First Simulations of Lighthing Optical Observations during Daytime in the Context of the C³IEL Mission

For over two decades, optical observations from low Earth orbit satellites have enabled the creation of the first global map of lightning activity. Today, the latest generation of geostationary meteorological satellites, such as the European Meteosat Third Generation (MTG) Lightning Imager (LI), is equipped with lightning imagers. Additionally, instruments like the Lightning Imaging Sensor (LIS) and the Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station detect optical lightning signals across various wavelengths, ranging from near-UV to near-IR, with cameras and photometers.

Understanding the radiative transfer of light generated by lightning discharges within clouds is crucial for interpreting detected optical signals. In this work, the three-dimensional radiative transfer code 3DMCPOL (Cornet et al., 2010) is adapted to simulate realistic lightning waveforms and images. The 3DMCPOL code simulates light propagation through three-dimensional atmospheres using the Monte Carlo method, originally for solar or thermal sources. A realistic four-dimensional (time and space) lightning source was implemented (Rimboud et al., 2024), and its detection by ground-based or space-borne photometers and cameras.

The methodology will first be detailed, focusing on how realistic imagery observations are simulated using geometric models of the Lightning Optical Imager (LOI) developed by the French space agency for the French-Israeli C³IEL (Cluster for Cloud Evolution, Climate, and Lightning) mission currently under development. Then, simulations of realistic daytime LOI observations will be presented using the microphysical outputs of the French cloud-resolving model Meso-NH for the cloud description. First results on the necessary acquisition frequency for background scenes and the impact of tilted observations on lightning detection, will be discussed from these simulations.