ICAE International Commission on Atmospheric Electricity

ICAE 2003 Versailles

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and Poster Format


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Friday 11th June



Session F2 Global Lightning and Climate II (poster)


A. G. Amiranashvili, V. A. Amiranashvili, Z. A. Chumburidze, B.S.Beritashvili and I.P.Mkurnalidze
Some Characteristics of a Thunderstorm Activity in Georgia

R. Barreto Biasi Gin, C. Beneti
Cloud-to-ground lightning flashes in South and Southeastern Brazil in 2001: case study
  R. Barreto Biasi Gin, C. Beneti
Cloud-to-ground lightning flash density in South and Southeastern of Brazil:1999-2002
D. J. Boccippio
Automated classification of storm flashing/non-flashing condition from microphysical and environmental observations
  W. L. Boeck, A. R. Jacobson, H. J. Christian, and S. J. Goodman
Multi-Satellite Observations of Oceanic Lightning
  V. Gorbatenko, A. Dulzon, I. I. Ippolitov, M. V. Kabanov, S. V. Loginov and T. V. Ershova
The structure of long-term series of number of thunderstorm days
  S. S. Kandalgaonkar, M. I. R. Tinmaker, and A. Nath
Characteristics of lightning flashes over the Indian region
  P. Lalande, A. Bondiou-Clergerie, P. Blanchet, F. Roux, and S. Chauzy
ORAGES: A micro-satellite to detect and locate the lightning VHF emissions from space
  T. E. Light , S. M. Davis, W. Boeck, A. R. Jacobson, and D. M. Suszcynsky
Global optical lightning flash rates determined with the Forte Satellite
  P. Ortéga, M. Rodière, V. Laurent
Lightning activity, stability indices and climatic anomalies over Tahiti Island
  C. Price, M. Asfur, W. Lyons, and T. Nelson
An improved ELF/VLF Method for Globally Geolocating Sprite-producing Lightning
  G. Sątori and B. Zieger
Areal Variations of the Worldwide Thunderstorm Activity on Different Time Scales as Shown by Schumann Resonances
  G. Sątori
On the Dynamics of the North-South Seasonal Migration of Global Lightning
  D. M. Suszcynsky, T. J. Fitzgerald, M. J. Heavner, A. R. Jacobson, T. E. Light, M. B. Pongratz, and C. T. Rhodes
The detection of VHF lightning from GPS orbit
  G. Strandberg, S. Israelsson and U. Andersson
Lightning discharges in Sweden and along the Swedish coast line
  X. Qie and R. Toumi
Lightning Activities on Tibetan Plateau as Observed by Lightning Imaging Sensor
  E. Williams, V. Mushtak and D. Boccippio
Another Look at the Dependence of Lightning Flash Rate on the Temperature of Boundary Layer Air in the Present Climate


Some Characteristics of a Thunderstorm Activity in Georgia

A.G.Amiranashvili, V.A. Amiranashvili, B.S. Beritashvili, I.P. Mkurnalidze
Institute of Geophysics, Georgian Academy of Sciences

Hydrometeorological Service of Georgia


Some results of the analysis of data of instrumental observations on cloud thunderstorm activity in eastern Georgia (Alazani valley, 1978-1984 and Dusheti , 1971-1973) have been presented. In Alazani valley, measurements of lightning discharges to the ground were performed by surface network of electrostatic fluxmeters, total number of lightnings has been recorded by PRG-15 type meters of near discharges and radiolocation parameters of clouds were measured by ARS, MRL-2 and MGL-5 types of radars. In Dusheti, total number of lightning discharges was recorded by PRG-15.

In Alazani valley, average altitude of charges, involved in the lightning discharge, makes 6.7km (7.5 km for positive charges and 6.5- for negative ones). Correlation between intra-cloud discharges and charges to the ground is approximately 2.2. Correlation between the intensity of discharges of Ng to the ground and the maximum altitude of a cloud echo Hm, has a shape of :
Ng = 0,00052 Hm^3.273 min^-1 (Hm in km).

Empirical link of Ng with a radiolocation parameter of thunderstorm danger R=HmHzlgZ/Ho^2 (where Hz is an altitude of maximum reflectivity, Ho-an altitude of a zero isotherm) is sufficiently described by the following relation:
Ng = 0,068R-0,25 min^-1

Average intensity of a total number of discharges during a warm six-month period of the year in Alazani valley makes 0,0017 discharge/minkm^2, and in Dusheti - 0.0014 discharge/minkm^2.

Charge Q, carried away from a cloud by a lightning discharge, is connected with Hm and R in the following way:
Q=-0.567Hm^3+14.44Hm^2-116.5Hm+308.2  C min^-1
Q=-0.196R^2+6.7R-33 C min^-1

By the growth of thunderstorm activity, hail activity of convective clouds is increasing, as well.Connection of a radiolocation probability of hail-fall K with Ng is expressed as:
K=177.8 Ng^3-391.1Ng^2+286.Ng-55.12

According to Dusheti data mean monthly daytime intensity of thunderstorm discharges Y is in direct correlation with a thunderstorm day duration X1 and a value of beta-radioactive fall-out X2, and in inverse correlation with atmosphere aerosol pollution X3 (correlation coefficients are equal to 0,62, 0.5 and -0,54 respectively). The data on X2 have been taken for Tbilisi. X3 are the values of aerosol optical depth of the atmosphere in Tbilisi. Due to the nearness of Dusheti to Tbilisi the values of X2 for these two points are the same, and atmosphere pollution in the vicinity of Dusheti is directly proportional to X3. Dimensionality of X1 variation is from 70 to 185 min, that of X2-from 1.5 to 25.9 Bq/m^2 day, X3-from 0.109 to 0.197. Connection of Y with X1, X2 and X3 has the following appearance:
Y=1.0676 X1+0.7592X2-718.86X3+85.447

The latter shows, that under certain circumstances, the atmosphere aerosol pollution can abate thunderstorm discharge intensity.


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Cloud-to-ground lightning flash density in South and Southeastern of Brazil:

Rosangela Barreto Biasi Gin
University of Inaciana Educational Foundation, FEI, Sao Paulo, Brazil

Cesar Beneti
Technological Institute SIMEPAR, Curitiba – Parana, Brazil


Cloud-to-ground lightning flash density results of south-southeastern Brazil have been analyzed from period of 1999 through 2001. About 10 million of cloud-to-ground (CG) lightning flashes were recorded in Sao Paulo and Parana. Annual ground flash density and median peak current for negative and positive flashes have been analyzed. Observed CG lightning flashes were predominantly negative. Flash density varies from less than 4 to values over 14 flashes/km 2 /yr. The maximum flash density is similar to results obtained in Florida. Observed median negative peak current and median positive peak current were 25kA and 35kA, respectively.

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Cloud-to-ground lightning flash density in South and Southeastern of Brazil:

Rosangela Barreto Biasi Gin
University of FEI, Departamento de Física,
Av Humberto ªCastelo Branco,3972 , São Bernardo do Campo, São Paulo, Brazil,

Cesar Beneti


Cloud-to-ground lightning flash density results from São Paulo and Paraná, Brazil, have been analyzed during the period from 1999 through 2002. The geographical distribution of total flashes, average peak current and positive flashes have been analyzed too. Monthly mean maps were constructed from a database of about 16 million of cloud-to-ground (CG) lightning strikes recorded by a Lightning Positioning and Tracking Systems LPATS. The total of CG lightning strikes recorded are predominant negative flashes (80%). The maximum flash activity occurs in October and in February coinciding with the dominete storms in the spring season and warm season respectively These months presented greater flash density and regions of great cloud_to_ground lightning impact.

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Automated classification of storm flashing/non-flashing condition from microphysical and environmental observations

Boccippio, Dennis J.,
NASA / Marshall Space Flight Center, SD-60, Marshall Space Flight Center, AL 35812
(256)-961-7909 (V) (256)-961-7979 (F)


Three years of paired TRMM radar, passive microwave, lightning and NCEP reanalysis variables are used to answer the question: "Can we classify a storm as flashing, or not, based only on microphysical and environmental observations?". The skill with which we can answer P(f > 0 | X) should provide guidance on the skill we should expect for the harder question, P(X | f), relevant for the use of remotely sensed lightning for data assimilation purposes, and hence numerical forecast improvement.

Simple univariate threshold rules, linear multivariate discriminant analysis, generalized linear models and nonlinear neural networks (NN) are tested. The database is split into training/validation and test subsets to prevent overfitting; over land, approximately 160000 "cold" (15 dBZ echo top < 0C) storms are used in each subset, with ~7% of these flashing. Skill is assessed using the Heidke Skill Score HSS (unbiased total skill), Gilbert Score GS (unbiased critical success index), Probability of Detection, False Alarm Rate, and bias.

Optimized radar univariate threshold rules ("30 dBZ echo tops colder than -17C", or "maximum reflectivity at -20C greater than 29 dBZ") have surprisingly good global (35S-35N, land) skill:
HSS/GS/POD/FAR = 0.76/0.62/0.78/0.22.
However, they exhibit regional bias (arid regions have too many misses; maritime regions, too many false alarms). Passive microwave rules ("85 GHz minimum brightness temperature colder than 222K") have slightly lower (0.70/0.54/0.72/0.29) skill. Multivariate models improve overall skill by only 3-5%, but mitigate both model and regional bias. A "kitchen sink" TRMM+NCEP NN classifier achieves highest global skill (0.80/0.67/0.83/0.19). The NN has the attractive property that high skill is maintained over a wide range of decision thresholds, allowing POD/FAR tradeoff if the cost of over- or underwarning is task-specific.

Univariate rules' skill over open oceans is significantly lower (at best 0.54/0.37/0.54/0.46) and more intensive optimization of multivariate approaches may be required to yield useful diagnostic models over oceans.


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Multi-Satellite Observations of Oceanic Lightning

W. L. Boeck
Niagara University, Niagara University,
365 N 7th St, Lewiston, NY 14092

A. R. Jacobson
Los Alamos Natiional laboratory, Space & Atmospheric Sciences Group, Los Alamos, NM 87545

H. J. Christian, S. J. Goodman
Global Hydrology & Climate Center, NASA Marshall Space Flight Center,
Huntsville, AL 35806


This paper will present several case studies of active oceanic lightning storms. Measurements by instruments on the TRMM and FORTE platforms demonstrate that the two sets of sensors reinforce and complement one another. There is spatial and temporal coincidence between the optical data sets from LIS on TRMM and the photo-diode detector on FORTE. The LIS flash analysis provides a framework to interpret the stroke level data from FORTE. For these cases, the VHF receiver on FORTE is slaved to the optical system to provide stroke level rf diagnostics. The occasions when TRMM and FORTE simultaneously have a lightning storm in their overlapping fields of view are extremely rare.

One case study in the Gulf of Mexico is within range of land based senor networks. These networks confirm the interpretation of satellite data and well as provide context for the storm conditions.


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The Structure of Long-Term Series of Number of Thunderstorm Days

Gorbatenko V., Dulzon A., Ershova T.V.
High Voltage Research Institute at Tomsk Polytechnic,

Ippolitov I. I., Kabanov M. V., Loginov S.V.
Institute for optical monitoring SB RAS, Tomsk, Russia


The global climate change issue has raised serious questions about the potential for changes in weather extremes. The aim of this work is to conduct a research of the periodical structure of temporal ranges (the years 1891-1996) of number of days with thunderstorm on the territories different in its geographical position for to reveal general regularity, which can be connected, to changes in the atmosphere circulation or to any other reasons. It is shown results from analyses of the periodical structure, which displays in dates of forms of atmosphere circulation. Relationship between peculiarity of the atmosphere circulation and thunderstorm activity are studied. Wavelet transform were used in the analysis. Most of parameters exhibit long-term periodicity (greater then 18 years), medium (7-10 years) and short one (2-6 years). On the amplitude of spectral density meanings, medium and short cycles on all the territories are more obvious and are reasoned mostly with the presence of cyclical component in recurrence of synoptical processes, stipulating for thunderstorms. In dates of forms of atmosphere circulation long-term periodicity more brightly displayed.


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Characteristics of lightning flashes over the Indian region

S.S. Kandalgaonkar, M.I.R. Tinmaker and Asha Nath
Indian Institute of Tropical Meteorology, Pune 411 008, India


Satellite (LIS) based lightning flash grid (0.5o x 0.5o) data for 78 Indian observatory stations covering 8o-30oN for a period of 4 years (1998-2001) form the data set for the study. These data have been analyzed to examine their annual, interannual, seasonal and geographical distribution. An attempt has been made to obtain the IC:CG ratio. The result of this study demonstrates that there exists latitudinal variation of lightning flash density, which is also confirmed through seasonal and ratio analysis. The annual variation of lightning flash density exhibits a typical bimodal variation giving the first maximum in the month of May and second in the month of September. Time series of this parameter showed a consistent increase in the peak values. The IC:CG ratio values are found to be more or less equal to the values reported by other investigators for the tropics.


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A micro-satellite to detect and to locate the lightning VHF emissions from space

P. Lalande, A. Bondiou-Clergerie, P. Blanchet,
Onera, 29 Av. de la division Leclerc, 92322 Chatillon, France
Tel: 33 1 46 73 47 63, Fax: 33 1 46 73 41 48, e-mail: lalande@onera.fr

F. Roux, S. Chauzy
Laboratoire d'Aérologie, Toulouse, France


Space based sensors enable continuous observations of the convective activity over the whole earth. The ORAGES project, selected in 1998 by the French space agency (CNES) for a preliminary phase to validate the design concept of the instrument, is designed to locate and detect the VHF emissions of lightning from space with a resolution of 10x10 km. It is based on a broad band VHF interferometer composed of a 5 antenna network with a center frequency of 120 MHz and a diameter of 3. m. This instrument will be aboard a micro-satellite with an orbit of 800 km height and an inclination of 21 degrees which enables an accurate studies of convective regions in the tropical band.
Information provided by ORAGES on the intra-cloud and cloud-to-ground lightning activity within tropical convective systems will be combined with that from ground-based and spaceborne meteorological observing devices, to investigate the processes involved in the evolution of convective systems through the characterization of the regions where dynamic and microphysical processes can sustain electric activity. These results will contribute (1) to understand the atmospheric water cycle leading to precipitation at the earth's surface which strongly modulates the seasonal and geographical variations of climate, (2) to estimate the production of tropospheric Nox and (3) to investigate the physical processes associated with the TIPPs.
In the framework of the preparation of ORAGES, one prototype of the payload has been developed and tested at the end of 2001. In parallel, the relationships between rainfall and electrical activity have been investigated following two directions. The first one consists in analyzing available data from radar, satellite and lightning detection systems. The second item concerns the development of a specific module in the French non-hydrostatic model for atmospheric simulation MésoNH, in order to simulate the electrification of the thundercloud and the development of lightning when the electric field inside the cloud reaches critical value.


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Global optical lightning flash rates determined with the Forte Satellite

T.E. Light, S.M. Davis, A.R. Jacobson, D.M. Suszcynsky
Los Alamos National Laboratory, Space & Atmospheric Sciences Group, Los Alamos, New Mexico 87545

W. Boeck
Niagara University


The FORTE satellite was launched in 1997 and among its sensors is a non-imaging, optical photodiode detector (PDD). The PDD has detected more than 1 million lightning events worldwide since launch. The PDD does not provide precise geolocation information, but rather indicates an event occurred somewhere within the 80-degree field-of-view of the instrument (this corresponds to a roughly 1200 km diameter footprint on the ground). Using PDD observations of nighttime lightning events, we have determined the geographic distribution of nighttime flash rate density. In this work, we first detemine the PDD detection efficiency for total lightning through comparison to lightning observations by the TRMM satellite's Lightning Imaging Sensor (LIS), using cases in which FORTE and TRMM viewed the same storm. We make the assumption that our detection efficiency has no spatial variability throughout FORTE's orbit, and thereby determine total (nighttime) flash rate density maps. We present here both seasonal and total flash rate maps. In particular, we compare our results to previously published global flash rate maps, and also we examine any land-ocean differences in optical flash rate density. Finally, we examine some characteristics of the optical emissions of lightning in both high and low flash rate environments, and over both land and ocean.


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 Lightning activity, stability indices and climatic anomalies over Tahiti Island

Ortéga P., Rodière M.,
Jeune Equipe Terre Océan - University of French Polynesia

Laurent V.
Météo-France - Direction régionale de la Polynésie française


The lightning activity has been recorded during the last five years with the help of a net of CIGRE Lightning Flash Counters installed all around Tahiti island. A mean value of 90 days of thunderstorm per year was records. Furthermore, an extrapolation in time is done for the last thirty years using the registration (keraunic level) of the main meteorological station of Météo-France. Tahiti is a circular mountainous island with a 30km diameter and culminating at 2.200m The effect of the relief on the lightning activity measurement is discussed with the help of satellite photographs. The daily, monthly, seasonal or yearly lightning activity over Tahiti is analysed. FFT analysis revel strong correlations with the cold phase of the ENSO (Niña) and the MJO or the TISO. On other hand, the daily lightning activity is confronted with some meteorological parameters and the various stability indices based on the layer stability concepts (Showalter, Adedokun, Telfer…). The sounding balloons executed twice a day by Météo-France allow the computation of such indices.


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An Improved ELF/VLF Method for Globally Geolocating Sprite-producing Lightning

Colin Price and Mustafa Asfur
Department of Geophysics & Planetary Science, Tel Aviv University, Ramat Aviv 69978, Israel,
tel: 972-3-6406029
fax: 972-3-6409282
e-mail: cprice@flash.tau.ac.il

Walter Lyons and Thomas Nelson
Yucca Ridge Field Station, FMA Research, Inc., Fort Collins, Colorado, USA


The majority of sprites, the most common of transient luminous events (TLEs) in the upper atmosphere, are associated with a sub-class of positive cloud-to-ground lightning flashes (+CGs) whose characteristics are slowly being revealed. These +CGs produce extremely low frequency (ELF) and very low frequency (VLF) radiation detectable at great distances from the parent thunderstorm. During the STEPS2000 field program in the United States, ELF/VLF transients associated with sprites were detected in the Negev Desert, Israel, some 11000 km away. Within a two-hour period on 4 July, 2000, all of the sprites detected optically in the United States produced detectable ELF transients in Israel. All of these transients were of positive polarity (representing positive parent lightning). Using a VLF antenna to obtain the azimuth of the transients, and a separate ELF antenna to calculate the distance between the source and receiver, we remotely determined the position of sprite-forming lightning events with an average locational error of 184 km (error of 1.6%). This allows us to use only a few stations for accurately locating global sprite-producing lightning activity. Using the Yucca Ridge Field Station (Fort Collins, Colorado) optical measurements to verify and calibrate the Negev detection algorithm, we are confident that soon we will be able to map the major source regions of sprite activity continuously from our single Negev station.


Price, C., M. Asfur, W. Lyons and T. Nelson, 2002: An improved ELF/VLF method for globally geolocating sprite-producing lightning, Geophys. Res. Lett., 29(3), 1-1 - 1-4.


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Areal Variations of the Worldwide Thunderstorm Activity on Different Time Scalesas Shown by Schumann Resonances

G. Sátori and B. Zieger
Geodetic and Geophysical Research Institute, Csatkai u. 6-8. H-9400 Sopron, Hungary,
E-mail: satori@ggki.hu


Long-term Schumann resonance frequency records at Nagycenk (NCK), Hungary have been used to determine areal variations of the worlwide thunderstorm activity on seasonal, annual and interannual time scales. The daily frequency range (DFR) of Schumann resonances (SR) is the band in which the resonance frequency shifts up and down during a day. The DFR is related to the size of the region where the random lightning discharges are distributed. The wider, the region is, the smaller the DFR becomes, and vice versa. The mean size (diameter) of thunderstorm regions can be obtained from the DFR using a calibration curve charcteristic of the SR station at NCK. Monthly means of source diameter were determined from May 1993 up to the present. Annual variations with May-June maxima and November-December minima and semiannual variations with April and October maxima were extracted with a filtering technique. The annual areal variation is a response to the north-south asymmetry of the land-ocean distribution. The semiannual areal variation can be explained both by the semiannual tropical land surface temperature variations and the thermal instabilities in the transition seasons (spring and fall). The annual and semiannual areal variations show a clear, long term (decadal) modulation which might be attributed to the dependence of the worlwide lightning area on the 11 year solar-cycle (see Fig.1).


Fig.1. Monthly sunspot number (top panel) and long term (solar cycle) modulation of the annual areal variation of global lightning (bottom panel) deduced from Schumann resonance frequencies recorded at Nagycenk, Hungary



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On the Dynamics of the North-South Seasonal Migration of Global Lightning

G. Sátori
Geodetic and Geophysical Research Institute, Csatkai u. 6-8., Sopron, Hungary,
E-mail: satori @ggki.hu


The daily Schumann resonance (SR) frequency patterns are mainly determined by the lightning source-observer configuration. Four basic types of daily frequency patterns have been distinguished corresponding to the four seasons observed for each SR mode at Nagycenk, Hungary, (See Fig.1). The number of days with similar daily frequency patterns (characteristic for a season) were very different. The same daily frequency patterns (I. type) have been observed during 160-165 consecutive days from the beginning of November to the first part of April in any year of SR observations at Nagycenk. This means that the position of global lightning, centered on the tropics and the Southern Hemisphere in these months, is rather stable with respect to the observer. The northward migration of lightning in the next season is very fast as only about 40-50 daily frequency patterns show similar characters (II. type) in the months April and May. The number of days with the daily frequency pattern of III. type is 90-100 covering the three summer months (June, July, August) in the Northern hemisphere. The migration of lightning is slower southward than in the opposite direction and it takes about 60-70 days as indicated by the daily frequency patterns of IV. type characteristic mainly in September-October. The dynamics of the north-south migration deduced from SR observations was compared with the dynamics of the mean land surface temperature variations measured in those latitudes of the Northern and Southern hemisphere lands where lightnings mainly occur and in the tropical Pacific. The temperature reaches the highest values and remains very stable in the south tropical Pacific for a rather long period just when the diurnal frequency pattern of I.type can be observed. "Cooling" (only about 1-2º C) occurs here in April when global lightning starts its migration to the Northern hemisphere as indicated by SR measurements. Duration of the migration back to the Southern hemisphere coincides with the warming up period in the south tropical Pacific and doesn't fit properly the warming up time in the Southern hemisphere lands. It seems that the dynamics of the north-south lightning migration follows oceanic (Pacific) thermodynamical properties in spite of the fact that the global lightning is mainly concentrated on the lands. This result is in accordance with the meridional redistribution of global lightning as a response to the temperature variations in the tropical Pacific on the ENSO time scale (Sátori and Zieger, GRL, Vol. 26, NO. 10, 1365-1368, May15, 1999 )

Fig. 1. Daily SR frequency patterns grouped on the basis of morphological similarity for the four seasons


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The detection of vhf lightning from gps orbit

D. M. Suszcynsky, T. J. Fitzgerald, M. J. Heavner, A. R. Jacobson, T. E. Light, M. B. Pongratz, C. T. Rhodes
Los Alamos National Laboratory, Space & Atmospheric Sciences Group,
Los Alamos, New Mexico 87545


Over the last few decades, there has been a growing interest to develop and deploy an automated and continuously operating satellite-based global lightning monitor. To date, efforts to develop such a system have focused on the deployment of optical sensors that can provide cost-effective single-platform geolocation of lightning flashes. This paper details an ongoing effort to develop a satellite-based Very High Frequency (VHF) Global Lightning And Severe Storm monitor (V-GLASS) based on the detection of VHF emissions from lightning. The proposed system would be an outgrowth of an already-funded constellation of broadband VHF receivers to be flown on the upcoming Block IIF Global Positioning System (GPS) satellite constellation. The use of an existing VHF sensor constellation would greatly reduce system cost and would allow the community to capitalize on the specific benefits of VHF lightning detection, namely the three-dimensional geolocation of lightning and the potential to identify lightning types (CG vs. IC) based on VHF power profiles.

The conceptual design for the VGLASS system will be presented and expected system performance and capabilities will be discussed in terms of VHF data analysis results from a similar system currently being flown and operated on the SVN 54 GPS satellite. Analysis of data sets from the SVN 54 VHF receiver, the Los Alamos National Laboratory Sferic Array located in Florida, and GOES-8 infrared imagery will be used to show that a GPS-based VHF lightning monitor will preferentially detect impulsive (~1 uS) lightning signatures called narrow bipolar events (NBEs). These lightning signatures are ubiquitous and their occurrence rates, as will be shown, are direct indicators of thunderstorm convective strength.


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Lightning discharges in Sweden and along the Swedish coast line

G. Strandberg
Division of Electricity and Lightning Research, ox 539, 75 2 Uppsala, Sweden

S. Israelsson and U. Andersson
Department of Earth Sciences, Meteorology, Villavägen 6, 752 36 Uppsala, Sweden

Lightning data from the years 1990 – 1999 have been studied and it gives the climatological pattern of the lightning characteristics. An increasing number of ground flashes is observed during the last 10 years. The flash density has a latitudinal variation with higher density in the south and lower in the north. The diurnal variation of thunderstorm activity is also large. Almost everywhere most flashes occur during daytime. Over the sea the thunderstorm activity is, however, most pronounced in nighttime. The negative peak currents show a transition between high average amplitude over the sea and lower average amplitude over land. The average multiplicity for the positive flashes is around almost everywhere. The study shows that the density of lightning strikes is dependent on the underlying surface condition and its characteristics, which vary with season. In summertime there is more lightning strikes observed ashore than in autumn, when the maximum of lightning strikes is moved offshore. Land- and sea-breeze can on the west-coast effect the lightning strikes, when a minimum of lightning strikes is observed directly offshore. A study of a frontal thunderstorm shows that squall-line generates heavy and intensive lightning activity before a frontal thunderstorm arrives.
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Lightning Activities on Tibetan Plateau as Observed by Lightning Imaging Sensor

Xiushu Qie, Ral Toumi
Department o Physics Imperial College London SW7 2BZ

Yunjun Zhou
Cold and Arid Regions Environmental and Engineering Research Institute
Chinese Academy of Sciences Lanzhou Gansu 730000 P. R. China


Lightning lash activities on the central Tibetan Plateau have been studied by using the Lightning Imaging Sensor (LIS) database rom 1998 to 2002. The lightning activity shows a clear diurnal variation on the central Plateau. The lightning discharge is weaker on the Plateau than in other low-altitude continental regions because o the lower convective available poential energy (CAPE) on the Plateau. The CAPE is 12 times lower and the sensitivity o lightning activity to CAPE changes on the Plateau is 30 times more sensitive than other prominent low-altitude regions.

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Another Look at the Dependence of Lightning Flash Rate on the Temperature of Boundary Layer Air in the Present Climate

Parsons Laboratory, MIT, U.S.A,

Parsons Laboratory, MIT, U.S.A,



Considerable empirical evidence has accrued to show that global lightning activity is sensitive to surface air temperature. The physical basis of this sensitivity and which boundary layer temperature one should consider have been subject to question. The present study is concerned with a clarification of these issues by comparing the lightning flash rates of thunderstorms with thermodynamic properties of the air ingested by the same storms. These comparisons are enabled by integrating Lightning Imaging Sensor (LIS) observations from the NASA Tropical Rainfall Measuring Mission (TRMM) satellite with routine surface meteorological observations. Key thermodynamic quantities extracted from the meteorological data are dry bulb temperature, wet bulb potential temperature and cloud base height. Based on comparisons for hundreds of thunderstorms throughout the tropics and subtropics, the dependences of mean flash rate on dry bulb temperature and cloud base height (closely related to dry bulb temperature) are clearly tighter than the flash rate dependence on wet bulb potential temperature. Lightning flash rate increases roughly exponentially with both dry bulb temperature and cloud base height, with an order of magnitude change in flash rate for a change in cloud base height typical of oceans (500 m) to strongly continental values (3000 m). These findings are interpreted by emphasizing the 'dry' origins of moist convection within the planetary boundary layer. Hotter thermals in deeper boundary layers are broader thermals, and are associated with broader updrafts above cloud base. Broader updrafts increase the efficiency of conversion of Convective Available Potential Energy (CAPE). These results also have important implications for the documented contrast in lightning activity between Africa and the "green ocean" of South America.

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