accidentally escaped animals can establish viable populations; however, the dispersed animals were subject to chance in finding “stepping stones”. The re-wilded Milu persist as a meta-population with sub-populations linked by dispersals through marginal habitats in an anthropogenic landscape.

Since 1998, Los Alamos National Laboratory (LANL) has deployed an array of fast electric field change sensors in New Mexico and Florida in support of LANL’s satellite lightning observations. In April 2004, all the sensors were significantly upgraded and improved, and a new array was deployed in north-central Florida. This paper describes the operations of the new array and reports the first 12 months of lightning observations. The new array is about 10 times more sensitive than the previous one and can capture millions of discharge events during a stormy day in Florida. In this paper, the array’s lightning location accuracy, minimum detectable peak current, and ratio of intracloud-to-cloud-to-ground flashes are analyzed. Some case studies that illustrate the storm evolution, lightning classification, and radar comparisons are presented. A new three-dimensional capability of the array is demonstrated.

The lightning data that are recorded with a three-dimensional lightning mapping array (LMA) are compared with data from an electric field change sensor (in this case a flat-plate antenna operated both as a “slow” and a “fast” antenna). The goal of these comparisons is to quantify any time difference that may exist between the initial responses of the two instruments to a lightning flash. The data consist of 136 flashes from two New Mexico thunderstorms. It is found that the initial radiation source detected by the LMA usually precedes the initial response of both the slow and fast antennas. In a small number of cases, the flat-plate antenna response precedes the initial LMA source, but by no more than 2 ms. The observations of such a close time coincidence suggest that the first LMA radiation source of each flash was located at or very near the flash-initiation point. Thus, the first LMA radiation source and the initial sequence of sources from a lightning flash can be used as remote sensing tools to give information about the magnitude of the electric field (relative to lightning-initiation thresholds) and the direction of the electric field at the initiation location.

The aim of this study was to review MRI findings of clinically suspected posterolateral corner knee injuries and their associated internal derangements. Sixteen knees in 15 patients who had evidence of a posterolateral corner knee injury on the physical exam underwent MRI to evaluate the posterolateral corner of the knee and to look for associated injuries. Two musculoskeletal radiologists reviewed the scans. Surgery was performed on 10 of the knees. Tibial plateau fractures were present in 6 knees; 5 of the fractures were anteromedial rim tibial plateau fractures. The popliteus muscle was injured in 13 knees and the biceps femoris in 6 knees. The lateral collateral ligament was ruptured in 12 knees. The posterior cruciate ligament was completely ruptured in 7 knees and avulsed from its tibial attachment in 1 knee. Eleven knees had a complete anterior cruciate ligament rupture. The anterior cruciate ligament was edematous without complete disruption of all fibers in 3 knees. There was excellent correlation between the MRI results and operative results in regard to the presence of a posterolateral corner injury of the knee (9 of the 10 knees had a posterolateral corner injury). In our study MRI readily detected posterolateral corner injuries. Posterolateral corner injuries of the knee are frequently associated with a variety of significant injuries, including cruciate ligament tears, meniscus tears, and fractures. Fractures of the peripheral anteromedial tibial plateau are not common; however, given their relatively common occurrence in this study, they may be an indicator of a posterolateral corner injury to the knee.

During the summer of 2000, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) program deployed a three-dimensional Lightning Mapping Array (LMA) near Goodland, Kansas. Video confirmation of sprites triggered by lightning within storms traversing the LMA domain were coordinated with extremely low frequency (ELF) transient measurements in Rhode Island and North Carolina. Two techniques of estimating changes in vertical charge moment (Mq) yielded averages of ;800 and ;950 C km for 13 sprite-parent positive polarity cloud-to-ground strokes (1CGs). Analyses of the LMA’s very high frequency (VHF) lightning emissions within the two mesoscale convective systems (MCSs) show that 1CGs did not produce sprites until the centroid of the maximum density of lightning radiation emissions dropped from the upper part of the storm (7‐11.5 km AGL) to much lower altitudes (2‐5 km AGL). The average height of charge removal (Zq) from 15 sprite-parent 1CGs during the late mature phase of one MCS was 4.1 km AGL. Thus, the total charges lowered by spriteparent 1CGs were on the order of 200 C. The regional 08C isotherm was located at about 4.0 km AGL. This suggests a possible linkage between sprite-parent CGs and melting-layer/brightband charge production mechanisms in MCS stratiform precipitation regions. These cases are supportive of the conceptual MCS spriteproduction models previously proposed by two of the authors (Lyons and Williams).

A variety of storm top electrical discharges have been observed using several types of low-light imagers, film, and the human eye. Recently, a video recorded an unprecedented, bright blue upward discharge from a tropical thunderstorm top near Puerto Rico. The event reached the base of the ionosphere. The horizontal dimensions of cloud top discharges can range from 100 m to several kilometers. Upward extents vary from 100 m to 70 km. Shapes include “points” of light, upwardly flaring trumpets, and narrow, vertical, lightning-like channels, some topped with expanding blue, flame-like features. Visual appearances range from brilliant white lightning-like channels to a grainy, almost particulate appearing jets of dim blue light, and sometimes as a blue flame within which a brilliant white channel appears. The classical blue jet is at the lower limit of human night vision whereas some upward discharges have been clearly seen during daylight. Cloud top “pixies” last no longer than 16.7 ms, whereas upward lightn...

The outcomes of species recovery programs have been mixed; high-profile population recoveries contrast with species-level extinctions. Each conservation intervention has its own challenges, but to inform more effective management it is imperative to assess whether correlates of wider recovery program success or failure can be identified. To contribute to evidence-based improvement of future conservation strategies, we conducted a global quantitative analysis of 48 mammalian recovery programs. We reviewed available scientific literature and conducted semistructured interviews with conservation professionals involved in different recovery programs to investigate ecological, management, and political factors associated with population recoveries or declines. Identifying and removing threats was significantly associated with increasing population trend and decreasing conservation dependence, emphasizing that populations are likely to continue to be compromised in the absence of effective threat mitigation and supporting the need for threat monitoring and adaptive management in response to new and potential threats. Lack of habitat and small population size were cited as limiting factors in 56% and 42% of recovery programs, respectively, and both were statistically associated with increased longer term dependence on conservation intervention, demonstrating the importance of increasing population numbers quickly and restoring and protecting habitat. Poor stakeholder coordination and management were also regularly cited by respondents as key weaknesses in recovery programs, indicating the importance of effective leadership and shared goals and management plans. Project outcomes were not influenced by biological or ecological variables such as body mass or habitat, which suggests that these insights into correlates of conservation success and failure are likely to be generalizable across mammals.

In dryland ecosystems, mobility is essential for both wildlife and people to access unpredictable and spatially heterogeneous resources, particularly in the face of climate change. Fences can prevent connectivity vital for this mobility. There are recent calls for large-scale barrier fencing interventions to address human-wildlife conflict and illegal resource extraction. Fencing has costs and benefits to people and wildlife. However, the evidence available for facilitating sound decision-making for fencing initiatives is limited, particularly for drylands. We identify six research areas that are key to informing evaluations of fencing initiatives: economics, edge permeability, reserve design, connectivity, ecosystem services and communities. Policy implications. Implementing this research agenda to evaluate fencing interventions in dryland ecosystems will enable better management and policy decisions. The United Nations Conventions on Migratory Species (CMS) and to Combat Desertification (UNCCD) are appropriate international agreements for moving this agenda forward and leading the development of policies and guidelines on fencing in drylands. Implementing this research agenda to evaluate fencing interventions in dryland ecosystems will enable better management and policy decisions. The United Nations Conventions on Migratory Species (CMS) and to Combat Desertification (UNCCD) are appropriate international agreements for moving this agenda forward and leading the development of policies and guidelines on fencing in drylands.

A digital broadband interferometer (INTF), based on a system developed at Osaka University [1], but with an upgraded streaming digitizer system, has been deployed at Langmuir Laboratory for the past four summers. The upgraded system allows lightning to be located continuously in time over a broad range of source powers. The data are processed using a cross correlation based algorithm and further enhanced using maximum likelihood windowing functions. The resulting 2D images are highly detailed, having sub-microsecond time resolution as well as good angular resolution that allow the development of positive and negative leaders to be examined in detail. Continuously radiating events such as K-changes and dart leaders are imaged in their entirety, and impulsive events associated with stepping can be isolated in time. The continuous INTF is a highly complementary instrument to the New Mexico Tech Mapping Array (LMA). The LMA locates impulsive VHF radiation events accurately in 3D with up to 10 microsecond time resolution, while the INTF locates both continuous and impulsive radiating events with sub-microsecond resolution in 2D. The combined datasets provide more complete observations and understanding of lightning processes than obtained by either system alone. Ambiguities in the interferometer data arising from sources moving towards or away from the interferometer are removed. The timing resolution of the LMA is improved to that of the interferometer. Continuously radiating emissions such as K-changes and dart leaders can be mapped in 3D. The combined continuous INTF and LMA system is proving to be a very powerful tool for the study of lightning electrical breakdown processes. A number of previously unobserved phenomena have been discovered using the INTF. Of significant importance is the observation of fast (5 × 107 m/s) positive breakdown which radiates strongly in the VHF. Fast positive streamers, about 500 m long, are often observed as the first event in a lightning flash, and may be the mechanism which initiates lightning. Fast positive breakdown, typically several kilometers long, is also observed following return strokes of negative CG ashes, propagating into regions of previously un-ionized air.

Summary Coiled-tubing drilling (CTD) has thrived in recent years on the North Slope of Alaska. To date, CTD has sidetracked more than 250 wells in a continuous program of activity since 1995. In that time, Alaska has become a proving ground for CTD tools and techniques. CTD has matured into a highly efficient and economical means of sidetracking wells on the North Slope. Key reasons for the success of the program include continuous use, which allows rapid learning; a culture of technical innovation; effective performance-based service contracts; the right people with the right expertise; and the vision and support of senior management. This paper summarizes the performance improvements realized in North Slope CTD operations, detailing how the tools and techniques have changed. Applying new technologies and improving existing tools are major levers of CTD progress. Major performance improvement areas include window milling, bottomhole assembly (BHA) reliability, and lost circulation. Reliability improvements in equipment and persistent innovation will continue to fuel CTD's underlying economic performance in Alaska. Included in this paper is a discussion of the remaining problems associated with through-tubing, slim-hole drilling with CTD technology. Examples of new CTD technologies being used or about to be implemented in Alaska will also be presented.

Confusion in the interpretation of standard-speed video observations of optical flashes above intense cloud-to-ground lightning discharges has persisted for a number of years. New high-speed (3000 frames per second) image-intensified video recordings are used along with theoretical modeling to elucidate the optical signatures of elves and sprites. In particular, a brief diffuse flash sometimes observed to accompany or precede more structured sprites in standard-speed video is shown to be a normal component of sprite electrical breakdown and to be due entirely to the quasi-electrostatic thundercloud field (sprites), rather than the lightning electromagnetic pulse (elves). These “sprite halos” are expected to be produced by large charge moment changes occurring over relatively short timescales (∼1 ms), in accordance with their altitude extent of ∼70 to 85 km. The relatively short duration of this upper, diffuse component of sprites makes it difficult to detect and to discriminate from elves and Rayleigh-scattered light using normal-speed video systems. Modeled photometric array signatures of elves and sprites are contrasted and shown to be consistent with observations. Ionization in the diffuse portion of sprites may be a cause of VLF scattering phenomena known as early/fast VLF events.

On August 14, 1998, 3 separate daytime sprite events were detected via a unique extremely low frequency (ELF) sprite signature. The onset of the sprite ELF signatures was delayed by 11.0–13.2 ms from positive cloud-to-ground strokes which had attained exceptionally large charge moment (charge times height) changes of 3900–6100 C·km. It is shown that a charge moment change of 6100 C·km may have been sufficient for conventional breakdown at ≃54 km altitude, assuming an experimentally measured ion conductivity profile of Holzworth et al., [1985]. The daytime sprites themselves contained unusually large charge moment changes of ≃2800 C·km, ≃1200 C·km, and ≃910 C·km.

High altitude air breakdown, manifested as “red sprites,” is reported in close association with negative cloud-to-ground lightning (−CG) on at least two occasions above an unusual storm on August 29, 1998. Data from high speed photometry, low-light-level video, and receivers of lightning electromagnetic signatures in the frequency range 10 Hz to 20 kHz are used to establish the association and indicate that the causative −CG discharges effected unusually large vertical charge moment changes (ΔMQv) of up to 1550 C · km in 5 ms. The existence of sprites caused by −CG's, rather than the regularly associated +CG's, has immediate implications for sprite models and observations.