A parameterization of Long-Continuing-Current (LCC) lightning in the lightning submodel LNOX (version 3.0) of the Modular Earth Submodel System (MESSy, version 2.54)

Abstract

Abstract. Lightning flashes can produce a discharge in which a continuing electrical current flows for more than 40 ms. This type of flashes are proposed to be the main precursors of lightning-ignited wildfires and also to trigger sprite discharges in the mesosphere. However, lightning parameterizations implemented in global atmospheric models do not include information about the continuing electrical current of flashes. The continuing current of lightning flashes cannot be detected by conventional lightning location systems. Instead, these so-called Long-Continuing-Current (LCC) flashes are commonly observed by Extreme Low Frequency (ELF) sensors and by optical instruments located in space. Previous reports of LCC lightning flashes tend to occur in winter and oceanic thunderstorms, which suggests a connection between weak convection and the occurrence of this type of discharge. In this study, we develop a parameterization of LCC lightning flashes based on a climatology derived from optical lightning measurements reported by the Lightning Imaging Sensor (LIS) on-board the International Space Station (ISS) between March 2017 and March 2020. We use meteorological data from reanalyses to find a global parameterization that uses the vertical velocity at 450 hPa pressure level as a proxy for the ratio of LCC to typical lightning in thunderstorms. We implement this parameterization into the LNOX submodel of the Modular Earth Submodel System (MESSy) for usage within the EMAC model, and compare the observed and the simulated climatologies of LCC lightning flashes using six different lightning parameterizations. We find that the best agreement between the simulated and the observed spatial distribution is obtained when using a novel combined lightning parameterization based on the cloud top height over land and on the convective precipitation over ocean.

Variation of lightning-ignited wildfire patterns under climate change

“…The ratio of LCC to total lightning is parameterized using the updraft mass flux as proxy following Pérez-Invernón et al (2022) 26 (see “Methods”). Thus, LCC lightning projections are driven not only by the influence of the climate on lightning, but also by the influence of climate on the updraft strength in thunderstorms.…”

“…2 e). The applied parameterization of LCC lightning 26 imposes an opposite relationship between the ratio of LCC to total lightning and the updraft in thunderstorms with high updraft mass fluxes (above ~ 0.2 kg m −2 s −1 ). This can be seen in the predicted trend of opposite direction of the mean updraft mass flux and the ratio of LCC to total lightning in some regions, as in South America, the coasts of North America, the Atlantic Ocean, Western Europe and the mainland of Asia.…”

“…The criterion to consider the MUMF in the calculation of the annual average is that the cloud thickness is at least 3 km and that the lightning occurrence rate is larger than 1.433 × 10 −14 m −2 s −1 ) 16 . The MUMF have been multiplied online by 6.57 as it is applied in the parameterization of LCC lightning 26 . Changes are calculated as the difference betweenthe Representative Concentration Pathway RCP6.0 and present-day simulations.…”

“…Prior to the simulation, we confirm the role of continuing current in lightning ignitions by comparing optical lightning data reported by the Geostationary Lightning Mapper (GLM) with forest fire occurrence data provided by the U.S. Department of Agriculture. We use the LCC lightning parameterization implemented by Pérez-Invernón et al (2022) 26 in the Modular Earth Submodel System (MESSy) for usage within the ECHAM / MESSy Atmospheric Chemistry (EMAC) model. The LCC lightning parameterization is implemented as a complement of the total lightning parameterizations.…”

Optical observations of thunderstorms from the International Space Station: recent results and perspectives

“…Some recent publications based on ISS-LIS measurements discuss the cross-correlation of ground-based lightning detection systems to estimate the detection efficiencies of measurement techniques such as the LINET 3D system 39 and a lightning detection network in China 40 . Other papers study the quantification of NO X based on lightning and TROPOMI measurements 41 , parametrization of NO X -production in continuing currents 42 , and meteorological conditions for lightning-ignited fires 43 .…”