[1] Nitrogen oxides (NOx ≡ NO + NO2) produced by lightning make a major contribution to the global production of tropospheric ozone and OH. Lightning distributions inferred from standard convective parameterizations in global chemical transport models (CTMs) fail to reproduce observations from the Lightning Imaging Sensor (LIS) and the Optical Transient Detector (OTD) satellite instruments. We present an optimal regional scaling algorithm for CTMs to fit the lightning NOxsource to the satellite lightning data in a way that preserves the coupling to deep convective transport. We show that applying monthly scaling factors over ∼37 regions globally significantly improves the tropical ozone simulation in the GEOS-Chem CTM as compared to a simulation unconstrained by the satellite data and performs equally well to a simulation with local scaling. The coarse regional scaling preserves sufficient statistics in the satellite data to constrain the interannual variability (IAV) of lightning. After processing the LIS data to remove their diurnal sampling bias, we construct a monthly time series of lightning flash rates for 1998–2010 and 35°S–35°N. We find a correlation of IAV in total tropical lightning with El Nino but not with the solar cycle or the quasi-biennial oscillation. The global lightning NOxsource ± IAV standard deviation in GEOS-Chem is 6.0 ± 0.5 Tg N yr−1, compared to 5.5 ± 0.8 Tg N yr−1 for the biomass burning source. Lightning NOx could have a large influence on the IAV of tropospheric ozone because it is released in the upper troposphere where ozone production is most efficient.

/pdf/optimized-regional-and-interannual-variability-of-lightning-4zipr4f373.pdf

Optimized regional and interannual variability of lightning in a global chemical transport model constrained by LIS/OTD satellite data

https://cyberleninka.org/article/n/108672.pdf

New indices for wet scavenging of air pollutants (O3, CO, NO2, SO2, and PM10) by summertime rain

Impact of the COVID-19 outbreak on air pollution levels in East Asia.

[1] The impact of nitric oxide (NO) emissions by lightning on summertime North American nitrogen oxides (NOx) and ozone is studied using the Global Modeling Initiative (GMI) CTM and an improved lightning NO algorithm. The spatial distributions of modeled and National Lightning Detection Network-based flash rates during the summers of 2004–2006 agree well (R2 = 0.49, 18% low bias). Despite this reasonable agreement, 9–12 km model NOx during the Intercontinental Chemical Transport Experiment (INTEX-A) campaign is a factor of 2.2–3.6 too low for a simulation that includes a 480 mol per flash midlatitude lightning NO source, the source that provides the best agreement with measurements. Possible causes of this low bias include biases in model convection and/or too rapid NOx chemistry in the upper troposphere. Model tropospheric NO2 columns over the southeastern United States during these summers show a 7% high bias with respect to the OMI DOMINO/GEOS-Chem tropospheric column NO2 product. Observed changes between 2004 and 2006 in upper tropospheric ozone at southeastern U. S. INTEX Ozonesonde Network Study sites are captured by the model and appear to be caused by a stronger upper tropospheric anticyclone in 2006 that led to an increase from 21 to 30 ppbv between 2004 and 2006 in the amount of ozone with a lightning NO source; lightning NO emissions were 15%–20% larger in 2004. The contribution of lightning NO to monthly average summertime 300 hPa NOx over the eastern United States during 2004–2006 varies from 61%–73% (0.09–0.16 ppbv), while the contribution to ozone varies from 19%–31% (15–24 ppbv).

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2010JD014062

Impact of lightning NO emissions on North American photochemistry as determined using the Global Modeling Initiative (GMI) model

We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in the Hadean atmosphere to be available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO3−) and nitrite (NO2−) are the most attractive high-potential electron acceptors for pulling and enabling crucial redox reactions of autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The Hadean atmosphere, dominated by CO2 and N2, will produce nitric oxide (NO) when shocked by lightning. Photochemical reactions involving NO and H2O vapor will then produce acids such as HNO, HNO2, HNO3, and HO2NO2 that rain into the ocean. There, they dissociate into or react to form nitrate and nitrite. We present new calculations based on a novel combination of early-Earth global climate model and photochemical modeling, and we predict the flux of NOx to the Hadean ocean. In our 0.1-, 1-, and 10-bar pCO2 models, we calculate the NOx delivery to be 2.4 × 105, 6.5 × 1...

/pdf/nitrogen-oxides-in-early-earth-s-atmosphere-as-electron-1prypswjih.pdf

Nitrogen Oxides in Early Earth's Atmosphere as Electron Acceptors for Life's Emergence

The migration of enhancements in NO_2 concentration, outgoing longwave radiation (OLR), and radiative effects associated with the onset of the North American Monsoon in July 2005 has been investigated using satellite data and the Regional Chemical Transport Model (REAM). The satellite data include the tropospheric NO2 columns, tropospheric O_3 profiles, and OLR from OMI, TES and NOAA-16 satellite, respectively, for June and July 2005. The simulated OLR captures the spatial distribution of the remotely sensed OLR fields with relatively small biases (≤5.7%) and high spatial correlations (R ≥ 0.88). This study reveals that the lightning-generated NOx exerts a larger, by up to a factor of three, impact on OLR (up to 0.35 Wm^(−2)) and radiative effects (up to 0.55 Wm^(−2)) by enhancing O_3 in the upper troposphere than anthropogenic NO_x that increases O_3 in the lower troposphere, despite the fact that the lightning-generated NO_x and O_3 are much smaller than those from the anthropogenic emissions. The radiative effect by lightning-derived upper tropospheric O_3 over the convective outflow regions is affected by the changes in lightning frequency. Thus the changes in convection due to global warming may alter the geographical distribution and magnitude of the radiative effect of lightning-derived O3, and this paper is a first step in quantifying the current radiative impact.

/pdf/lightning-and-anthropogenic-nox-sources-over-the-united-50k4iwshqj.pdf

Lightning and anthropogenic NOx sources over the United States and the western North Atlantic Ocean: Impact on OLR and radiative effects

Mesoscale convective systems are high impact convectively driven weather systems that contribute large amounts to the precipitation daily and monthly totals at various locations globally. As such, an understanding of the lifecycle, characteristics, frequency and seasonality of these convective features is important for several sectors and studies in climate studies, agricultural and hydrological studies, and disaster management. This study explores the applicability of graph theory to creating a fully automated algorithm for identifying mesoscale convective systems and determining their precipitation characteristics from satellite datasets. Our results show that applying graph theory to this problem allows for the identification of features from infrared satellite data and the seamlessly identification in a precipitation rate satellite-based dataset, while innately handling the inherent complexity and non-linearity of mesoscale convective systems.

Exploring a graph theory based algorithm for automated identification and characterization of large mesoscale convective systems in satellite datasets

Cool season precipitation event characteristics are evaluated across a suite of downscaled climate models over the northeastern US. Downscaled hindcast simulations are produced by dynamically downscaling the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) using the National Aeronautics and Space Administration (NASA)-Unified Weather Research and Forecasting (WRF) regional climate model (RCM) and the Goddard Earth Observing System Model, Version 5 (GEOS-5) global climate model. NU-WRF RCM simulations are produced at 24, 12, and 4-km horizontal resolutions using a range of spectral nudging schemes while the MERRA2 global downscaled run is provided at 12.5-km. All model runs are evaluated using four metrics designed to capture key features of precipitation events: event frequency, event intensity, even total, and event duration. Overall, the downscaling approaches result in a reasonable representation of many of the key features of precipitation events over the region, however considerable biases exist in the magnitude of each metric. Based on this evaluation there is no clear indication that higher resolution simulations result in more realistic results in general, however many small-scale features such as orographic enhancement of precipitation are only captured at higher resolutions suggesting some added value over coarser resolution. While the differences between simulations produced using nudging and no nudging are small, there is some improvement in model fidelity when nudging is introduced, especially at a cutoff wavelength of 600 km compared to 2000 km. Based on the results of this evaluation, dynamical regional downscaling using NU-WRF results in a more realistic representation of precipitation event climatology than the global downscaling of MERRA2 using GEOS-5.

Evaluation of cool season precipitation event characteristics over the Northeast US in a suite of downscaled climate model hindcasts

. Since sowing date of maize is sensitive to climate variability and changes, it is critical to examine how sowing dates affect maize yields in various temperature regimes in the southwestern US. In doing so, the ApsimRegions model, regionally extended version of the APSIM model, has been run over the southwestern US region at 32 km resolutions over the 21-year period from 1991 to 2011. The meteorological forcing dataset was North American Regional Reanalysis (NARR) and irrigation was assumed to be applied at a 95% soil water-holding capacity. The interannually-fixed and -variant sowing date runs (fixed and optimal run, respectively) showed 50~300 % increases of the yield potential over selected regions by optimizing sowing date. For the optimal run, it was found that earlier sowing dates are favorable for higher yields primarily by increasing the length of growing season in cold mountaineous regions. In these regions, warmer than normal conditions in the sowing period tend to advance the sowing date to result in yield increases. Over the low-elevation warm regions (e.g., the southern parts of the Central Valley and Arizona), yields are less correlated with sowing dates and the length of growing season, perhaps because growing season temperatures are high enough for fast growth. Instread, in those warm regions, maize yields are sensitive to temperature variations during the sowing- and late growing season due to the adverse effects of extremely high temperature events on maize development. Theses results indicate that appropriate adaptations for sowing date can enhance yield significantly, but the positive effect of advanced sowing on the maize yields in warmer spring is constrained in the cool environmental regions rather than the warm environmental regions in the southwestern US.

Jinwon Kim

Papers

Lightning and anthropogenic NOx sources over the United States and the western North Atlantic Ocean: Impact on OLR and radiative effects

Exploring a graph theory based algorithm for automated identification and characterization of large mesoscale convective systems in satellite datasets

Evaluation of cool season precipitation event characteristics over the Northeast US in a suite of downscaled climate model hindcasts

Temperature, Sowing and Harvest Dates, and Yield Potential of Maize in the Southwestern US☆