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. Such 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 extremely low-frequency (ELF) sensors and by optical instruments located in space. 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 develop a global parameterization that uses vertical velocity at the 450 hPa pressure level as a proxy for the ratio of LCC to total lightning in thunderstorms. We implement this parameterization into the LNOX submodel of the Modular Earth Submodel System (MESSy) for usage within the European Center HAMburg general circulation model (ECHAM)/MESSy Atmospheric Chemistry (EMAC) model and compare the observed and simulated climatologies of LCC lightning flashes using six different lightning parameterizations. We find that the best agreement between the simulated and 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.

Meteorological Conditions Associated with Lightning Ignited Fires and Long-Continuing-Current Lightning in Arizona, New Mexico and Florida

“…The details of the sensor and the reported climatology of lightning and LCC lightning between 1998 and 2014 can be found in [46][47][48][49][50][51]. We used the method globally developed by [51] and recently employed by Pérez-Invernón et al (2021) [20] (over the Mediterranean Basin) and Pérez-Invernón et al (2022) [21] (globally) to classify lightning flashes reported by TRMM-LIS according to the duration of the continuing phase. The duration of the continuing phase detected by TRMM-LIS should be considered a minimum.…”

“…The ignition phase is supposed to be influenced by the characteristics of the lightning discharge and the vegetation. Long-Continuing-Current (LCC) lightning with a duration between 40 ms and 282 ms have been proposed as the main precursors of LIW [18][19][20][21]. LCC lightning flashes transport a significant amount of electrical charge between the cloud and the attachment point.…”

Variation of lightning-ignited wildfire patterns under climate change

“…The LNOX submodel of MESSy estimates the total lightning flash density, the LCC lightning flash density, and the production of NO x by lightning by using different lightning parameterizations [15] and a scaling factor that ensures a global lightning occurrence rate of ∼45 flashes per second [46,60]. For the present study, we use the lightning parameterization based on the Cloud Top Height (CTH) [24] for land and on the convective precipitation [61] for ocean as proposed by Pérez-Invernón et al (2022) [25] and scaled by a factor of 1.13. This lightning parameterization overestimates the lightning flash density over the ocean with respect to land, producing a land/ocean contrast of about 1 : 1 instead of the 3 : 1 contrast reported by space-based instruments [46,47,60].…”

“…1b), suggesting that a variation in lightning frequency does not necessarily imply the same varia- 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 ) [15]. The MUMF have been multiplied by 6.57 as it is applied in the parameterization of LCC lightning [25]. Changes are calculated as the difference between RCP6.0 and present-day simulations.…”

“…The ratio of LCC to total lightning is parameterized using the updraft mass flux as proxy following Pérez-Invernón et al (2022) [25] (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.…”