Direct satellite observation of lightning-produced NO<sub>x</sub>

Abstract

Abstract.Lightning is an important source of NO x in the free troposphere, especially in the tropics, with strong impact on ozone production. However, estimates of lightning NO x (LNO x ) production efficiency (LNO x per flash) are still quite uncertain.In this study we present a systematic analysis of NO 2 column densities from SCIAMACHY measurements over active thunderstorms, as detected by the World-Wide Lightning Location Network (WWLLN), where the WWLLN detection efficiency was estimated using the flash climatology of the satellite lightning sensors LIS/OTD. Only events with high lightning activity are considered, where corrected WWLLN flash rate densities inside the satellite pixel within the last hour are above 1 /km 2 /h. For typical SCIAMACHY ground pixels of 30 × 60 km 2 , this threshold corresponds to 1800 flashes over the last hour, which, for literature estimates of lightning NO x production, should result in clearly enhanced NO 2 column densities.From 2004-2008, we find 287 coincidences of SCIA-MACHY measurements and high WWLLN flash rate densities. For some of these events, a clear enhancement of column densities of NO 2 could be observed, indeed. But overall, the measured column densities are below the expected values by more than one order of magnitude, and in most of the cases, no enhanced NO 2 could be found at all.Our results are in contradiction to the currently accepted range of LNO x production per flash of 15 (2-40) × 10 25 molec/flash. This probably partly results from the specific conditions for the events under investigation, i.e. events of high lightning activity in the morning (local time) and mostly (for 162 out of 287 events) over ocean.Within the detected coincidences, the highest NO 2 column densities were observed around the US Eastcoast. This might Correspondence to: S. Beirle (steffen.beirle@mpic.de) be partly due to interference with ground sources of NO x being uplifted by the convective systems. However, it could also indicate that flashes in this region are particularly productive.We conclude that current estimates of LNO x production might be biased high for two reasons. First, we observe a high variability of NO 2 for coincident lightning events. This high variability can easily cause a publication bias, since studies reporting on high NO x production have likely been published, while studies finding no or low amounts of NO x might have been rejected as errorneous or not significant. Second, many estimates of LNO x production in literature have been performed over the US, which is probably not representative for global lightning.

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

“…More than 80 % of summertime upper tropospheric NO x above the eastern United States is produced by lightning ) and can be a significant contributor to surface ozone (Hudman et al, 2009). Lightning NO x (NO 2 ) has been detected from space (Beirle et al, 2010;Choi et al, 2005). The lightning-produced NO perturbs atmospheric composition in several ways relevant to climate, as NO is an important determinant of OH / HO 2 ratios via Reaction (R3).…”

The NASA Lightning Nitrogen Oxides Model (LNOM): Application to air quality modeling

“…There has been considerable variability in the estimates of lightning NOx production per flash; see for example the summary table in Labrador et al (2005), the review paper by , and the studies by DeCaria et al (2000DeCaria et al ( , 2005, Beirle et al (2004Beirle et al ( , 2010, Langford et al (2004), Rahman et al (2007), Huntrieser et al (2008), Jourdain et al (2010), Ott et al (2010), and Peterson and Beasley (2011). The variability in these estimates is linked to the differences in the estimation methods employed, and the natural variability of lightning.…”

Cloud-resolving chemistry simulation of a Hector thunderstorm

“…The importance of investigating LNO 2 signals with satellite observations is to identify regional differences in thunderstorm contribution to NO 2 (Beirle et al, 2010). Here the NO 2 column analysis provides the NO 2 satellite retrieval community with potential outflow expectations for a highly electrified, high NO x producing storm.…”