These lightning strokes usually reported by networks represent the individual pulses of strong current which occur during a complete lightning discharge. The complete discharge is referred to as a lightning flash. Strokes from the same flash occur within half a second of each other (usually considerably shorter). This is why a lightning flash appears to flicker to an observer. Many strokes of the same flash follow the same path, but some form a new one within a few kilometres. Whilst some flashes only contain a single stroke, most comprise of two or three, although occasionally flashes may contain more than ten! This, combined with the location uncertainty of the network can show multiple nearby points on their lightning map at the same time for what was actually produced by the same lightning flash.
Since the BTD-300 reports the location of the flash, i.e. the complete discharge and not the individual components, it may appear to count less lightning than a network reporting lightning strokes, which have not been grouped into flashes by the supplier. From a thunderstorm warning perspective, there is no advantage to reporting strokes compared to flashes (networks usually only do so since it is the fundamental unit derived from the radio pulses they detect). It is lightning flash rates (not strokes) that normally define a storm’s overall electrical activity and these will be the same as that identified by a human observer.
If you are concerned that a correctly sited and calibrated BTD-300 is not detecting sufficient nearby (within 30 NM/56 km) flashes in your area, you could try decreasing the lightning ratio threshold from the default (level 5). If you are concerned more with improving detection of the most distant (30-45 NM / 56-83 km) flashes detectable by the BTD-300, you could try lowering the lightning strength threshold from the default (level 5). It is important to be aware however that lowering any threshold from the default (level 5) setting has the potential to increase false alarms. If in doubt, please contact Biral for advice on the most suitable sensitivity levels for your requirements.
The BTD-300 is programmed with knowledge of the typical lightning strengths found throughout the world. However, there will be cases where a thunderstorm produces some extremely weak or strong lightning flashes which may be incorrectly ranged as being too far (weak flashes) or close (strong flashes). Even for these extreme events the deviation from the actual distance is usually small compared to other standalone lighting detectors, due to the unique operating principle of the BTD-300.
It is worth noting that the diversity of radio signal amplitudes produced by different lightning strokes means that a signal from lightning 1000 km away can have the same strength as a stroke only 30 km away! The same does not apply to its quasi-electrostatic signal used by the BTD-300, which therefore provides a substantially more reliable measure of lightning range than by using radio signal amplitude alone. Nonetheless, radio signals are the only practical method of lightning direction finding available for single site systems, so the direction finder module used by the BTD-300 must rely upon these signals.
Since the top of the snow represents the ground plane, the effective height of the antennas will be reduced according to the snow depth around the base of the unit. This is not expected to significantly affect performance (principally detection of distant flashes) until the snow depth exceeds approximately 60 cm (2 ft). For persistent snow depths in excess of 60 cm the BTD-300 will tend to overestimate lightning distance, so will require re-calibration, and have a lower detection efficiency for far away (>20 NM / 37 km) flashes. Snow depths exceeding 140 cm (~4.5 ft) will likely make contact with the tertiary antenna and prevent the system from detecting lightning (although it will still detect charged precipitation and strong electric field variability), so the area immediately surrounding the BTD-300 will need clearing of snow. The optional electronics enclosure heater available for the BTD-300 upon initial order is recommended for installation in cold environments where the minimum ambient temperature is lower than -20°C (-4°F).
Although lightning is relatively uncommon during snowstorms, it does occur during certain meteorological conditions so there is still a risk to be considered. For example, winter rain/hail showers in mid-latitudes can produce extremely powerful cloud-to-ground lightning, although the storm’s lightning flash rate is usually low compared to summer thunderstorms. Such winter storms tend to produce highly charged precipitation and strong electric fields, allowing the BTD-300 to warn of their potential overhead development.