'What is EDOT?'Check out these data products available on-line:
'What is EDOT?'We use EDOT as shorthand for electric field change, the principle physical measurement we make in our ground-based lightning studies. The name 'EDOT' can actually be a little misleading, since it is 'fast E' that we measure (differential electric field on a millisecond time scale), rather than dE/dt as suggested by the EDOT moniker. We measure E using an instrument called an electric field change meter, which consists of a flat plate antenna backed by a charge amplifier and line driver. Our field change meters are sensitive to a bandwidth that extends from approximately 300 Hz to 300 kHz, just below the commercial AM radio band. We digitize meter output with 12 bits at a sample rate of 1 Msample/sec. This high data rate precludes our recording of all data for all time, so we run our digitizers in a snapshot mode, recording data only when the input waveform exceeds a predetermined bipolar trigger threshold. When a meter triggers and records data, it also latches a UTC time stamp from a GPS clock, providing us with an absolute time tag for the recorded waveform. By utilizing multiple EDOT stations configured in arrays, we can use absolute waveform time tags to locate lightning strokes. We currently record both cloud-to-ground and intracloud lightning strokes from 11 EDOT stations. We operate five stations in a New Mexico/ West Texas array, five in a Florida array; and one in Nebraska.
'What is FORTE?'FORTE is a small satellite that was launched into low-Earth orbit on 29 August 1997 by a Pegasus booster. FORTE, which stands for Fast On-orbit Recording of Transient Events, was designed to test technologies to remotely monitor compliance with arms control treaties. FORTE's instruments detect, record, and analyze transient radio frequency and optical signals that arise from near the Earth's surface. A joint project between the Department of Energy's Los Alamos and Sandia national laboratories, the satellite is also providing a wealth of data on the physics of lightning and the ionosphere.
An advantage of the FORTE satellite-based lightning recorder is that
it provides us with a sampling of data from nearly the entire globe. However, at 7
km/s, it moves along at a pretty good clip and can provide only 15 minutes of observation
time over a single region on a single plass. Also, unless FORTE records events with
its optical imager, we do not know where recorded RF and optical photodiaode events
originate. Ground-based studies allow us to address these shortfalls to some extent,
but don't provide a panacea either. Our arrays (individually or used in conjunction
with one another as a very large array) provide 24 hr/day coverage over a limited
geographical region, in contrast to FORTE, which provides snapshot histories of regions
all over the globe. 
From the ground we can track
the development of a thunderstorm or thunderstorm system from its first sparks until it
dies out (as long as this all occurs within our coverage area). This ability gives
us information about temporal storm development. We are also able to geolocate
lightning strokes within the storm (with accuracies as good as a few km that get worse as
the storm moves further from the array), and can thus also monitor spatial storm
development. We fuse our spatiotemporal storm histories with data from other
meteorological assests, such as weather radars, to learn more about thunderstorms and
lightning. Also, because we monitor low frequency [300 Hz to 300 kHz] electric field
change from the ground (in contrast to FORTE, which records very high frequency [30 to 300
MHz] radiation), we sense different physical characteristics of lightning strokes and
learn more about the physics of lightning.