Preprints
https://doi.org/10.5194/egusphere-2023-301
https://doi.org/10.5194/egusphere-2023-301
03 Apr 2023
 | 03 Apr 2023

Historical (1960–2014) lightning and LNOx trends and their controlling factors in a chemistry–climate model

Yanfeng He and Kengo Sudo

Abstract. Lightning can cause natural disasters that engender human and animal injuries or fatalities, infrastructure destruction, and wildfire ignition. Lightning-produced NOx (LNOx), a major NOx (NOx = NO + NO2) source, plays a vital role in atmospheric chemistry and global climate. The Earth has experienced marked global warming and changes in aerosol and aerosol precursor emissions (AeroPEs) since the 1960s. Investigating long-term historical (1960–2014) lightning and LNOx trends can provide important indicators for all lightning-related phenomena and for LNOx effects on atmospheric chemistry and global climate. Understanding how global warming and changes in AeroPEs influence historical lightning–LNOx trends is also helpful because it can provide a scientific basis for assessing future lightning–LNOx trends. Moreover, global lightning activities’ responses to large volcanic eruptions (such as the 1991 Pinatubo eruption) are not well elucidated, and are worth exploring. This study used the widely used cloud top height lightning scheme (CTH scheme) and the newly developed ice-based ECMWF-McCAUL lightning scheme to investigate historical (1960–2014) lightning–LNOx trends and variations and their controlling factors (global warming, increases in AeroPEs, and Pinatubo eruption) in the framework of the CHASER (MIROC) chemistry–climate model. Results of sensitive experiments indicate that both lightning schemes simulated almost flat global mean lightning flash rate trends during 1960–2014 in CHASER. Moreover, both lightning schemes suggest that past global warming enhances historical trends of global mean lightning density and global LNOx emissions in a positive direction (around 0.03 % yr−1 or 3 % K−1). However, past increases in AeroPEs exert an opposite effect to the lightning–LNOx trends (−0.07 % yr−1 – −0.04 % yr−1 for lightning and −0.08 % yr–1 – −0.03 % yr–1 for LNOx). Additionally, effects of past global warming and increases in AeroPEs on lightning trends were found to be heterogeneous across different regions when analyzing lightning trends on the global map. Lastly, this study is the first to suggest that global lightning activities were suppressed markedly during the first year after the Pinatubo eruption shown in both lightning schemes (global lightning activities decreased by as much as 17.02 % simulated by the ECMWF-McCAUL scheme). Based on the simulated suppressed lightning activities after the Pinatubo eruption, our study also indicates that global LNOx emissions decreased after the Pinatubo eruption (2.41 % – 8.72 % for the annual percentage reduction), which lasted 2–3 years. Model intercomparisons of lightning flash rate trends and variations between our study (CHASER) and other Coupled Model Intercomparison Project Phase 6 (CMIP6) models indicate significant uncertainties in historical (1960–2014) global lightning trend simulations. Such uncertainties must be investigated further.

Yanfeng He and Kengo Sudo

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-301', Anonymous Referee #1, 28 Apr 2023
  • RC2: 'Comment on egusphere-2023-301', Anonymous Referee #2, 02 May 2023

Yanfeng He and Kengo Sudo

Yanfeng He and Kengo Sudo

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Short summary
Lightning has big social impacts. The lightning-produced NOx (LNOx) plays a vital role in atmospheric chemistry and climate. Investigating past lightning–LNOx trends can provide essential indicators for all lightning-related phenomena. Simulation results show flat global lightning–LNOx trends during 1960–2014. Past global warming enhances the trends positively, but increases in aerosol have the opposite effect. We also suggest that global lightning decreased markedly after the Pinatubo eruption.