Meteorological aspects of winter upward lightning from an instrumented tower in the Pyrenees

A case study of winter upward lightning is analysed. In particular, the study focuses on the meteorological aspects that favoured the triggering of upward lightning by an instrumented tower in the eastern Pyrenees. Starting from the lightning currents measured at the Eagle Nest Tower, and taking advantage of other singular meteorological instruments deployed in the region, the obtained results showed how a small winter thunderstorm can create the necessary conditions for the inception of self-initiated upward lightning from a small tower. Beyond the particularities of the present case study, the results provide new evidence on the necessity to include upward flashes in risk assessment. © 2018 IEEE.Peer ReviewedPostprint (published version

Evolution of gigantic jets at high temporal and spatial resolution

Gigantic Jets (GJ) are lightning discharges between the cloud and the lower ionosphere, which manifest as leaders at low altitude and transition to streamers as they rise in altitude. The evolution has never been imaged before at rates faster than 1/60th second. We ran a campaign in northern Colombia with an intensified high-speed camera at 900 images per second to study the development. The image sequence reveals a weakly luminous stepwise upward propagation from the cloud top to 40 km altitude, after which continuous and much brighter branches grow to the ionosphere in 2 ms. We show the stepping to be consistent with pilot system propagation in streamers.Postprint (author's final draft

Automated analysis and statistics of lightning leader speed, local flash rates and electric charge structure in thunderstorms

We introduce new methods for the analysis of complex three-dimensional lightning data produced by Lightning Mapping Arrays and illustrate them by cases of a mid-latitude severe weather producing thunderstorm and a tropical thunderstorm in Colombia. The method is based on the characteristics of bidrectional leader development as observed in LMA data (van der Velde and Montanyà, 2013), where mapped positive leaders were found to propagate at characteristic speeds around 2 · 10^4 m s-1, while negative leaders typically propagate at speeds around 10^5 m s-1. We fit slopes (t-x, t-y, t-z) to approximate leader speed, which can be used to determine the polarity, and summarize flash rate and polarity characteristics in a 3D grid over time. The summarized data can be used to follow charge structure evolution over time, as well as climatological studies comparing lightning parameters with the meteorological environment of storms.Postprint (author's final draft

Measuring low-current discharges from grounded rods under high background electric fields

This work presents the development of an inductive current sensor for measuring pulsating corona discharges observed under high background electric field. Laboratory and field experiments in different setups are used to corroborate the discharge features. The first location is on the roof of a regular building, and the second is on a flat area. Due to the enhancement of the E-field caused by lightning strikes in the vicinity of a grounded rod with a sharp tip, positive and negative pulses before or after the strikes are observed. When lightning activity is far from the structure, but the electric field remains high, pulses are also observed. Finally, one prototype of this sensor was modified to work as a pulse detector with a higher current threshold, allowing detections of leader currents above 0.5 A. The sensor performance is validated in the laboratory and investigated in the field, in association with lightning events.Peer ReviewedPostprint (published version

Meteorological factors in the production of gigantic jets by tropical thunderstorms in Colombia

Gigantic jets are electric discharges that on rare occasions can be seen at night shooting out of the top of tropical thunderclouds, reaching the ionosphere (90 km). Using sensitive camera systems and detection software, we recorded 70 events over northern Colombia and adjacent seas, most of them captured between 2016 and 2022. This is the first study to compare the meteorological background conditions for thunderstorms that produced gigantic jets in 48 nights against 83 reference cases with monitored thunderstorms that did not produce jets, using vertical profiles from ERA5 reanalysis near the event location. From the vertical profiles, various meteorological parameters are calculated, grouped by metrics of the low level convective parcel, instability, humidity, warm cloud and mixed phase parameters, and vertical wind shear, not limited to default levels. We report statistically significant differences and effect sizes (Cohen's d) for gigantic jet producing environments compared to null environments. Gigantic jets are produced in conditions with reduced low level temperatures in combination with warmer mid levels. This causes a lower cloud base and higher -10 °C isotherm altitude, thus a greater warm cloud depth, as well as reduced updraft and downdraft buoyancy. Over northern Colombia the non-GJ producing storms tend to grow in an environment that supports more vigorous, multicellular convection by enhanced low-level storm-relative winds and stronger downdrafts. Over western Colombia, the non-GJ cases tend to have a lower equilibrium level while having favorable warm cloud parameters. No evidence is found for hypotheses that upper level vertical wind shear enables gigantic jet production, nor are overshooting tops larger. The findings can be used for forecasting gigantic jets and their climatologically optimal regions on Earth. We speculate that the environmental conditions shift the droplet size distribution towards larger drops at the cost of cloud droplets, with enhanced droplet shattering ice multiplication processes as they freeze. Depending on convective evolution, low rime accretion rates could briefly expand the negative charge region downward by inverse polarity charging while the upper positive charge concentration may weaken at the same time, which could lead to a temporary negatively imbalanced electric potential distribution in the cloud needed for gigantic jet emission.Peer ReviewedPostprint (published version

Experiments with a tethered drone to investigate induced charges on a vertically arranged conductor during fair weather

To better understand the phenomena associated with electrostatic charges and potential distribution over vertical conductors, this work describes preliminary results obtained with a tethered drone that is used to lay vertically a 100-m long-stranded copper wire. Several flights were conducted in fair weather conditions. In the first configuration, a conductive spherical shell with a spool for the wire is placed in a Teflon holder and used for ensuring that the charges inducted on the conductive body do not produce any corona from the bottom of the system. A field mill is placed below the sphere at a fixed distance, and its measurement can be used as a reference to the charge distribution over the sphere during the flights. The second configuration consists of grounding the bottom sphere, taking the null potential up to the tip of the wire that is deployed. In this setup, several approaches for measuring currents were explored.Peer ReviewedPostprint (published version

Role of blood glucose in cytokine gene expression in early syngeneic islet transplantation

In islet transplantation, local production of cytokines at the grafted site may contribute to the initial nonspecific inflammation response. We have determined whether the metabolic condition of the recipient modulates the cytokine expression in islet grafts in the initial days after transplantation. Normoglycemic and hyperglycemic streptozotocin-diabetic Lewis rats were transplanted with 500 syngeneic islets, an insufficient beta cell mass to restore normoglycemia in hyperglycemic recipients. The expression of IL-1beta, TNF-alpha, IFN-gamma, IL-6, IL-10, and IL-4 genes was determined by real-time PCR in freshly isolated islets, in 24-h cultured islets and in islet grafts on days 1, 3, and 7 after transplantation. IL-1beta mRNA was strongly and similarly increased in normoglycemic and hyperglycemic groups on days 1, 3, and 7 after transplantation compared with freshly isolated and cultured islets. TNF-alpha mRNA was also strongly increased on day 1, and it remained increased on days 3 and 7. IL-6 and IL-10 were not detected in freshly isolated islets, but their expression was clearly enhanced in 24-h cultured islets and islet grafts. IL-6 was further increased in hyperglycemic grafts. IL-10 expression was increased in both normoglycemic and hyperglycemic grafts on day 1 after transplantation, and remained increased in hyperglycemic grafts compared to 24-h cultured islets. IFN-gamma mRNA was barely detected in a few grafts, and IL-4 mRNA was never detected. Thus, the inflammatory response in islet grafts was maximal on day 1 after transplantation, it was sustained, although at lower levels, on days 3 and 7, and it was partly enhanced by hyperglycemia

Gigantic jet discharges evolve stepwise through the middle atmosphere

In 2002 it was discovered that a lightning discharge can rise out of the top of tropical thunderstorms and branch out spectacularly to the base of the ionosphere at 90¿km altitude. Several dozens of such gigantic jets have been recorded or photographed since, but eluded capture by high-speed video cameras. Here we report on 4 gigantic jets recorded in Colombia at a temporal resolution of 200 µs to 1¿ms. During the rising stage, one or more luminous steps are revealed at 32-40¿km, before a continuous final jump of negative streamers to the ionosphere, starting in a bidirectional (bipolar) fashion. The subsequent trailing jet extends upward from the jump onset, with a current density well below that of lightning leaders. Magnetic field signals tracking the charge transfer and optical Geostationary Lightning Mapper data are now matched unambiguously to the precisely timed final jump process in a gigantic jet.Peer ReviewedPostprint (published version

Limited Joint Mobility Progression In Type 1 Diabetes: A 15-year Follow-up Study

Objective. To assess the evolution of joint mobility over a period of 15 years in type 1 diabetic patients and healthy controls and to determine whether microalbuminuria is associated with a different evolution of joint mobility. Methods. Joint mobility of hand and wrist was determined in 63 patients with type 1 diabetes and 63 healthy subjects. Fifteen years later, 37 (58.7%) diabetic patients and 16 (25.4%) healthy subjects were studied again. Joint mobility was assessed with the Prayer sign and by measuring the angle of maximal flexion of the fifth and third metacarpophalangeal (MCP) joints and wrist. Patients with diabetes were visited 2-4 times every year with regular assessment of glycated hemoglobin (HbA1(c)), urinary albumin excretion (UAE), and ophthalmoscopy. Results. Fifteen years after the initial exam, diabetic patients showed reduced flexion of the fifth MCP joint (82.6 +/- 5.8 versus 76.0 +/- 6.4 degrees, p < 0 001) and wrist (75.9 +/- 8.1 versus 73.2 +/- 7.4 degrees, p = 0 015) compared to baseline examination. Joint mobility did not change significantly in healthy subjects. Patients with microalbuminuria showed greater reduction in hand joint mobility than diabetic patients with normal UAE or than healthy subjects (p < 0 001). Conclusions. In type 1 diabetic patients, the severity of LJM progresses with time, and the progression is enhanced in patients with microalbuminuria

Short term culture with the caspases inhibitor z-VAD fmk reduces beta cell apoptosis in transplanted islets and improves the metabolic outcome of the graft

In the initial days after transplantation islets are particularly vulnerable and show increased apoptosis and necrosis. We have studied the effects of caspase inhibition on this early beta cell death in syngeneically transplanted islets. Streptozotocin-diabetic C57BL/6 mice were transplanted with 150 syngeneic islets, an insufficient mass to restore normoglycemia, preincubated with or without the pan-caspase inhibitor z-VAD. fmk 2 h before transplantation. Beta cell apoptosis was increased in control islets on day 3 after transplantation (0.28 ± 0.02%) compared with freshly isolated islets (0.08 ± 0.02%, p< 0.001), and was partially reduced in transplanted islets preincubated with z-VAD.fmk 200 μM (0.14 ± 0.02%, p = 0.003) or with z-VAD.fmk 500 μM (0.17 ± 0.01%, p = 0.012), but not with a lower z-VAD.fmk (100 μM) concentration. Diabetic mice transplanted with islets preincubated with z-VAD.fmk 500 μM showed an improved metabolic evolution compared with control and z-VAD.fmk 200 μM groups. The z-VAD.fmk 500 μM group showed an overall lower blood glucose after transplantation (p = 0.02), and at the end of the study blood glucose values were reduced compared with transplantation day (15.7 ± 3.6 vs. 32.5 ± 0.5 mmol/L, p = 0.001). In contrast, blood glucose was not significantly changed in control and z-VAD.fmk 200 μM groups. Four weeks after transplantation beta cell mass was higher in z-VAD.fmk 500 μM group (0.15 ± 0.02 mg) than in the control group (0.10 ± 0.02 mg) (p = 0.043). In summary, the treatment of freshly isolated islets with the caspase inhibitor z-VAD.fmk reduced the subsequent apoptosis of the islets once they were transplanted and improved the outcome of the graft