Lightning NOxProduction in the Tropics as Determined Using OMI NO2Retrievals and WWLLN Stroke Data

Nitrogen oxide (NOx) production by lightning in the tropics is estimated using tropospheric NOxamounts (LNOx*) over deep convective grid boxes derived from Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO2) slant columns and detection‐efficiency–adjusted World Wide Lightning Location Network (WWLLN) flashes. The lightning NOxproduction efficiency (LNOxPE) in the tropics is determined for the austral and boreal summers of 2007 to 2011 by regressing regional mean daily values of LNOx* for individual seasons against daily flash totals during flash windows prior to the OMI overpass. LNOxPE is determined to be approximately two times larger over marine locations than over continental locations possibly because marine flashes are more energetic. Overall, the mean LNOxPE for the tropics is calculated to be 170 ± 100 mol per flash with values over the tropical Pacific (low flash rate region) being largest. The main contributors to uncertainties in PE are uncertainties in WWLLN flash detection efficiency, upper tropospheric NOxlifetime in the near field of convection, and air mass factor biases. The high temperatures associated with lightning break apart the bonds of molecular nitrogen and oxygen leading to the production of nitrogen oxides (NOx) and subsequent increases in the concentrations of ozone (O3) and the hydroxyl radical (OH) and subsequent decreases in the concentrations of methane (CH4), thus impacting the climate system. The magnitude of NOxproduction by lightning is inferred over the tropics using nitrogen dioxide (NO2) columns from the Ozone Monitoring Instrument (OMI) aboard the NASA Aura spacecraft and lightning stroke data from the ground‐based World Wide Lightning Location Network (WWLLN). Overall, it was found that, on average, each lightning flash produces 170 mol of NOxwith an uncertainty of approximately 60%. This value is within the commonly cited range of 100 to 400 mol per flash. In addition, it was found that flashes at tropical marine locations produce approximately two times as much NOxper flash as flashes at tropical continental locations and that NOxproduction per flash is greater in regions with low flash rates than in regions with high flash rates. Mean NOxproduction by lightning in the tropics is in the range of 70 to 270 mol per flash.Mean NOxproduction per flash at tropical marine locations is approximately twice as large as at tropical continental locations.When averaged regionally within the tropics, NOxproduction per flash is smaller for high flash rates than low flash rates.