ICAE Fall 2001 News Letter
|Dunedin||45.9 S||170.5 E|
|Perth||32.1 S||115.8 E|
|Brisbane||27.6 S||153.1 E|
|Darwin||12.4 S||130.9 E|
|Singapore||1.3 N||103.8 E|
|Osaka||34.8 N||135.5 E|
At each site I provided and set up the lightning receiver with antenna (a simple vertical whip, about 2 m long) and a PC connected to the internet. The host at each site supplies the internet connection and in return gets free access to the lightning position (and other) data world wide. Only the hosts and their immediate colleagues get this free access, just as if they had bought access or software licenses. I have received invitations to set up my lightning receivers at (or near) the following sites:
Durban 29.9 S 31.0 E Huancayo 12.1 S 75.2 W Agra 27.2 N 78.0 E Tucson 32.3 N 111.0 W Budapest 47.5 N 19.1 E Poker Flat 65.1 N 147.3 W Tromsoe 69.6 N 19.2 E
I hope to set up these during the next (northern hemisphere) summer. These 13 sites are not well distributed. Sites in far east Canada, far east Brazil, and on islands in the main oceans would make this distribution more even and allow full global coverage even when one or two sites are out of action due to power outages and the like. If you would like to be a host and get free access to the data, send me an email to the above address.
Lightning Research Group of Osaka University (hereinafter LRGOU) realized the operational broadband interferometer in two-dimension, and LRGOU operated the system during field campaigns in Darwin, Australia in 2000 and in Hokuriku, Japan in 2001. The broadband interferometer owns two main interesting capabilities. One is the capability to monitor the thunderstorm activity and its movement in a relatively wide range. This capability was confirmed during the Darwin campaign, in which LRGOU took the role of monitoring thunderstorm for Biomass Burning and Lightning Experiment (BIBLE). LRGOU could capture two beautiful thunderstorm activities by the broadband interferometer. The other capability is to locate the VHF radiation sources with quite high time resolution, and the lightning discharge propagation with branching can be visualized. During the winter campaign this function was realized. These achievements have been reported as scientific papers on IEEE Transaction on Instrumentation and Measurement, Geophysical Research Letters, Journal of Atmospheric and Solar-Terrestrial Physics, and IEICE Transaction on Electronics.
LRGOU is concerned with Tropical Rainfall Measuring Mission (TRMM), which is the cooperation between NASA and NASDA, as one of principal investigators of Lightning Imaging Sensor (LIS). By analyzing LIS and Precipitation Radar, LRGOU discovered two interesting issues. One is the discrepancy of lighting activity over Indonesia during El Nino period and ordinary period. It is well known that during El Nino period there is less precipitation over western Indonesia than normal period. On the contrary the lightning activity during El-Nino period is more than during normal period. That means the less precipitation, the more lightning activity. The interpretation of this issue is not obtained yet. The other issue is the parameterization of thunderstorms from the aspects of the global observations. The first discovery was published as one of the articles of Geophysical Research Letters, and the second is now being prepared to submit to a scientific journal.
LRGOU analyzed the archived data captured during China filed campaign in 1997. LRGOU recognized two possible inverted charged distribution thunderstorms. "Inverted charge distribution" means the lower positive charge and upper negative charge distribution. LRGOU is preparing an article to a scientific journal.
LRGOU intends to conduct a filed campaign for winter thunderstorms from December 2001 through January 2002. One of the objectives is improvement of the broadband interferometer through observations.
Additionally Japan Meteorological Agency (hereinafter JMA) has equipped and been operating a national wide SAFIR network. LRGOU contributed to evaluate the system performance by the comparison SAFIR data with TRMM/LIS data. JMA SAFIR apparently is working well.
Work continues with Sharon Stanfill and Mark Weber on the FAA-supported Oceanic Convective Weather project. Collaboration with Erich Stocker at NASA GSFC has enabled the construction and implementation of filters for the TRMM PR and VIRS 3-year satellite archive for appropriate meteorological entities. These include all locations where 30 and 40 dBZ reflectivity thresholds are exceeded at 7 km altitude, the locations of all isolated warm precipitating clouds, and the locations of all mesoscale convective systems. Monthly global maps are now available for all three entities for the three year period 1997-2000. The 40 dBZ locations are almost exclusively continental, whereas 30 dBZ locations predominate both over land and in the oceanic ITCZ. Warm precipitating clouds are primarily an oceanic phenomena, but leave unanswered the underlying explanation: a land-ocean contrast in updraft strength or in the concentration of cloud condensation nuclei. The MCS locations are to be compared with mesoscale lightning locations by Schumann resonance methods from Rhode Island.
A new antenna for the measurement of the vertical electric field has been constructed in the woods in Rhode Island, following small scale deforestation by Vadim Mushtak. Consisting of five large ceramic insulator columns donated by the Boston Edison Company, this 7 meter stack will ultimately replace the 10 m antenna mast installed by Charles Polk in the late 1960s and still currently used. Mike Stewart of Thunderstorm Technology designed and constructed the analog electronics. The pie-in-the-sky goal is the implementation of DSP to achieve wide band reception from the Schumann resonance region into the slow tail region at ELF, and beyond the waveguide cutoff to the sferics region at VLF. The DSP is being implemented by graduate student David Lowenfels.
The physical origin of the huge land-ocean lightning contrast has been examined by focussing on island electrification. Islands are miniature continents with a range of areas from <1 km2 to 106 km2. Predictions for critical island area for substantial thermal perturbation and for aerosol perturbation differ by an order of magnitude. Work is underway by graduate student Twiggy Chan with the Lightning Imaging Sensor data from the NASA TRMM (Tropical Rainfall Measuring Mission) satellite to test these predictions. Preliminary results with thunderday data from about 50 islands (WMO, 1956) suggests a transitional behavior between ocean and continent at an island area of a few hundred square kilometers. This result is more consistent with the thermal hypothesis than the aerosol hypothesis.
The radar/aerosol/lightning study in Brazil concerned with contrasting electrification in different meteorological regimes has been accepted for publication in the LBA Special Issue of the Journal of Geophysical Research. Major improvements in the paper were made possible by regime comparisons of the lightning stroke yield per kilogram of rainfall, made possible by Dave Wolffs TOGA radar analysis at GSFC and Rich Blakeslees analysis at MSFC with the Brazil lightning detection network.
Earle Williams has completed a review article on sprites for Physics Today to appear in the November issue. Sprite imagery that Physics Today editors chose to include was contributed by Matt Heavner, Walt Lyons, Dana Moudry, Dave Sentman, Mark Stanley, Mike Taylor, and Gene Wescott. Robert Golka provided considerable assistance with the work on glow discharge tubes.
On Oct. 4 the Standards Council of the National Fire Protection Assn. (NFPA) voted to retain NFPA-780 (the de factor lightning protection standard in the USA) at a meeting in Santa Fe NM NLSI, the DOE, the US military services, university researchers and Franklin commercial interests unified to advocate retention of 780 despite heavy opposition from Early Streamer Emission air terminal proponents. The version 2000 of NFPA-780 is to be released soon.
The ICOLSE meeting was about 40% under-attended due to the World Trade Center crisis. NLSI papers were on Safety for Small Shelters (with Vlad Rakov) and on NFPA-780. Both papers are on the NLSI WWW site at: www.lightningsafety.com
Recent NLSI consulting has focused on lightning hazard mitigation for explosives storage facilities. Site recommendations were completed at:
Hanscomb Air Force Base, MA Police HE Storage facility.
Hawthorne Army Depot, NV, HE storage facilities.
Los Alamos Natl Labs, NM, HE storage facilities.
NLSI has been appointed to the task force to revise Underwriters Laboratories UL-96, "Standard for Safety, Lightning Protection Components."
The City of Boulder CO recently completed a comprehensive review of athletic fields and swimming pools for lightning safety. Policies and site signage were developed under NLSI guidance.
The NLSI High Altitude Lightning Observation Station (HALOS) five year air terminal experiment was re-designed. Initially steel Franklin rods were installed but their high melting temperature made recognition of arcing and pitting difficult. Aluminum rods are now installed with thanks for continuing suggestions and help from Charles Moore, New Mexico Tech. The NLSI WWW site has photos of this modification and other details.
Don MacGorman and Dave Rust have continued analyses of data from STEPS. Recently they finished initial documentation of possible inverted-polarity electrical structures in STEPS thunderstorms. Evidence that such structures may exist were found in electric field profiles from seven storms. This was initially reported at the AGU annual fall meeting in December 2000 and is the subject of a paper that Rust and MacGorman recently submitted to Geophysical Research Letters. Other on-going analyses include collaborative studies with several STEPS investigators.
On July 3, 2001, fire destroyed the leased building known as the "Balloon Barn," used by the NSSL Field Observing Facilities and Support Group led by Dave Rust. The fire also destroyed all the equipment inside, valued at $2 million and owned by the National Severe Storms Laboratory, the University of Oklahoma, Texas A&M University, and Texas Tech University. The equipment included vehicles, mobile ballooning facilities, electric field meters for in situ balloon flights, and the components of a lightning mapping array which was to have been installed a few weeks later. Just seven weeks after the fire, NSSL's parent organizations, the Office of Oceanic and Atmospheric Research and the National Oceanic and Atmospheric Administration, provided nearly $1.2 million to replace what was lost by NSSL. The University of Oklahoma will replace its equipment by a combination of funds from insurance, the State of Oklahoma, and the University. All affected organizations are committed to a full replacement of facilities and capabilities. Details about the fire and recovery efforts are available at: http://www.nssl.noaa.gov/headlines/fire.html.
James Dye, Eric Defer (USRA), and Wiebke Deierling, a student from the Univ. of Hannover, Germany, have been involved in the Airborne Field Mill (ABFM) project which took place over Kennedy Space Center Florida during June 2000, Feb. 2001, and June 2001. The purpose of the campaigns were to obtain simultaneous in-situ airborne measurements of the electric fields and microphysical content in anvils and thick clouds near Kennedy Space Center using the Univ. of North Dakota Citation jet aircraft. The aircraft was instrumented with 6 field mills designed and built by Nasa Marshall Space Flight Center (MSFC) and an extensive array of microphysical probes to sample from a few microns to several millimeter sized particles including the new SPEC Cloud Particle Imager and the High Volume Sample Probe. The aircraft measurements were made in coordination with radar measurements from the Patrick Air Force Base 74-C radar and the Melborne NEXRAD radar. Measurements from the KSC LDAR and Cloud-to-Ground Lightning Sensing System, and surface electric field mill network provide information on lightning and surface electric fields. In particular, we want to determine decay rates of electric fields after lightning has occurred in the parent storm within the anvils over KSC. We also want to compare these decay rates with theoretically predicted decay rates. Although there was interest in seeing under what circumstances thick clouds (stratiform-type clouds deeper than 4500 feet thick residing between the 0 and 20 C levels) are electrified, there were too few cases during the February campaign to examine this question. This is a joint effort between NCAR, NASA MSFC, the Univ. of North Dakota, Univ. of Arizona, NOAA ETL, NOAA Hurricane Research Division and Kennedy Space Center.
Penetrations in a given storm initially were flown near to, but at a safe distance from, the convective cores of storms. Then subsequent passes were made in the anvil at different distances downstream to examine the decay of the electric field both with time and distance. As there currently is relatively limited information available on the vertical distribution of electric fields combined with microphysics, spiral ascents and descents were made when Air Traffic Control was able to give clearance.
Analysis of this data set is currently underway. Early results suggest that when the reflectivities in the anvils get low, approximately below 10 to 15 dBZ, the electric fields have decayed to a few kV/m or less. This and other comparisons with vertical reflectivity structure suggest that much of the charge in the anvils may be carried by precipitation-sized particles which can sediment out of the anvil, but this hypothesis needs much more testing. Early results also suggest that a radar based rule might be useful for indicating when there is little hazard from natural or triggered lightning in anvils.
Eric and Wiebke have also been examining both the 3D and 2D real-time ONERA lightning interferometer measurements collected during the STERAO experiment from NE Colorado in 1996. They are examining the structure of single flashes as well as flash characteristics over the entire lifetime of thunderstorms. The 3D system has 23 microsec time resolution and can store up to 4000 VHF sources per sec, while the 2D system has 100 microsec resolution and can store only 100 sources per sec. A comparison of the two systems shows that the flash detection efficiency of the 2D system is considerably lower than that from the 3D system. Averaged over the 5 hour lifetime of the 10 July 1996 STERAO storm, the 2D system detected about 55% of those detected with the 3D system by a detailed flash by flash analysis. The analysis also showed that determinations of flash duration from the 2D system were highly unreliable and that most flashes < 1 millisec duration as sensed by the 3D system are missed by the 2D system.
Robert Black (Robert.A.Black @ noaa.gov) reports :
This season, a fifth field mill was added to the NOAA WP-3D aircraft. This aircraft obtained our first 3-D electric field measurements in 3 Atlantic hurricanes and several cumuli off the SW coast of Florida during flights made in support of the CAMEX-IV experiment. Analysis of these data have not yet begun.
The Atmospheric Environment Research Unit at ONERA (Pierre.Laroche @ onera.fr) continues the development of the modeling of the sweeping of a lightning channel on an aircraft fuselage. Alain Delannoy (Alain.Delannoy @ onera.fr) and Philippe Lalande (Philippe.Lalande @ onera.fr) in collaboration with Anders Larson (andlar @ eagle.foi.se, now at F.O.I in Sweden) set up a physical model of this phenomenon which is presently under evaluation on a airliner numerical meshing.
The work on FORTE results, with the help of Abe Jacobsons group at Los Alamos, was used to specify the ORAGES microsatellite project mission which might be decided by the French Space Agency in 2002. ORAGES is a low orbiting mission project dedicated to the detection and localization of VHF emission from lightning. A preliminary prototype of ORAGES payload was tested this fall on a balloon at the CNESstratospheric balloon facility in South West of France.
ONERA has followed on the collaboration with INRS and Hydro-Quebec from Canada on triggering and guiding long arcs with a plasma channel created by an ultrashort laser pulse (H. Pepin et al, Physics of Plasmas, Vol.8 N°5, May 2001). The Canadian group led by Henri Pépin and Hubert Mercure has demonstrated that the plasma channel created by focusing the laser beam close to a positive electrode in a large air gap (3 to 7 m) can lower the inception voltage by 50% and increase the leader velocity by a factor of 10. A. Bondiou-Clergerie (Anne.Bondiou-Clergerie @ onera.fr ) and Philippe Lalande have obtained very encouraging results in modeling this effect, with the help of PhD. student Daniel Comtois, and François Vidal, in charge of theoretical aspects at INRS, who has brought new insights in the physics of the leader head.
The atmospheric electricity research group at the Institute of Geophysics reports:
The thundercloud dynamic structure and its space and time evolution depicted on the radar pictures, and simultaneous monitoring of the thunderstorm electrical activity by using the field mill and the Maxwell current density measurements at the earths surface are examined for the cases of thunderstorm days in Warsaw (P. Baranski: baranski @ igf.edu.pl). It is observed that distinct differences between spring and summer conditions for thundercloud development result in generation of different types of lightning discharge clusters. To obtain more information about lightning discharge characteristics, a flat plate antenna with the charge integrator and the 40 ns sampling A/D PC card with external triggering and 64 MB memory buffer on its board was used for recording the electric field changes of the observed lightning. The collected signatures for close ground flashes (less than 50 km distance from our measuring point) have shown an unusual behavior for some return stroke intervals. To explain those anomalies, extended investigations are planned with the use of data of the SAFIR detection and location network that is now installed in Poland.
The atmospheric electricity recordings are continued to be carried out on the background of meteorological, aerosol, radioactive and chemical pollution, and space charge density (the Obolensky method) observations at Swider Geophysical Observatory (M. Kubicki; swider @ igf.edu.pl). The results are being published and exchanged (M. Kubicki). The airborne radioactivity and electrical properties of ground level air are also studied (B. Laurikainen and M. Kubicki).
At the polar station at Hornsund, Spitsbergen, the electric field and vertical air-earth current recordings accompanied by the meteorological observations and geomagnetic, riometer and other geophysical measurements are continued (M. Kubicki and S. Michnowski).
New designs of electric field, air-earth and space charge density sensors are being developed (J. Berlinski, J. Drzewiecki, M. Kubicki).
The local effects at Hornsund and Swider on the electric field and air-earth current variations are analyzed (M. Kubicki, S. Warzecha). The influences of solar wind on the electrical variation at the ground during magnetic substorms in Hornsund are being examined (S. Michnowski, N. Kleimenova, S. Israelsson, N. Nikiforova, and M. Kubicki).
Andrew.Detwiler @ sdsmt.edu or John.Helsdon @ sdsmt.edu
The T-28 armored aircraft group at SDSMT continues to analyze data from the Severe Thunderstorm Electrification and Precipitation Study (STEPS). This effort includes Qixu Mo, Donna Kliche, Tom Warner, and Andy Detwiler. We are focusing so far on storms from two days during STEPS, 11 June and 29 June, and are working with other STEPS groups to analyze observations not only from the aircraft, but from the radars, lightning mapping array, balloon soundings, mobile mesonet, and other STEPS field observing systems. In addition, we are working with our colleagues John Helsdon and Dick Farley to compare observations with model simulations of these storms. We hope to develop analyses of several more interesting cases, as we look at the evolution of precipitation, electric charge distribution, and lightning in High Plains storms.
Graduate student Inna Sus, working with John Helsdon, has completed her Masters Thesis involving the development of a non-grid-point-dependent lightning parameterization scheme for the Institute of Atmospheric Sciences two- and three-dimensional storm electrification models (SEMs). The parameterization creates 50 m channel segments using random free electrons at the tip of each developing segment to determine the direction of each new segment. The scheme uses the electric field from the previous two segments to determine which of an altitude-dependent number of cosmic-ray-generated free electrons can create an avalanche within a minimum time. This electron is selected to determine the direction of the next segment. If two electrons meet the minimum time criterion, a branch segment is also created. Within the main charge regions, the gradient of the charge density is used to determine the next segment and/or branch direction. The parameterization creates realistic branched lightning channels without the restriction that they must propagate between model grid points.
Ph. D. candidate Xingjun Zhang, working with John Helsdon, is completing his dissertation research involving the use of the 3D SEM with a nine component and 18 reaction chemistry module along with the lightning parameterization of Helsdon et al. (1992) to simulate the NOx production by lightning and its subsequent distribution within the model cloud. The dissertation work has included 2D and 3D test calculations based on the 19 July 1981 CCOPE storm. The final part of the research work involves a simulation of the 10 July multiple cell case from the STERAO project. In the final simulation, three cells develop initially all electrically active. During the three hours of simulated time, two of the cells die out and the third takes on a supercell character. Overall, 1003 lightning discharges are generated and the resulting NOx distribution and its affect on O3 are being analyzed. The dissertation should be complete in December.
The VLF Group at STAR Laboratory of Stanford University is actively involved in experimental and theoretical work targeted at understanding the strong upward electrodynamic coupling of tropospheric thunderstorms to the mesospheric and lower ionospheric regions and associated optical and electromagnetic effects.
This past summer the VLF group, in conjunction with Torsten Neubert and Thomas Allin of the Danish Meteorological Institute, participated in an experiment to detect optical emissions from sprites in regions conjugate to their source locations. Rick Rairden of Lockheed Corporation was situated in France to provide telescopic imagery and sprite locations while Geoff Baimbridge of Stanford took photometer measurements of the night sky in South Africa. Unfortunately, due to weather limitations, no one to one correlations were made between sprites and conjugate flashes.
Elizabeth Gerken conducted telescopic (.72 x .90 degree field of view) optical measurements of heater-induced airglow created by the HAARP HF antenna array in Gakona, AK. Observing either the absence or presence of structure in the airglow would give additional insight into the atmospheric makeup of these heated regions. One might expect fine structure due to ambient electron density variations or small variations in the main lobe of the radiation pattern. In the past year two campaigns were conducted at HAARP, one in October 2000 and the other in March 2001. During the October campaign, the experiment was conducted on three nights and initial studies of the data do not show detectable airglow emissions. During the March campaign, artificial airglow at 630 nm was observed on two nights. On both nights airglow patches were produced above HAARP during O-mode pulses at the foF2 critical frequency.
Robert Moore and Geoff Baimbridge installed two new VLF receivers in Colorado in July to supplement the existing Holographic Array for Ionospheric Lightning research (HAIL). The new receivers will increase the accuracy at which the scattering pattern for early fast and lightning induced electron precipitation events can be resolved.
In August of 2001, Troy Wood of Stanford, in conjunction with Victor Pasko of Penn State University, acquired both broadband (100 Hz 25 kHz) and narrowband (NAU and NAA VLF transmitters) horizontal magnetic field measurements using two orthogonal loops antennas located in Vieques, Puerto Rico. The experiment obtained unique correlated measurements between the Arecibo Observatorys UHF and co-axial VHF radars, a VHF radio interferometer and the VLF broadband and narrowband data in order to study the atmosphere/ionosphere at unprecedented resolution.
Hurricane studies: we are using lightning locations from the National Lightning Detection Network to gain insight into the thermodynamics and dynamics of hurricanes. Our interest is not in electrification as such, but in the uses of remotely-sensed lightning as an indicator of convective activity. The NLDN has the huge benefit of being continuous in space and time, as long as the hurricanes of interest are over land or within about 400 km of the United States coast over water.
The question we address in our most recently submitted work is what factors determine the azimuthal distribution of convection in tropical cyclones. Convection is measured by ground flash density from the NLDN. All storms within range of the NLDN between 1985 and 1999 were included in the study. We have shown (Corbosiero and Molinari, "The Effects of Vertical Wind Shear on the Distribution of Convection in Tropical Cyclones", Monthly Weather Review, submitted) that vertical wind shear is the dominant influence. A downshear left maximum occurs within 100 km of the center of tropical cyclones (i.e., if vertical wind shear is from the west, maximum convection is in the northeast quadrant of the storm). A downshear right maximum occurs in the outer band region (r=100-300 km). The latter appears to represent the "stationary band complex" of Willoughby et al. (1984).
The downshear maximum was a robust signature: more than 90% of ground flashes occurred downshear in the storm core when vertical wind shear exceeded 5 m s-1. The results were equally valid over water and over land, and for depression, storm, and hurricane stages of the tropical cyclones.
Outgoing longwave radiation is a poor measure of convective intensity. Ground-based or airborne radar is only infrequently in range of hurricanes, and space-based radar (such as from TRMM) exists on polar orbiting satellites that only sporadically observe the tropical cyclone. We believe that lightning data provide a unique and beneficial perspective for this type of work.
NASA had delayed the launch of the space shuttle Columbia mission STS107 to late June 2002. Hence, the MEIDEX-Sprite campaign that will be conducted during the flight was pushed back to summer 2002. The campaign, managed by Yoav Yair, Zev Levin and Colin Price, involves observations of TLEs from space together with simultaneous global measurements of ELF/VLF waves from the parent lightning. This international cooperation now includes coordinated ground measurements from stations in Japan, Taiwan, Germany, USA and Israel. The primary science instrument is a Xybion IMC-201 multispectral camera with 6 filters. Data will be recorded digitally on board and as backup on the ground. Additional wide-field coverage by a color camera will be transmitted in real-time. The latest mission time-line allocates 10 shuttle orbits for dedicated sprite observations, with a total time of 250 minutes. Additional observations are being considered, as well as coordinated limb observations with the SOLSE instrument, also on-bord this flight. The MEIDEX payload is being integrated into the shuttle, after completing calibrations at NASAs Laboratory for Atmospheres at GSFC, and will be shipped to the cape in February 2002. The TAU group is developing operational forecast techniques to evaluate the regions of high convective activity, where major thunderstorms occur that will be conducive to sprite occurrence (http://luna.tau.ac.il/~tomer/MEIDEX/home.htm).
During the academic year 2001/2002 Colin Price is spending a sabbatical at the Meteorological Services of Canada in Toronto, Canada. He is working with Bill Burrows and Pat King using lightning data to improve the short-term forecasts of severe weather in Canada. They are using the Canadian Lightning Detection Network (CLDN), in operation since 1998, to investigate a number of case studies involving summer and winter lightning and severe weather. The lightning data will be compared to both satellite cloud data and ground-based radar to investigate the relationships between lightning activity and predictable model parameters.
Colin Price and student Mustafa Asfur continue studying the use of the Schumann Resonances for studying the earths climate. We have found a striking agreement betweeen lightning activity over Africa and South America and the amount of upper tropospheric water vapor in these regions.
Physics Ph.D. candidate Lee Coleman, under the direction of Tom Marshall, continues the analyses of balloon sounding, radar, and lightning data from SEET (Study of Electrical Evolution in Thunderstorms), a field project at Langmuir Lab in 1999. These analyses are being done in collaboration with Maribeth Stolzenburg and numerous colleagues at New Mexico Tech, including Paul Krehbiel, Bill Winn, Ron Thomas, and Bill Rison.
A total of 23 lightning flashes were initiated from July 13 to September 5, 2001, at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. Of these 23, 11 contained downward leader/upward return stroke sequences, and 12 were composed of the initial stage only. All triggered flashes effectively transported negative charge to ground. Fourteen flashes were triggered using an underground rocket-launching facility surrounded by a 70 x 70 m2 buried metallic grid, and nine flashes were triggered using the tower rocket launcher.
Rafael Sutil defended his Masters thesis titled "EMTP modeling of direct lightning strikes to the lightning protective system of a residential building". His current E-mail address is sutilrr @ bv.com.
Megumu Miki (Central Research Institute of Electric Power Industry, Tokyo, Japan), Vladimir A. Rakov, Keith J. Rambo, George H. Schnetzer, and Martin A. Uman authored a paper, submitted to JGR, titled "Electric Fields Near Triggered Lightning Channels Measured with Pockels Sensors". The electric fields in the immediate vicinity of triggered lightning channel were measured with Pockels sensors at the ICLRT. Electric field waveforms produced by leader/return stroke sequences at horizontal distances from the channel attachment point ranging from 0.1 to 1.6 m were obtained. Vertical electric field pulse peaks are in the range from 176 kV/m to 1.5 MV/m (the median is 577 kV/m), and horizontal electric field pulse peaks are in the range from 495 kV/m to 1.2 MV/m (the median is 821 kV/m). Additionally, vertical electric fields due to M components were measured and compared to electric fields produced by leader/return stroke sequences. The vertical electric field measured very close to the lightning channel tends to increase with an increase in the previous no-current interval, that is, in the time elapsed from the cessation of current of the preceding stroke (or of the initial-stage current).
Vladimir A. Rakov authored a paper titled "Transient Response of a Tall Object to Lightning". Experimental data showing the transient behavior of tall objects struck by lightning are reviewed. The influence of this transient behavior, illustrated by simple calculations, on measured lightning current and measured remote electromagnetic fields is discussed. The similarity of the statistical distributions of subsequent-return-stroke peak currents in (1) natural downward lightning, (2) natural upward (object-initiated) lightning, and (3) rocket-triggered lightning measured at objects with heights ranging from 4.5 to 540 m suggests that current peaks are not significantly influenced by the presence of a tall object, provided that measurements are taken at the top of the object. The peak current measured at the bottom of a tall object is usually more strongly influenced by the transient process in the object than the peak current at the top. Observations and modeling suggest that a tall metallic strike object replacing the lower part of lightning channel serves to enhance the lightning-radiated electromagnetic fields relative to the fields due to similar lightning discharges attached directly to ground, this effect being more pronounced for the sharper lightning current pulses. The paper is accepted for publication in the IEEE Trans. on Electromagnetic Compatibility.
Dr R.G.Harrison, Department of Meteorology, The University of Reading, P.O Box 243, Earley Gate, Reading Berks RG6 6BB UK. Email: r.g.harrison @ reading.ac.uk.
Work on fair weather electrification continues in the Department of Meteorology, at the University of Reading, UK. This has included new instrumentation for ion and aerosol charge measurements, both at the surface and aloft using balloons. Another important aspect has been the European CLOUD project assessing effects of cosmic ray ionisation on climate.
Giles Harrison contributed to the Workshop on Ion-Aerosol-Cloud Interactions (http://cloud.web.cern.ch/cloud/iaci_workshop/index.html) at CERN, discussing atmospheric electrical effects on cloud microphysics. The theoretical work of Fangqun Yu and Rich Turco (e.g. J.Geophys Res, 106, D5, pp4797-4814, 2001) on ultrafine aerosol formation from atmospheric ions opens new areas of application of fair weather atmospheric electricity. Linking non-thunderstorm atmospheric electricity with climate and cloud problems is of particular interest. This has motivated preliminary observations of free tropospheric aerosol and ion charges, undertaken on balloons carrying a modified radiosonde telemetry system. Using a new charge sensor making measurements at high vertical resolution, charged layers of aerosol can be detected under fair weather conditions.
Karen Aplin has published work on her new instrumentation for surface ion measurements, using the programmable ion mobility spectrometer. The combination of its two classical operating modes (voltage decay and ion current measurement) in one instrument allows self-calibration. A stable non-resistive 500fA current reference has also been developed for additional field calibration. The programmable ion mobility spectrometer (PIMS) will be deployed for further surface measurements of aerosols, charge and ionisation, but an airborne device is being planned to compliment the other radiosonde electrical measurements.
Related recent publications are listed in the publication section of this issue, and others are listed at http://www.met.rdg.ac.uk/~swshargi/.