Lightning NOxProduction in the Tropics as Determined Using OMI NO2Retrievals and WWLLN Stroke data
Abstract
Deep convective clouds affect atmospheric chemistry in a variety of ways. Lightning produces nitric oxide (NO), which quickly comes into equilibrium with NO2 in the atmosphere. However, global production of NOx (NO + NO2) from lightning is uncertain by a factor of four. NOx production by lightning in the tropics is estimated using Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO2) slant columns and detection-efficiency adjusted World Wide Lightning Location Network (WWLLN) flashes during the boreal summers of 2007 to 2011. OMI NO2 slant columns are converted to vertical columns of tropospheric NOx (VLNOx*), which are then converted to vertical columns of tropospheric NOx due to recent lightning (VLNOx) by subtraction of a tropospheric background that is given by the mean VLNOx*at the same locations on non-flashing days. Estimates of LNOx PE for the tropical Americas, tropical Africa, tropical Pacific, the Gulf of Mexico region, and the combined tropics are obtained using two approaches. In the summation approach, mean VLNOx over flashing grid boxes is divided by mean flashes during a flash window prior to the time of the OMI overpass. In the regression approach, mean daily VLNOx*values over a region are regressed against mean daily flashes during the flash window. LNOx PE is determined to be approximately three times larger over marine locations than over continental locations possibly because marine flashes are more energetic. Overall, the mean LNOx PE for the tropics is calculated to be 157 ± 72 moles per flash with values over the tropical Pacific (low flash rate region) being larger and values over tropical Africa (high flash rate region) being smaller. The main contributors to uncertainty are uncertainties in WWLLN detection efficiency and upper tropospheric NOx lifetime in the near field of convection.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A11O2507A
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSESDE: 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSESDE: 3314 Convective processes;
- ATMOSPHERIC PROCESSESDE: 3354 Precipitation;
- ATMOSPHERIC PROCESSES