Lightning Flash Length Estimation from Lightning Mapping Array Measurements

Lightning consists of bidirectional channels beginning at the initiation point and branching many times. One measure to compare two lightning flashes in the length of the channels. An effect of a storm on the atmospheric chemistry is chemical production in lightning channels. This effect should depend on the total channel lengths at different altitudes. Source locations from the Lightning Mapping Array (LMA) gives a picture of the channel development and branching. To get a channel length from the source locations, the sources need to be joined into the channels. There is not enough information to do this in a unique manner so any channels are an approximation. We have developed an algorithm to join the the sources and are refining it. Not all the sources are detected and located so the length estimate will be an underestimate. The channel length from joining the sources seems to be sensitive to array sensitivity and noise. In an effort to estimate the channel length in a more robust manner we have a developed a method similar to flash extent density. It is based on the number of cells in a x-y projection of the lightning that are occupied by at least one detected source. A good length estimate is the number of cells times the length of a side of the cell. This estimate depends on cell size and a good cell size maximizes the estimate.