A Study of Boreal Mid-Latitude Lightning-NOx Production
Abstract
Lightning is the primary source of NOx (NO + NO2) in the mid-to-upper troposphere, where this species plays an important role in ozone and greenhouse-gas chemistry. To accurately characterize the global NOx budget and improve CTMs, the production efficiency (PE) of lightning NOx (LNOx) in moles per lightning flash must be known. We estimate the PE based on satellite data from the Ozone Monitoring Instrument (OMI) and the ground-based World-Wide Lightning Location Network (WWLLN). OMI NO2 data (NASA Standard Product v3.0) from June, July and August over mainly continental regions around Eastern North America, Europe and East Asia are compared with lightning counts from WWLLN. The WWLLN counts are calibrated against satellite observations to obtain an estimate of the WWLLN detection efficiency. The OMI v3.0 data consist of NO2 slant columns, cloud fraction and pressure, and a simple latitude-dependent NO2 stratosphere. Additional calculations using NO2 and NOx profiles from the Global Modeling Initiative (GMI) model are used to compute air mass factors for conversion of the NO2 measurements to moles LNOx in 1o longitude × 1o latitude grid boxes. WWLLN counts over a 1-hour period preceding OMI overpass are binned in the same boxes. We estimate an overall mean PE of 180 ± 100 moles LNOx produced per flash. However, the PE is observed to depend strongly on flash rate, with higher flash rates producing less LNOx per flash. Although not reported in previous satellite investigations, this finding is consistent with some aircraft and ground-based studies. The non-linear dependence is evident not only in the derived NOx amounts but in the initial OMI NO2 columns, themselves. It is most apparent over lower cloud tops and less so above storms with high anvils, where the PE becomes nearly constant. We discuss the implications of these findings.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A11O2506B
- 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