Quantification of lightning-produced NOx over the Pyrenees by using different TROPOMI-NO2 research products
Authors: Perez-Invernon Francisco Javier , Huntrieser Heidi , Erbertseder Thilo , Loyola Diego , Valks Pieter , Liu Song , Allen Dale , Pickering Kenneth , Bucsela Eric , Jöckel Patrick , van Greffen Jos , Eskes Henk , Soler Sergio , Gordillo-Vázquez Francisco J. 
Published: March 2021

&lt;p&gt;&lt;span&gt;&lt;span&gt;Lightning discharges are one of the main sources of atmospheric NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;, contributing about 10% of NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; emissions globally and playing an important role &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;for&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; the concentration of ozone and other chemical species in the upper troposphere. Lightning produces between 2-8 Tg N per year globally (100-400 mol NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; per flash).&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; R&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;educing the uncertainty &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;of&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; the NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x &lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;production by lightning and understanding the factors that influence this production is still a challenge. &lt;/span&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;span&gt;The TROPOspheric Monitoring Instrument (TROPOMI) is orbiting the Earth from a near-polar, sun-synchronous orbit since October 2017. TROPOMI is equipped with four spectrometers that provide information about the chemical composition of the troposphere with unprecedented horizontal spatial resolution&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;s&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; of &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;3.5 x 7 km before 6 August 2019 and &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;3.5 x 5.5 km &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;after that date&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;. In this work, we &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;combine&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; the DLR-NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; research product, &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;the&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; DLR cloud operational product &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;and &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;the &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;TROPOMI v2.1_test NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; product &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;to estimate the production of NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; per flash (LNO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;). The v2.1_test NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; product contains more useful data pixels than the official offline v1.x data product, because of better treatment o&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;f&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; saturation of the TROPOMI measurements (which occurs frequently over high bright clouds that are often linked with LNOx) and the use of an improved version of the FRESCO cloud algorithm. &lt;/span&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;span&gt;We for the first time ever use &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;these &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;chemical measurements from TROPOMI combined with lightning radio measurements provided by the EUropean Cooperation for LIghtning Detection (EUCLID) and the Earth Network Total Lightning Network (ENTLN), together with lightning optical measurements provided by the space-based Lightning Imaging Sensor (LIS) to estimate the Detection Effiency (DE) of EUCLID and ENTLN&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;. In addition, w&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;e use&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; the&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations to calculate the air mass factor employed to convert tropospheric slant column of measured NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; to vertical column LNO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x &lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;and the winds provided by reanalysis data to &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;eliminate&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; the influence of upwind storms in the &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;estimation of the &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;background &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;Concentration.&lt;/span&gt;&lt;/span&gt;&lt;span&gt; &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;span&gt;We focus our analysis &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;o&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;n different &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;remote &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;regions, where the background concentration of NO is relatively low. In particular, we focus our analysis on &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;11&lt;/span&gt;&lt;/span&gt;&lt;span&gt; &lt;/span&gt;&lt;span&gt;&lt;span&gt;thunderstorm &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;case&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;s&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; taking place near the Pyrenees&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;, where &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;intense&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; thunderstorms are frequent and the DE of EUCLID and ENTLN is relatively high and homogeneous. According to our preliminary results from a single case &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;using the DLR-NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; research product&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;, &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;we get about 400 mol NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; per flash when we estimate the background using NO&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&lt;span&gt;x&lt;/span&gt;&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt; from CARIBIC flights and about 200-600 mol per flash when we estimate the background using TROPOMI measurements from non-flashing pixels.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;