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A cloud‐resolved storm and chemistry simulation of a severe convective system in Oklahoma constrained by anvil aircraft observations of NOxwas used to estimate the mean production of NOxper flash in this storm. An upward ice flux scheme was used to parameterize flash rates in the model. Model lightning was also constrained by observed lightning flash types and the altitude distribution of flash channel segments. The best estimate of mean NOxproduction by lightning in this storm was 80–110 mol per flash, which is smaller than many other literature estimates. This result is likely due to the storm having been a high flash rate event in which flash extents were relatively small. Over the evolution of this storm a moderate negative correlation was found between the total flash rate and flash extent and energy per flash. A longer‐term simulation at 36‐km horizontal resolution with parameterized convection was used to simulate the downwind transport and chemistry of the anvil outflow from the same storm. Convective transport of low‐ozone air from the boundary layer decreased ozone in the anvil outflow by up to 20–40 ppbv compared with the initial conditions, which contained stratospheric influence. Photochemical ozone production in the lightning‐NOxenhanced convective plume proceeded at a rate of 10–11 ppbv per day in the 9–11 km outflow layer over the 24‐hr period of downwind transport to the Southern Appalachians. Photochemical production plays a large role in the restoration of upper tropospheric ozone following deep convection. Nitrogen oxides are important precursors for tropospheric ozone, an important greenhouse gas. The global amount of nitrogen oxides produced by lightning remains highly uncertain, primarily because of uncertainty in the amount produced per flash. In this paper we use an approach that involves cloud‐resolved modeling with chemistry, constrained by observed flash rates and aircraft measurements of nitrogen oxides, to make an estimate of the mean production per flash for an observed severe storm over Oklahoma. We estimate that the mean production rate was 80–110 mol per flash for this high flash rate storm, which is at the lower end of the range reported in the literature. We use a regional model to follow the outflow of the Oklahoma storm downwind to estimate the amount of ozone produced in the upper tropospheric outflow plume by the lightning‐generated nitrogen oxides. Our estimate is in the range found in previous studies, and we note that the ozone production by photochemistry is an important process in restoring upper tropospheric ozone following storms that lofted low values of ozone from the layer of air near the surface. Mean lightning NOxproduction was 80–110 mol flash−1for a high flash rate storm, based on a model constrained by flash and NOxobservationsNet O3production in the upper outflow of a high flash rate storm was at a rate of 10–11 ppbv day−1during 24 hr of downwind transportProduction of O3due to lightning NOxcontributed to the recovery of upper tropospheric O3following reductions due to convective transport Mean lightning NOxproduction was 80–110 mol flash−1for a high flash rate storm, based on a model constrained by flash and NOxobservations Net O3production in the upper outflow of a high flash rate storm was at a rate of 10–11 ppbv day−1during 24 hr of downwind transport Production of O3due to lightning NOxcontributed to the recovery of upper tropospheric O3following reductions due to convective transport

ABSTRACTUsing the Community Multiscale Air Quality (CMAQ) model and the Benefits Mapping and Analysis Program – Community Edition (BenMAP-CE) tool, we estimate the benefits of anthropogenic emission reductions between 2002 and 2011 in the Eastern United States (US) with respect to surface ozone concentrations and ozone-related health and economic impacts, during a month of extreme heat, July 2011. Based on CMAQ simulations using emissions appropriate for 2002 and 2011, we estimate that emission reductions since 2002 likely prevented 10– 15 ozone exceedance days (using the 2011 maximum 8-hr average ozone standard of 75 ppbv) throughout the Ohio River Valley and 5– 10 ozone exceedance days throughout the Washington, DC – Baltimore, MD metropolitan area during this extremely hot month. CMAQ results were fed into the BenMAP-CE tool to determine the health and health-related economic benefits of anthropogenic emission reductions between 2002 and 2011. We estimate that the concomitant health benefits from the ozone reductions were significant for this anomalous month: 160–800 mortalities (95% confidence interval (CI): 70–1,010) were avoided in July 2011 in the Eastern U.S, saving an estimated $1.3–$6.6 billion (CI: $174 million–$15.5 billion). Additionally, we estimate that emission reductions resulted in 950 (CI: 90–2,350) less hospital admissions from respiratory symptoms, 370 (CI: 180–580) less hospital admissions for pneumonia, 570 (CI: 0–1650) less Emergency Room (ER) visits from asthma symptoms, 922,020 (CI: 469,960–1,370,050) less minor restricted activity days (MRADs), and 430,240 (CI: −280,350–963,190) less symptoms of asthma exacerbation during July 2011.Implications: We estimate the benefits of air pollution emission reductions on surface ozone concentrations and ozone-related impacts on human health and the economy between 2002 and 2011 during an extremely hot month, July 2011, in the eastern United States (US) using the CMAQ and BenMAP-CE models. Results suggest that, during July 2011, emission reductions prevented 10-15 ozone exceedance days in the Ohio River Valley and 5-10 ozone exceedance days in the Mid Atlantic; saved 160-800 lives in the Eastern US, saving $1.3 - $6.5 billion; and resulted in 950 less hospital admissions for respiratory symptoms, 370 less hospital admissions for pneumonia, 570 less Emergency Room visits for asthma symptoms, 922,020 less minor restricted activity days, and 430,240 less symptoms of asthma exacerbation.

Oxides of nitrogen are critical trace gases in the troposphere and are precursors for nitrate aerosol and ozone, which is an important pollutant and greenhouse gas. Lightning is the major source of NOx(NO + NO2) in the middle to upper troposphere. We estimate the production efficiency (PE) of lightning NOx(LNOx) using satellite data from the Ozone Monitoring Instrument and the ground‐based World Wide Lightning Location Network in three northern midlatitudes, primarily continental regions that include much of North America, Europe, and East Asia. Data were obtained over five boreal summers, 2007–2011, and comprise the largest number of midlatitude convective events to date for estimating the LNOxPE with satellite NO2and ground‐based lightning measurements. In contrast to some previous studies, the algorithm assumes no minimum flash‐rate threshold and estimates freshly produced LNOxby subtracting a background of aged NOxestimated from the Ozone Monitoring Instrument data set itself. We infer an average value of 180 ± 100 moles LNOxproduced per lightning flash. We also show evidence of a dependence of PE on lightning flash rate and find an approximate empirical power function relating moles LNOxto flashes. PE decreases by an order of magnitude for a 2 orders of magnitude increase in flash rate. This phenomenon has not been reported in previous satellite LNOxstudies but is consistent with ground‐based observations suggesting an inverse relationship between flash rate and size. Oxides of nitrogen (NOx= NO + NO2) are minor gases in the atmosphere but are important in its chemistry. Their major source in the upper troposphere is lightning, which creates nitric oxide (NO) by breaking apart nitrogen and oxygen molecules. Estimating how much total NO is produced requires knowledge of the average production efficiency of individual lightning flashes. From midlatitude satellite measurements of nitrogen dioxide (NO2) and lightning detections from ground, we find a mean production efficiency of 180 moles NO per lightning flash, somewhat smaller than the ~250 mol/fl averaged globally in previous studies. We also show that production efficiency is smaller in storms with more frequent lightning. Lightning flash rates from the World Wide Lightning Location Network are distinctly correlated with lightning‐NOxestimates from the Ozone Monitoring InstrumentThe observations yield a mean midlatitude production efficiency (PE) of 180 ± 100 moles of lightning NOx(LNOx) per lightning flashLNOxproduction is proportional to a power function of lightning flash rate, with exponent between 0 and 1. Results imply that the PE is lower in storms with more frequent flashes

Nitrogen oxide (NOx) production by lightning in the tropics is estimated using tropospheric NOxamounts (LNOx*) over deep convective grid boxes derived from Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO2) slant columns and detection‐efficiency–adjusted World Wide Lightning Location Network (WWLLN) flashes. The lightning NOxproduction efficiency (LNOxPE) in the tropics is determined for the austral and boreal summers of 2007 to 2011 by regressing regional mean daily values of LNOx* for individual seasons against daily flash totals during flash windows prior to the OMI overpass. LNOxPE is determined to be approximately two times larger over marine locations than over continental locations possibly because marine flashes are more energetic. Overall, the mean LNOxPE for the tropics is calculated to be 170 ± 100 mol per flash with values over the tropical Pacific (low flash rate region) being largest. The main contributors to uncertainties in PE are uncertainties in WWLLN flash detection efficiency, upper tropospheric NOxlifetime in the near field of convection, and air mass factor biases. The high temperatures associated with lightning break apart the bonds of molecular nitrogen and oxygen leading to the production of nitrogen oxides (NOx) and subsequent increases in the concentrations of ozone (O3) and the hydroxyl radical (OH) and subsequent decreases in the concentrations of methane (CH4), thus impacting the climate system. The magnitude of NOxproduction by lightning is inferred over the tropics using nitrogen dioxide (NO2) columns from the Ozone Monitoring Instrument (OMI) aboard the NASA Aura spacecraft and lightning stroke data from the ground‐based World Wide Lightning Location Network (WWLLN). Overall, it was found that, on average, each lightning flash produces 170 mol of NOxwith an uncertainty of approximately 60%. This value is within the commonly cited range of 100 to 400 mol per flash. In addition, it was found that flashes at tropical marine locations produce approximately two times as much NOxper flash as flashes at tropical continental locations and that NOxproduction per flash is greater in regions with low flash rates than in regions with high flash rates. Mean NOxproduction by lightning in the tropics is in the range of 70 to 270 mol per flash.Mean NOxproduction per flash at tropical marine locations is approximately twice as large as at tropical continental locations.When averaged regionally within the tropics, NOxproduction per flash is smaller for high flash rates than low flash rates.

Deep convective transport of gaseous precursors to ozone (O3) and aerosols to the upper troposphere is affected by liquid phase and mixed‐phase scavenging, entrainment of free tropospheric air and aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high‐resolution (dx≤3 km) WRF‐Chem simulations of a severe storm, an air mass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH2O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF‐Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH2O, methyl hydroperoxide (CH3OOH), and hydrogen peroxide (H2O2) are quantified. Liquid phase microphysical scavenging was the dominant process reducing CH2O and H2O2outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH3OOH mixing ratios in the storm cores were primarily due to entrainment of low‐background CH3OOH. In the air mass storm, lower CH3OOH and H2O2scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH3OOH and H2O2. Overestimated rain and hail production in WRF‐Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH2O. Methyl hydroperoxide mixing ratios are decreased mainly by entrainment and liquid phase and mixed‐phase scavengingHydrogen peroxide and formaldehyde mixing ratios affected more by liquid phase scavenging than by entrainment or aqueous chemistryOverestimated rain/hail production in WRF‐Chem reduces confidence in ice retention fraction values determined for peroxides and formaldehyde

Deep convective transport of surface moisture and pollution from the planetary boundary layer to the upper troposphere and lower stratosphere affects the radiation budget and climate. This study analyzes the deep convective transport in three different convective regimes from the 2012 Deep Convective Clouds and Chemistry field campaign: 21 May Alabama air mass thunderstorms, 29 May Oklahoma supercell severe storm, and 11 June mesoscale convective system (MCS). Lightning data assimilation within the Weather Research and Forecasting (WRF) model coupled with chemistry (WRF‐Chem) is utilized to improve the simulations of storm location, vertical structure, and chemical fields. Analysis of vertical flux divergence shows that deep convective transport in the 29 May supercell case is the strongest per unit area, while transport of boundary layer insoluble trace gases is relatively weak in the MCS and air mass cases. The weak deep convective transport in the strong MCS is unexpected and is caused by the injection into low levels of midlevel clean air by a strong rear inflow jet. In each system, the magnitude of tracer vertical transport is more closely related to the vertical distribution of mass flux density than the vertical distribution of trace gas mixing ratio. Finally, the net vertical transport is strongest in high composite reflectivity regions and dominated by upward transport. Lightning data assimilation improves model simulations of storm location and vertical structureRear inflow jets within mesoscale convective systems may weaken boundary layer trace gas vertical transportThe tracer vertical transport is more controlled by the vertical gradient of mass flux than the vertical gradient of trace gas

We evaluate nitrogen oxide (NOx= NO + NO2) production from lightning over the Gulf of Mexico region using data from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite along with detection efficiency‐adjusted lightning data from the World Wide Lightning Location Network (WWLLN). A special algorithm was developed to retrieve the lightning NOx(LNOx) signal from OMI. The algorithm in its general form takes the total slant column NO2from OMI and removes the stratospheric contribution and tropospheric background and includes an air mass factor appropriate for the profile of lightning NOxto convert the slant column LNO2to a vertical column of LNOx. WWLLN flashes are totaled over a period of 3 h prior to OMI overpass, which is the time an air parcel is expected to remain in a 1° × 1° grid box. The analysis is conducted for grid cells containing flash counts greater than a threshold value of 3000 flashes that yields an expected LNOxsignal greater than the background. Pixels with cloud radiance fraction greater than a criterion value (0.9) indicative of highly reflective clouds are used. Results for the summer seasons during 2007–2011 yield mean LNOxproduction of ~80 ± 45 mol per flash over the region for the two analysis methods after accounting for biases and uncertainties in the estimation method. These results are consistent with literature estimates and more robust than many prior estimates due to the large number of storms considered but are sensitive to several substantial sources of uncertainty. Realistic seasonal mean values of lightning NOx(LNOx) production can be obtained from OMI dataMean LNOxproduction over the Gulf of Mexico for five summers is 80 ± 45 mol per flash when adjusted for biases and uncertaintiesBiases and uncertainties in LNOxestimates stemming from OMI data, elements of the algorithm, and flash data are quantified

We examine wet scavenging of soluble trace gases in storms observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. We conduct high‐resolution simulations with the Weather Research and Forecasting model with Chemistry (WRF‐Chem) of a severe storm in Oklahoma. The model represents well the storm location, size, and structure as compared with Next Generation Weather Radar reflectivity, and simulated CO transport is consistent with aircraft observations. Scavenging efficiencies (SEs) between inflow and outflow of soluble species are calculated from aircraft measurements and model simulations. Using a simple wet scavenging scheme, we simulate the SE of each soluble species within the error bars of the observations. The simulated SEs of all species except nitric acid (HNO3) are highly sensitive to the values specified for the fractions retained in ice when cloud water freezes. To reproduce the observations, we must assume zero ice retention for formaldehyde (CH2O) and hydrogen peroxide (H2O2) and complete retention for methyl hydrogen peroxide (CH3OOH) and sulfur dioxide (SO2), likely to compensate for the lack of aqueous chemistry in the model. We then compare scavenging efficiencies among storms that formed in Alabama and northeast Colorado and the Oklahoma storm. Significant differences in SEs are seen among storms and species. More scavenging of HNO3and less removal of CH3OOH are seen in storms with higher maximum flash rates, an indication of more graupel mass. Graupel is associated with mixed‐phase scavenging and lightning production of nitrogen oxides (NOx), processes that may explain the observed differences in HNO3and CH3OOH scavenging. Observed deep convective scavenging efficiencies simulated by simple schemeSimulated scavenging efficiencies highly sensitive to ice retention fractionScavenging efficiencies vary among storms with different microphysics

Nitrogen oxides produced by lightning (LNOx) play an important role in determining mid‐ and upper‐tropospheric concentrations of the hydroxyl radical (OH), methane (CH4), and ozone (O3). The moles of NOxproduced per flash was examined using nitrogen dioxide (NO2) columns and cloud properties from the Tropospheric Monitoring Instrument (TROPOMI) and flash counts from the Geostationary Lightning Mapper (GLM) aboard the Geostationary Operational Environmental Satellite‐16 (GOES‐16) and Earth Networks Total Lightning Network (ENTLN) for 29 convective systems over the United States that occurred during 2018 and 2019. For each of the case studies, the LNOxproduction efficiency (PE) was estimated using TROPOMI pixels over deep convection. First, the NOxcolumns associated with the TROPOMI NO2columns were estimated using a specially derived air mass factor (AMF). The tropospheric column due to recent lightning was then determined by subtracting from the median NOxcolumn a background representative of the NOxcolumn due to sources other than recent lightning. Then, the PE was calculated by multiplying the LNOxcolumn by the storm area and dividing by the number of flashes contributing to the column. For a three‐hour chemical lifetime, the mean PE was found to be 175 ± 100 mol per flash for optical flashes from GLM and 120 ± 65 mol per flash for radio‐wave‐detected flashes from ENTLN. The uncertainty associated with these values is mostly due to uncertainties in tropospheric background, AMF, and detection efficiency. GLM PE for individual systems was found to be positively correlated with optical energy. Lightning produces nitrogen oxides (NOx) as the extreme temperatures within lightning channels break apart molecular nitrogen (N2) and oxygen (O2). NOxproduced by lightning (LNOx) plays an important role in determining mid‐ and upper‐tropospheric concentrations of the hydroxyl radical (OH), the atmosphere’s cleanser; methane (CH4), an especially potent greenhouse gas; and ozone (O3), a greenhouse gas and pollutant. In this study, NOxproduction per lightning flash was examined for 29 convective systems over the eastern‐ and central‐ United States that occurred during the warm seasons of 2018 and 2019 using nitrogen dioxide (NO2) retrievals and cloud properties from the Tropospheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel‐5 Precursor satellite and lightning flash counts from a satellite‐based Geostationary Lightning Mapper (GLM) and the ground‐based Earth Networks Total Lightning Network (ENTLN). The mean moles of NOxproduced per flash was found to equal ∼180 moles per flash for optically detected flashes from GLM and ∼120 moles per flash for radio‐signal‐detected flashes from ENTLN. These values are on the lower end of the commonly cited range of 100–500 moles per flash for midlatitude flashes. NO2columns from Tropospheric Monitoring Instrument (TROPOMI) are used to estimate NOxproduction per flashMean NOxproduction by optically detected lightning flashes equals 175 ± 100 mol per flash for 29 case studies over the United StatesMean NOxproduction by radio‐signal‐detected lightning flashes equals 120 ± 65 mol per flash for 29 case studies over the United States NO2columns from Tropospheric Monitoring Instrument (TROPOMI) are used to estimate NOxproduction per flash Mean NOxproduction by optically detected lightning flashes equals 175 ± 100 mol per flash for 29 case studies over the United States Mean NOxproduction by radio‐signal‐detected lightning flashes equals 120 ± 65 mol per flash for 29 case studies over the United States

A primary goal of the Geostationary Operational Environmental Satellite R‐series Post Launch Test (GOES‐R PLT) Field Campaign during spring 2017 was the performance evaluation of the Geostationary Lightning Mapper (GLM) aboard the GOES‐16 satellite. The NASA Goddard Geo‐CAPE Airborne Simulator (GCAS), an ultra‐violet visible spectrometer, piggybacked on the aircraft mission to allow continuous hyper‐spectral measurements at high spectral and spatial resolutions simultaneously with optical lightning detection by the Fly’s Eye GLM Simulator while overflying convective systems. NO2columns retrieved from GCAS were used to estimate the moles of NOxproduced per flash, referred to as lightning NOxproduction efficiency (LNOxPE) for convective systems over the United States and western Atlantic. The mean PE was determined to be 360 ± 180 mol per flash for optically detected GLM flashes and 230 ± 115 mol per flash for radio‐wave detected Earth Networks Total Lightning Network flashes. These values span the commonly cited range of 100–500 mol per flash for midlatitude flashes. LNOxPE was found to be positively correlated with GLM flash multiplicity and flash optical energy but negatively correlated with flash density. The positive correlations provide encouragement for PE parameterizations in terms of flash energy or multiplicity. Observations during the GOES‐R PLT field campaign provide a preview of the analysis that will be possible when continuous lightning detection is coupled with hourly NO2columns from a geostationary instrument such as Tropospheric Emissions: Monitoring of Pollution. A goal of the Geostationary Operational Environmental Satellite R‐series Post Launch Test (GOES‐R PLT) Field Campaign during spring 2017 was evaluation of the Geostationary Lightning Mapper (GLM) aboard the GOES‐16 satellite. The NASA Goddard Geo‐CAPE Airborne Simulator (GCAS) piggybacked on the aircraft allowing for continuous column measurements of NO2, a member of the nitrogen oxide family (NOx) that is also an ozone precursor. NO2columns from GCAS were used to estimate the moles of NOxproduced per lightning flash for 10 convective systems over the United States and western Atlantic. The moles of NOxproduced per flash was determined to be approximately 360 mol per flash for optically detected GLM flashes and 230 mol per flash for radio‐wave detected Earth Networks Total Lightning Network flashes. These values span the commonly cited range of 100–500 mol per flash for midlatitude flashes. Observations during the GOES‐R PLT field campaign provide a preview of the analysis that will be possible when continuous lightning detection is coupled with NO2columns from a geostationary instrument such as Tropospheric Emissions: Monitoring of Pollution. NO2columns from Goddard Geo‐CAPE Airborne Simulator are used to estimate NOxproduction per flashNOxproduction by lightning detected by the Geostationary Lightning Mapper over the United States is found to equal 360 mol per flashNOxproduction per flash is positively correlated with flash multiplicity and optical energy but negatively correlated with flash density NO2columns from Goddard Geo‐CAPE Airborne Simulator are used to estimate NOxproduction per flash NOxproduction by lightning detected by the Geostationary Lightning Mapper over the United States is found to equal 360 mol per flash NOxproduction per flash is positively correlated with flash multiplicity and optical energy but negatively correlated with flash density

We describe the resources used, the deployment strategy, and the outcomes of the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) experiment, which took place in the summer of 2014 in the Front Range of Colorado. We provide a history of air quality of the region and the outcomes of previously conducted experiments, describe the atmospheric conditions encountered during the campaign, and summarize the scientific findings that the campaign produced, together with the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) intensive, simultaneously carried out by the National Aeronautics and Space Administration. The goal of FRAPPÉ was to measure emission tracers and photochemical tracers from the ground and by aircraft to be able to quantify the contributions of various emission sectors to the photochemical production of ozone in the Colorado Front Range. We found major contributions from the fossil fuel extraction sector as well as the transportation sector, with minor contributions from agriculture, energy generation, and industry. The meteorological conditions were also found to be critical in creating situations conducive to high ozone in the area. We describe the deployment and the outcomes of the FRAPPÉ experiment, which took place in the summer of 2014 in the Front Range of ColoradoThe goal of the campaign was to quantify the contributions of various emission sectors to ozone produced in the regionMajor contributors to photochemical ozone production were identified as emissions from transportation and from the oil and gas sector. Meteorological conditions were also found to be critical for high‐ozone episodes