Lightning Location, NOx Production, and Transport by Anomalous and Normal Polarity Thunderstorms

Abstract

Production and transport of NO x by convection is critical as it serves as a precursor to tropospheric ozone, an important greenhouse gas. Lightning serves as the largest source of nitrogen oxides (NO x = NO + NO 2 ) to the upper troposphere (UT) and is one of the largest natural sources of NO x . Interest is placed on the vertical advection of NO x because its lifetime increases to several days in the UT compared to roughly 3 hr in the lower troposphere and boundary layer. Thus, lightning can play an important role in ozone production within the UT. However, the amount of NO x produced per flash and NO x advection in storms remain uncertain. This study investigates lightning NO x (LNO x ) production and transport processes in anomalous (midlevel positive charge) and normal polarity (midlevel negative charge) thunderstorms by advecting parcels containing LNO x from the flash channels of over 5,600 lightning flashes observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. Results reveal that most flash channels occur near 6-8 km in the normal polarity thunderstorms and 5-6 km within anomalous polarity thunderstorms. Larger flash rates and stronger updrafts in anomalous storms result in considerably larger LNO x mixing ratios (peaks of 0.75-1.75 ppb) in the UT compared to normal polarity storms (peaks < 0.5 ppb). A slightly lower mean flash LNO x production was also found among all five storms in this study (storm mean values of 72-158 moles per flash) compared to previous estimates, which generally parameterize LNO x by flash rate rather than flash count.

Observations of Lightning NOx Production From GOES‐R Post Launch Test Field Campaign Flights

“…Assuming the enhanced LNO x was distributed over the volume of the observed cloud and adjusting for uncertainties, they obtained a PE of 117-332 mol NO x flash −1 . Davis et al (2019) examined the PE for three anomalous and two normal polarity DC3 storms that occurred within the range of Lightning Mapping Arrays (LMAs). After assuming LNO x production was proportional to channel length and pressure, they obtained a PE of 61-158 mol per LMA flash.…”

“…A critical quantity needed to infer the global production is the mean number of moles of NO x produced per lightning flash. Recent estimates for this quantity vary by an order of magnitude with values between 50 and 700 mol per flash (Allen et al., 2019; Bucsela et al., 2019; Davis et al., 2019; Lapierre et al., 2020; Marais et al., 2018; Pickering et al., 2016; Pollack et al., 2016; Zhang et al., 2020). Of course, Lightning NO x production efficiency (LNO x PE) may also vary with the flash type (cloud‐to‐ground versus intracloud) and altitude adding additional uncertainty to the mix (Cummings et al., 2013; DeCaria et al., 2005; Fehr et al., 2004; Fuchs & Rutledge, 2018; Koshak et al., 2014; Mecikalski & Carey, 2018; Ott et al, 2010, 2007; Price et al., 1997).…”

Estimates of lightning NO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; production based on high-resolution OMI NO&lt;sub&gt;2&lt;/sub&gt; retrievals over the continental US

“…The tropospheric NO x background was removed by subtracting the temporal average of NO x at each box where the value was weighted by the number of OMI pixels which meet the optical cloud pressure and CRF criteria required to be considered deep convection but have one flash or fewer instead. The lofted pollution was considered to be 15 % of total NO x according to the estimation from DeCaria et al (2000DeCaria et al ( , 2005, and the average chemical delay was adjusted by 15 % following the 3 h LNO x lifetime in the nearby field of convection (Nault et al, 2017). However, there were negative LNO x values caused by the overestimation of the tropospheric background and stratospheric NO 2 at some locations.…”

Estimates of Lightning NO&lt;sub&gt;x&lt;/sub&gt; Production based on High Resolution OMI NO&lt;sub&gt;2&lt;/sub&gt; Retrievals over the Continental US

“…Because CP only represents the development of clouds, the vertical structure of flashes can not be derived from the CP values only. As discussed in several previous studies, flash channel length varies and depends on the environmental conditions(Carey et al, 2016;Mecikalski and Carey, 2017;Fuchs and Rutledge, 2018) Davis et al (2019). compared two kinds of flashes: normal flashes and anomalous flashes.…”