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

The International Space Station (ISS) is in the lowest available orbit at ~400 km altitude, bringing instruments as close to the atmosphere as possible from the vantage point of space. The orbit inclination is 51.6°, which brings the ISS over all the low- and mid-latitude regions of the Earth and at all local times. It is an ideal platform to observe deep convection and electrification of thunderstorms, taken advantage of by the Lightning Imaging Sensor (LIS) and the Atmosphere Space Interaction Monitor (ASIM) experiments. In the coming years, meteorological satellites in geostationary orbit (~36,000 km altitude) will provide sophisticated cloud and lightning observations with almost complete coverage of the Earth's thunderstorm regions. In addition, Earth-observing satellite instruments in geostationary- and low-Earth orbit (LEO) will measure more atmospheric parameters at a higher resolution than we know today. The new infrastructure in space offers an opportunity to advance our understanding of the role of thunderstorms in atmospheric dynamics and climate change. Here, we discuss how observations from the ISS or other LEO platforms with instruments that view the atmosphere at slanted angles can complement the measurements from primarily nadir-oriented instruments of present and planned missions. We suggest that the slanted viewing geometry from LEO may resolve the altitude of electrical activity and the cloud structure where they occur, with implications for modelling thunderstorms' effects on the atmosphere's radiative properties and climate balance.

Variation of lightning-ignited wildfire patterns under climate change.

Lightning is the main precursor of natural wildfires and Long-Continuing-Current (LCC) lightning flashes are proposed to be the main igniters of lightning-ignited wildfires (LIW). Previous studies predict a change of the global occurrence rate and spatial pattern of total lightning. Nevertheless, the sensitivity of lightning-ignited wildfire occurrence to climate change is uncertain. Here, we investigate space-based measurements of LCC lightning associated with lightning ignitions and present LCC lightning projections under the Representative Concentration Pathway RCP6.0 for the 2090s by applying a recent LCC lightning parameterization based on the updraft strength in thunderstorms. We find a 41% global increase of the LCC lightning flash rate. Increases are largest in South America, the western coast of North America, Central America, Australia, Southern and Eastern Asia, and Europe, while only regional variations are found in northern polar forests, where fire risk can affect permafrost soil carbon release. These results show that lightning schemes including LCC lightning are needed to project the occurrence of lightning-ignited wildfires under climate change.