Lightning: An Essential Climate Variable

Observations of lightning are commonplace worldwide and recent satellite instruments in geostationary and low earth orbit provide enhanced global coverage complementing the coverage of ground-based networks. Lightning can be used for monitoring severe convection and precipitation, improving estimates of severe storm development, evolution and intensity, and hence provide early warnings for severe weather phenomena. In addition, lightning itself impacts the global climate by producing wildfires and nitrogen oxides (NO_X), a precursor of tropospheric ozone that acts as a strong greenhouse gas. For climate variability and change monitoring, lightning has been shown to follow trends and extremes in convective storms and track global surface air temperature on many natural time scales. Additionally, lightning is closely related to strong convective updraft regions which carry the NOx and other trace gases into the stratosphere which couples the troposphere and stratosphere chemistry. Recent reports from ground-based lightning networks of increased lightning activity in the Arctic may serve as an early indication of greater storminess in a changing climate. Furthermore, lightning intensity in thunderstorms is well correlated with the amounts of upper tropospheric water vapor, that can amplify surface warmings from greenhouse gases (positive feedbacks).

Given this relevance and relationship to other climate variables, lightning has been added to the list of Essential Climate Variables (ECV) in the WMO Global Climate Observing System Implementation Plan (IP), including the initial requirements for climate monitoring with lightning measurements (https://gcos.wmo.int/en/essential-climate-variables/table). A Task Team on lightning observations for climate applications completed an initial study that explains the relevance of lightning observations, describes the current status of observations, discusses gaps and open research questions and provides suggestions for monitoring requirements for lightning, metadata and reprocessing, and value-added products such as flash altitude, flash type, Thunder Days and Thunder Hours. The Task Team has identified relevant data sets to address climate questions using information about lightning. In this presentation we present an initial look at the lightning climatology and regional frequency distributions as depicted by space-based and ground-based networks, highlighting lightning variability and trends during the reduction of industrial activity and aerosols accompanying the COVID19 pandemic that took place during the 2020-2023 triple-dip 3-year La Niña, the colder counterpart of the El Niño underway since March 2023. Lastly, we address important considerations for the production and public access of a community climate data set for lightning.

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