The Role of Global Thunderstorm Activity in Modulating Global Cirrus Clouds

Cirrus clouds provide a significant radiative forcing on the Earth's climate system. The net cloud radiative forcing for cirrus clouds results a warming of the climate.  More/less cirrus clouds result in more/less warming of the planet. The moisture for the formation of cirrus clouds in the upper atmosphere is transported there in large part via deep convective storms, many associated with lightning activity and hence defined as thunderstorms.  An increasing in cirrus clouds in a warmer atmosphere will amplify the initial warming. This paper looks at the connection in space and time between monthly mean lightning activity observed from the Lightning Imaging Sensor on board the International Space Station (LIS-ISS), and the global monthly mean cirrus cloud cover obtained from the MERRA-2 reanalysis product. The correlation coefficient between the global monthly mean cloud optical thickness (COT) of the cirrus clouds (clouds at altitudes above the 400hPa pressure levels) with the monthly mean lightning flash counts is 0.84, implying that monthly mean  lightning can explain 70% of monthly variability of the global high cloud optical thickness. In addition, lightning amount explains nearly 60% of the monthly mean global area coverage of cirrus clouds.  Given these statistically significant connections between lightning and cirrus clouds, we propose using global lightning data as an additional tool for monitoring monthly variability of cirrus clouds.