The coupling of lightning, climate and air quality across multiple time horizons

Abstract:

Climate change can affect atmospheric composition through perturbation of natural processes, leading to complex feedbacks across a range of spatial and temporal scales. The primary atmospheric oxidants OH and ozone are very sensitive to emissions of nitrogen oxides (NOx) from lightning, and therefore so are the subsequent chemical perturbations to long-lived greenhouse gases (e.g., methane) and aerosol chemistry and physics. Meanwhile, cloud electrification responds to both meteorology and composition (aerosol particles). Key to understanding the ultimate impact of lightning on air quality and climate is the long-term methane feedback. Here, simulations are presented from the GISS ModelE2 chemistry-climate model in in which the response of Earth’s radiative budget and composition to lightning NOx is isolated in the present and future by allowing the model to re-equilibrate following removal of the source. Whereas lightning initially contributes to surface ozone enhancements, longer-term feedbacks via methane reduce surface ozone on multi-decadal time scales in the northern midlatitudes. These methane feedbacks lead to a strong negative radiative forcing in the present day from lightning NOx (-0.6 W m-2), several times stronger than that estimated for the anthropogenic NOx source. In addition to influencing tropospheric composition, lightning significantly impacts stratospheric dynamics and composition. In addition to the lightning work, I will also introduce a pilot methane and carbon dioxide monitoring network and inverse modeling framework that is presently being installed to aid New York State in assessing and meeting its greenhouse-gas reduction goals.