Comparison of field, laboratory, and theoretical estimates of global nitrogen fixation by lightning

The various theoretical, laboratory, and field estimates reported in the literature for global nitrogen fixation by lightning have been calculated by using different lightning frequency values, channel lengths, and energy values. We have recalculated each of the individual estimates by using values of 7 km for channel length, two equivalent return strokes per lightning flash, and 100 flashes per second for global frequency, and a lightning energy input of 5×109 per flash. The adjusted mean value is 72.2±96.2 Tg N yr−1 for the theoretical category, 19.1±10.0 Tg N yr−1 for the laboratory category, and 152±59.9 Tg N yr−1 for the field category. Each of the three category adjusted mean NOx global production rates is larger than previously reported contributions to the global N budget, making lightning potentially the single largest source.