The Lightning Flash
number of flashes for low structure heights and overestimate the number of flashes
for high structure heights. Or, more probably, it may be that Eriksson's curve is for a
combination of flat and mountainous terrain.
However, since upward strokes occur for high structures, for heights above
about 100 meters this equation is not totally valid for the important negative downward
stroke. Eriksson then presented an equation for the number of upward strokes
in per unit of the total number of strokes N(G):