Showing papers on "Thunderstorm published in 1985"
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01 Jan 1985
TL;DR: In this paper, the authors present an overview of the Earth and its atmosphere, including the following: 1. Earth and Its Atmosphere. 2. Earth's Changing Climate. 3. Seasonal and Daily Temperatures. 4. Atmospheric Humidity. 5. Air Pressure and Winds. 6. Stability and Cloud Development. 7. Precipitation.
Abstract: 1. Earth and Its Atmosphere. 2. Energy: Warming the Earth and the Atmosphere. 3. Seasonal and Daily Temperatures. 4. Atmospheric Humidity. 5. Condensation: Dew, Fog, and Clouds. 6. Stability and Cloud Development. 7. Precipitation. 8. Air Pressure and Winds. 9. Wind: Small-Scale and Local Systems. 10. Wind: Global Systems. 11. Air Masses and Fronts. 12. Middle-Latitude Cyclones. 13. Weather Forecasting. 14. Thunderstorms. 15. Tornadoes. 16. Hurricanes. 17. Earth's Changing Climate. 18. Global Climate. 19. Air Pollution. 20. Light, Color, and Atmospheric Optics.
574 citations
TL;DR: In this article, a three-dimensional numerical kinematic cloud model employing Doppler wind fields is developed and used to diagnose temperature and mixing ratios within a thunderstorm, which includes stochastic coalescence effects in warm clouds as well as well-and variable-density dry hail growth.
Abstract: The air flow in convective storms, the force that regulate the flow, and the processes that produce hydrometeors of various kinds are all being studied intensively by meteorologists using Doppler radar observations. The research reported here proceeds from the observed motion through accompanying thermodynamic and micro-physical processes to the analysis of hydrometer content and thermal fields in thunderstorms. A three-dimensional numerical kinematic cloud model employing Doppler wind fields is developed and used to diagnose temperature and mixing ratios within a thunderstorm. The microphysical parameterization includes stochastic coalescence effects in warm clouds as well as well- and variable-density dry hail growth. Known fields from a dynamically simulated cloud are used to establish the accuracy of the retrieval scheme. Real data tests indicate good agreement between retrieved and observed radar reflectivities, qualitative dynamic consistency between observed winds and retrieved buoyancies,...
209 citations
TL;DR: In this article, a control and an x-ray detector were flown into thunderstorms in 1984 and the detector found statistically significant radiation flux increases in the energy range 5 to > 110 keV for time intervals of several seconds each.
Abstract: A control and an x-ray detector were flown into thunderstorms in 1984. The x-ray detector found statistically significant radiation flux increases in the energy range 5 to > 110 keV for time intervals of several seconds each. Simultaneously the control detector showed no statistically significant changes. The x-ray flux is sometimes seen to increase prior to observed lightning discharges and then return to background levels within 0.1 seconds of a lightning flash initiation. The temporal development of these x-ray bursts is discussed and related to inferring the scale size of the x-ray emitting regions.
193 citations
TL;DR: In this article, a squall line exhibiting an extensive trailing region of stratiform precipitation passed over the observational network of the National Severe Storms Laboratory on 22 May 1976, and satellite imagery and conventional radar observations document its evolution from a broken line of thunderstorms to a system of mesoscale proportions, and single-Doppler radar observations describe aspects of its mature structure.
Abstract: A squall line exhibiting an extensive trailing region of stratiform precipitation passed over the observational network of the National Severe Storms Laboratory on 22 May 1976. Satellite imagery and conventional radar observations document its evolution from a broken line of thunderstorms to a system of mesoscale proportions, and single-Doppler radar observations describe aspects of its mature structure. Satellite measurements of cloud-top temperature showed the system to be a mesoscale convective complex (MCC). The life cycle of the system exhibited the stages of development seen in tropical cloud clusters. At maturity, two prominent mesoscale flow regimes were identified at midlevels: one marked by inflow into the system's front and continuing toward its rear, and another associated with inflow entering the extreme rear of the system. The rear inflow was associated with a cyclonic midlevel vortex in the stratiform precipitation region. It produced a concavity, or “notch”, in the back edge of th...
171 citations
TL;DR: In this paper, the characteristics of approximately 75 000 severe thunderstorms which occurred in the United States from 1955 through 1983 are analyzed in an attempt to rectify this situation, and the distribution of over 29 000 storms causing hail larger than 19 mm shows marked diurnal, seasonal, and geographic preferences.
Abstract: While the climatology of excessive rain and tornadoes is well-documented, little is known of storms that produce high winds or large hail. The characteristics of the approximately 75 000 severe thunderstorms which occurred in the United States from 1955 through 1983 are analyzed in an attempt to rectify this situation. The distribution of over 29 000 storms causing hail larger than 19 mm shows marked diurnal, seasonal, and geographic preferences. These storms occur most frequently during the midafternoon hours of May and June in a zone running from central Texas to Nebraska. Spring storms tend to occur south of the Kansas-Nebraska border and summer storms north of it. Thunderstorm winds which produce either “structural” damage or are reported as faster than 25.8 m s−1 generated about 46 000 reports. These storms typically occur during midafternoon in June and July. While the geographic distribution of violent windstorms is similar to that hailstorms, a zone of weaker severe thunderstorm gusts lie...
125 citations
TL;DR: In this article, a series of three rockets was launched over an air mass thunderstorm off the eastern seaboard of Virginia while simultaneous stratospheric and ground-based electric field measurements were made.
Abstract: On August 9, 1981, a series of three rockets was launched over an air mass thunderstorm off the eastern seaboard of Virginia while simultaneous stratospheric and ground-based electric field measurements were made. The conductivity was substantially lower at most altitudes than the conductivity profiles used by theoretical models. Direct current electric fields over 80 mV/m were measured as far away as 96 km from the storm in the stratosphere at 23 km altitude. No dc electric fields above 75 km altitude could be identified with the thunderstorm, in agreement with theory. However, vertical current densities over 120 pA/sq m were seen well above the classical 'electrosphere' (at 50 or 60 km). Frequent dc shifts in the electric field following lightning transients were seen by both balloon and rocket payloads. These dc shifts are clearly identifiable with either cloud-to-ground (increases) or intercloud (decreases) lightning flashes.
119 citations
TL;DR: In this article, the first simultaneous electric field observations performed in the ionosphere and atmosphere over an active nighttime thunderstorm are reported, which implies either considerable Joule heating occurs or a collective instability is present because of the high drift velocities induced by the transient electric fields.
Abstract: The first simultaneous electric field observations performed in the ionosphere and atmosphere over an active nighttime thunderstorm are reported here. In the stratosphere, typical storm-related dc electric fields were detected from a horizontal distance of about 100 km, and transient electric fields due to lightning were measured at several different altitudes. In the ionosphere and mesosphere, lightning-induced transient electric fields in the range of tens of millivolts per meter were detected with rise times at least as fast as 0.2 ms and typical duration of 10-20 ms. The transients had significant components parallel to the magnetic field at 150 km altitude. This implies that either considerable Joule heating occurs or a collective instability is present because of the high drift velocities induced by the transient electric fields. Copious numbers of whistlers were generated by the storm and were detected above but not below the base of the ionosphere. The outline of a new model for direct whistler wave generation over an active thunderstorm is presented based on these observations. The intensity of the observed two-hop whistlers implies that they were amplified along their propagation path and suggests that particles were precipitated in both hemispheres.
105 citations
TL;DR: In this paper, the Klemp-Wilhelmson 3D numerical cloud model is used to investigate cloud development along intersecting thunderstorm outflow boundaries, where the model initial environment is characterized by a temperature and moisture profile typically found in strong convective situations, and the initial wind field is prescribed by a constant unidirectional shear 2.9 m s−1 km−1 from 0.8 to 8.9 km.
Abstract: The Klemp–Wilhelmson three-dimensional numerical cloud model is used to investigate cloud development along intersecting thunderstorm outflow boundaries. The model initial environment is characterized by a temperature and moisture profile typically found in strong convective situations, and the initial wind field is prescribed by a constant unidirectional shear 2.9 m s−1 km−1 from 0.8 to 8.9 km, with a constant wind everywhere else. The wind shear vector is perpendicular to the line containing the two initial outflow-producing clouds (which are spaced 16 km apart and are triggered by thermal impulses centered at the top of the boundary layer). The dynamics of the outflow collision are documented using time-dependent, kinematic air parcel trajectories and thermodynamic data. We find that ambient air in the outflow collision region is literally “squeezed” out of the way as the two outflows collide. Some of this air is lifted to saturation, triggering two convective clouds. The upshear member of the...
105 citations
TL;DR: Starting times of thunderstorms for 450 stations in the conterminuos United States for a 25-year period were analyzed using harmonic analysis techniques as mentioned in this paper, which indicated that the country can be divided into nine thunderstorm regions.
Abstract: Starting times of thunderstorms for 450 stations in the conterminuos United States for a 25-year period were analyzed using harmonic analysis techniques. Diurnal variations were expressed as both the time of maximum storm occurrence and the concentration of activity around this time. Distinct seasonal and spatial variations in diurnal activity occur. Analysis of these variations indicates that the country can be divided into nine thunderstorm regions. In the central states the majority of storms occur at night, but storms are frequent at any time. In both the east and the west there is a marked concentration of storms in the afternoon. In the west and northeast winter storms are rare, while along the Pacific Coast summer thunder is uncommon.
88 citations
TL;DR: In this paper, the contributions of line squalls, thunderstorms and ordinary monsoons to the total rainfall and their variations with latitude are investigated using data from five Nigerian stations for a five year period.
Abstract: Using thunderstorm and rainfall information from five Nigerian stations for a five year period, the separate contributions of line squalls, thunderstorms and ordinary monsoons to the total rainfall and their variations with latitude are investigated. Total and thunderstorm rainfall decreases with increasing latitude but monsoon precipitation decreases exponentially while line squall rainfall is at a maximum around 9°N. Rainfall from thunderstorms shows a single annual peak in July/August at stations north of about 8°N whereas line squall precipitation exhibits a double maximum for all stations south of 12°N. It is also shown that, in the mean, line squalls are the most important rain producing systems, giving 47-6 per cent of the mean total annual precipitation compared with 39 per cent and 13-4 per cent from thunderstorms and ordinary monsoon rain, respectively.
87 citations
TL;DR: In this article, the authors explored the effectiveness of severe thunderstorm detection in the Midwestern region of the U.S. by means of approximately 5-min interval geosynchronous satellite data.
Abstract: In the present exploration of the effectiveness of severe thunderstorm detection in the Midwestern region of the U.S. by means of approximately 5-min interval geosynchronous satellite data, thunderstorms are defined in IR data as points of relative minimum in brightness temperature T(B) having good time continuity and exhibiting a period of rapid growth. The four parameters of rate of T(B) decrease in the upper troposphere and stratosphere, isotherm expansion, and storm lifetime minimum T(B), are shown to be statistically related to the occurrence of severe weather on four case study days and are combined into a Thunderstorm Index which varies among values from 1 to 9. Storms rating higher than 6 have a much higher probability of severe weather reports, yielding a warning time lead of 15 min for hail and 30 min for the first tornado report.
TL;DR: In this paper, a method for retrieval of pressure and buoyancy distributions in deep convection is applied to Doppler radar data collected at two analysis times during the tornadic Del City (Oklahoma) thunderstorm of 20 May 1977.
Abstract: A method for retrieval of pressure and buoyancy distributions in deep convection is applied to Doppler radar data collected at two analysis times during the tornadic Del City (Oklahoma) thunderstorm of 20 May 1977. Change of a previous version of the technique, necessitated by application to real data, include procedures for handling irregularly-bounded volumes and missing data and new assumptions to include reflectivity data and turbulent effects in the equations. Internal consistency cheeks on the quality of retrieved pressure fields imply that the input data are generally of good quality and point out times and heights within the storm at which greater confidence can be placed in the derived fields. In the pretornadic stage the pressure distribution includes at each level a high–low couplet across the updraft with the maximum pressure gradient generally oriented along the environmental shear vector at that altitude. These results are in agreement with predictions of linear theory. Locations of...
TL;DR: The role of the thundercloud in the global electric circuit has been considered by many researchers as discussed by the authors, and the need exists for the development of a numerical regional model capable of resolving small-scale phenomena so that their coupling into the global-scale circuit can be examined.
Abstract: The role of the thundercloud in the global electric circuit has been considered by many researchers. Thus, Holzer and Saxon (1952) have constructed a simple model of a bipolar thunderstorm. The global models considered provide insight into the atmospheric electric circuit but are restricted, both by various analytical mathematical representations and by computer size, to a grid of about five degrees in latitude and longitude. A need exists, therefore, for the development of a numerical regional model capable of resolving small-scale phenomena so that their coupling into the global-scale circuit can be examined. The construction of a two-dimensional quasi-static numerical model of atmospheric electricity is discussed. The model provides a basis for the calculation of the global electric field and current distribution produced by a single thunderstorm generator. In connection with the calculations, the thunderstorm was defined by a quasi-static current source function which generates a dipole charge configuration.
TL;DR: In this article, the downburst weather phenomenon produces a flow like that of a jet directed vertically downward at the ground, and the resulting velocity field near the ground has been modeled as a classical ideal fluid flow generated by a suitable singularity distribution.
Abstract: The downburst weather phenomenon produces a flow like that of a jet directed vertically downward at the ground. The resulting velocity field near the ground has been modeled as a classical ideal fluid flow generated by a suitable singularity distribution. The resulting model of horizontal, lateral, and vertical winds near the ground is quite realistic, and very useful for investigating landing and takeoff of airplanes under downburst conditions. It can be used both for analysis and on-line real-time simulations.
TL;DR: In this paper, the authors presented an interpretation of triple Doppler radar observations of a thunderstorm that occurred at the Kennedy Space Center, Florida, where the main feature of the particle motion field is the persistence, at nearly the same altitude throughout the entire period of analysis, of a zero value of the precipitation particle mean vertical velocity.
Abstract: The paper presents interpretation of triple Doppler radar observations of a thunderstorm that occurred at the Kennedy Space Center, Florida. Precipitation particle motions inside the storm, as evaluated from the three radial velocity radar data sets, are presented in a selected vertical plane throughout the storm development. These data are interpreted and compared with observations of VHF radio emission sources and lightning charge centers derived from an earlier analysis (Krehbiel, 1981). The main feature of the particle motion field is the persistence, at nearly the same altitude throughout the entire period of analysis, of a “balance level” characterized by a zero value of the precipitation particle mean vertical velocity. Further analysis based on considerations of radar reflectivity and air velocity suggests the presence, at this altitude, of relatively large precipitation particles suspended in an updraft. The lightning negative charge centers appear to be less than 1 km above the particle balance level.
TL;DR: In this paper, it was shown that the source current flowing out from a model thunderstorm cloud extends within an area ∼±100 km in the horizontal distance in fair weather, and the global circuit theory using the spherical harmonic function was reviewed to understand the global spreading of the thunderstorm-produced electrical potential.
Abstract: Large-scale fair-weather electricity is reviewed. First, it is shown that the source current flowing out from a model thunderstorm cloud extends within an area ∼±100 km in the horizontal distance in fair weather. Next the global circuit theory using the spherical harmonic function is reviewed to understand the global spreading of the thunderstorm-produced electrical potential. Then the quantitative estimation of global distribution of the electric field and the air-earth current is made by a simple equipotential ionospheric model to see responses to changes of atmospheric conductivity and condensation nuclei. It is then shown where transition of the fair-weather electricity from the local type to the global type occurs. Recent topics on large electric fields measured in the middle atmosphere by using rockets and the international cooperation effort hosted by the atmospheric research group at the University of Wyoming are mentioned last.
TL;DR: In this paper, the authors examined the atmospheric structure associated with wave cyclones that produced 585 severe weather events and found that the most likely location for severe weather is near the central part of the comma tail.
Abstract: Sixty-eight comma-cloud systems over the Great Plains during two spring seasons were examined using satellite imagery and rawinsonde data. Composite soundings were produced for each of ten distinct parts of the comma cloud in order to describe quantitatively the atmospheric structure associated with wave cyclones that produced 585 severe weather events. Composite sectionals and soundings document the different kinematic and thermodynamic environment of each part of the comma-cloud system. Relative-wind, isentropic analyses show air flow relative to the storm and provide additional evidence that the clear region intruding northward east of the cyclone center is an area of strong ascent of dry air with a previous history of subsidence. Stability computations from the mean soundings suggest that the most likely location for severe weather is near the central part of the comma tail, in agreement with the tabulated severe weather reports. A case study from 21–22 March 1981 is conducted to investigate ...
TL;DR: In this article, an analysis of the many possible processes acting within a thunderstorm that can result in the separation of electric charge was presented, and it was concluded that only those involving collisions between ice crystals and small hail pellets can account for the observed high fields and lightning.
Abstract: An analysis is presented of the many possible processes acting within a thunderstorm that can result in the separation of electric charge, and it is concluded that only those involving collisions between ice crystals and small hail pellets can account for the observed high fields and lightning. The fundamental physical processes causing the charge transfer when the ice particles interact remain to be identified, but it appears that differences in contact potential of ice formed in different ways in the atmosphere may be important.
TL;DR: In this paper, the effects of vertical wind shear variations on cloud development along intersecting thunderstorm outflow boundaries are examined. But the model results show that the intensity and the time interval between successive cell updraft maxima of the first two clouds along the collision line are triggered by the outflow colli...
Abstract: In this second paper in a series on outflow interactions, we use the three-dimensional model described in Part I to examine the effects of vertical wind shear variations on cloud development along intersecting thunderstorm outflow boundaries. Three wind shear profiles are used in this study: shear only above cloud base, shear only below cloud base, and shear both above and below cloud base. As in Part I, the shear is unidirectional and is oriented perpendicular to the line containing the two initial outflow-producing clouds (which are spaced 16 km apart). Using the environmental thermodynamic structure from the control simulation in Part I, we vary the shear magnitude in each profile and examine the properties of cloud development in the region where the two outflows collide (the outflow collision line or CL). The model results show that the intensity and the time interval between successive cell updraft maxima of the first two clouds along the CL (both of which are triggered by the outflow colli...
TL;DR: In this article, an observation of a cold front which passed over the Florida peninsula and produced a rope cloud visible on satellite imagery is presented, and the low level structure of the leading edge of the front is revealed with data from the 150 m tower at Cape Canaveral Air Force Station.
Abstract: Observations are presented of a cold front which passed over the Florida peninsula and produced a rope cloud visible on satellite imagery. The low level structure of the leading edge of the front is revealed with data from the 150 m tower at Cape Canaveral Air Force Station. It is shown that the leading edge of the front is very similar to thunderstorm gust fronts and the speed is predicted well by the gust front speed equation. This indicates that the rope cloud is directly analogous to the arc cloud sometimes observed along thunderstorm gust fronts. Further, the rope cloud appears to be a less intense manifestation of the forced convection that produces the narrow cold‐frontal rainbands observed in some other cold front studies.
TL;DR: In this paper, the time-development of the pattern of the average J→m over a relatively large area was studied for one Florida thunderstorm, in good agreement with radar echoes and the locations of lightning charges, and can now be used in further studies of thunderstorm electricity.
TL;DR: The principle of operation of an instrument designed for automatic long-term measurement of the cloud flash to ground flash ratio in thunderstorms is described in this article, which uses a simple antenna to detect the electric field of lightning and is designed to have an effective range of about 14 km and a maximum range of approximately 20 km.
Abstract: The principle of operation of an instrument designed for automatic long-term measurement of the cloud flash to ground flash ratio in thunderstorms is described. The instrument uses a simple antenna to detect the electric field of lightning and is designed to have an effective range of about 14 km and a maximum range of about 20 km. Wave-shape feature measurement is used to distinguish between the electric field wave-shapes corresponding to cloud and ground flashes and is based principally on the presence of relatively large, well-spaced, positive-going changes (R changes) in the field changes caused by ground flashes. From observations with the instrument over two thunderstorm seasons from September 1982 to May 1984 in Brisbane, Australia, the cloud flash to ground flash ratio was 3.0. Large variations were observed in the ratio of cloud flashes to ground flashes for individual thunderstorm days. For days on which at least 100 total registrations occurred, the range was 0.9 to 24.7. Possible applications of an instrument of this type in atmospheric electricity studies are discussed.
TL;DR: In this article, it was shown that positive cloud-to-ground flashes often have return strokes similar to those in negative cloud to ground flashes, except for polarity; that most often there is only a single return stroke; and that often a continuing current of large amplitude, or possibly a discharge in the cloud, follows the return stroke.
Abstract: Cloud-to-ground lightning discharges have been studied for more than 50 years by means of visual, photographic, and electromagnetic observations as well as direct measurements of current. One of the first questions to be addressed was that of the sign of net effective charge transferred to earth. The conventional wisdom on the subject has been that most cloud-to-ground lightning flashes transfer net negative charge from cloud to ground. There is also evidence that up to one third of the flashes observed in a given study could transfer net positive charge to earth. Both the subject of positive charge transfer to earth in general and the subject of positive return strokes received attention by Workman, Brook, and others in New Mexico occasionally over the last 30 years. Relatively recently, there have been increasingly numerous reports of cloud-to-ground lightning that transfers positive charge to earth in winter thunderstorms in Japan, in summer thunderstorms in Scandinavia, in severe storms in the U.S. Great Plains, in summer thunderstorms in the western United States, in summer thunderstorms in Florida, and in fall and winter thunderstorms in the northeastern United States. Furthermore, from the most recent observations it appears that positive cloud-to-ground flashes often have return strokes similar to those in negative cloud-to-ground flashes, except for polarity; that most often there is only a single return stroke; and that often a continuing current of large amplitude, or possibly a discharge in the cloud, follows the return stroke.
TL;DR: In this paper, the column abundances of lightning-produced CO, C2H2, and HCN were computed using the lightning energy dissipation rate on Jupiter from Voyager's observation, together with shock-tube experimental results and reasonable eddy diffusion coefficients for the various atmospheric layers, to compute the column abundance of lightning produced CO, H2, C 2H2.
TL;DR: In this article, a NASA U-2 airplane flying over nocturnal thunderstorms showed frequent lightning activity in the upper part of the cloud, where unobscured segments of lightning channels 1 km or longer are visible in clear air around and above the cloud.
Abstract: Photographs from a NASA U-2 airplane flying over nocturnal thunderstorms show frequent lightning activity in the upper part of the cloud. In some cases, unobscured segments of lightning channels 1 km or longer are visible in clear air around and above the cloud. Multiple images of lightning channels indicate multiple discharges in the same channel. Photographs taken through a diffraction grating show that the lightning has a spectrum similar to that observed in the lower troposphere. Lightning spectra obtained with a slitless line-scan spectrometer show strong singly ionized nitrogen emissions at 463.0 and 500.5 nm. Field changes measured with an electric field-change meter correlate with pulses measured with a photocell optical system. Optical signals corresponding to dart leader, return stroke, and continuing current events are readily distinguished in the scattered light emerging from the cloud surface. The variation of light intensity with time in lightning events is consistent with predicted modification of optical lightning signals by clouds. It appears that satellite based optical sensor measurements cannot provide reliable information on current rise times in return strokes. On the other hand, discrimination between cloud-to-ground and intracloud flashes and the counting of ground strokes is possible using the optical pulse pairs which have been identified with leader, return-stroke events in the cloud-to-ground flashes studied.
TL;DR: In this article, the authors measured the mass, moisture and energy sources associated with individual cumulus congestus and thunderstorm clouds using an instrumented aircraft and showed the important role of mixing in producing downdrafts.
Abstract: Apparent mass, moisture and energy sources associated with individual cumulus congestus and thunderstorm clouds are measured using an instrumented aircraft. The results for thunderstorms are similar to those obtained by other investigators. Cumulus congestus clouds differ greatly from thunderstorms and show the important role of mixing in producing downdrafts. The thunderstorm profiles are strongly affected by precipitation-induced downdrafts.
TL;DR: In this article, a two-part evaluation of 30 forecasts by a mesoscale numerical weather prediction model (MASS 2.0) is presented, and examples of model 'forecasts' of intense convective storm clusters, a severe squall line triggered along a dryline, orographically induced hailstorms, and sea breeze thunderstorms are provided.
Abstract: The mesoscale part of a two-part evaluation of 30 forecasts by a mesoscale numerical weather prediction model (MASS 2.0) is presented. Unfiltered fields are combined into convective predictor fields, the loci of which are then related at two-hour intervals to the loci of strong mesoscale convective systems identifiable in national radar summary plots and GOES satellite imagery. Examples of model 'forecasts' of intense convective storm clusters, a severe squall line triggered along a dryline, orographically induced hailstorms, and sea breeze thunderstorms are provided.
TL;DR: Anomalously large short-term ozone concentrations were observed on several occasions by aircraft during an experiment on 5 August 1980 to characterize the physical and chemical properties of the Baltimore urban plume as discussed by the authors.
TL;DR: In this article, Nisbet et al. used a computer model to evaluate the role of thunderstorm clouds in generating the currents necessary for the maintenance of the ionospheric potential and found that the most important single variable controlling the ionosphere current/generator current ratio for both very active storms and for storms that do not produce lightning is the height of the lower active center.
Abstract: A computer model (Nisbet, 1983) was used to evaluate the role of thunderstorm clouds in generating the currents necessary for the maintenance of the ionospheric potential. The effects of variations in the breakdown electric field below the lower charge center, heights of the upper and lower charge centers, generator currents and geometry, as well as of the conductivity profile of the cloud, the surrounding air, and the ionosphere, on the currents to the ionosphere were examined. It was shown that the most important single variable controlling the ionospheric current/generator current ratio for both very active storms and for storms that do not produce lightning is the height of the lower active center. The ionospheric conductivity has a negligible effect on the total current to the ionosphere, although it is very important in controlling the electric field and current density waveforms above the cloud.