The Role of Global Thunderstorm Activity in Modulating Global Cirrus Clouds

Abstract

Cirrus clouds provide a significant radiative forcing on the Earth's climate system. 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, 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 of the cirrus clouds (clouds at altitudes above the 400 hPa 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.

Revisiting the Link Between Thunderstorms and Upper Tropospheric Water Vapor

“…Given the results in this and previous studies, we propose using global thunderstorm observations as a proxy for tracking the variability and trends in UTWV, and maybe even global cirrus clouds (Saha, Price, & Guha, 2023). In previous studies (Price, 2000; Price & Asfur, 2006), the global lightning data used was from ELF networks that cannot provide spatial resolution of thunderstorms around the globe.…”

“…Both water vapor and thin cirrus clouds act to trap infrared radiation emitted at the Earth's surface, and hence both act to reduce the outgoing longwave radiation (OLR) from the Earth. As a result, any future increase in global or regional thunderstorm activity (Price & Rind, 1994; Romps et al., 2014) would imply more UTWV and cirrus clouds in the tropical tropopause region (Kent et al., 1995; Saha, Price, & Guha, 2023), with implications for positive feedbacks on the climate system.…”

“…Water vapor in the upper troposphere is also a main source of moisture for the production of cirrus clouds (Saha, Price, & Guha, 2023). Both water vapor and thin cirrus clouds act to trap infrared radiation emitted at the Earth's surface, and hence both act to reduce the outgoing longwave radiation (OLR) from the Earth.…”

“…Around thunderstorms the cirrus anvils are often optically thick and hence have a net cooling effect on surface temperatures. However, the large majority of global cirrus clouds have low optical depths ( τ < 2) (Katagiri & Nakajima, 2004) that result in a net warming effect on the Earth's climate (Saha, Price, & Guha, 2023; Saha, Price, Plotnik, & Guha, 2023; Zhou et al., 2014).…”

“…In addition to trapping in extra heat, water vapor in the atmosphere also plays a significant role in forming clouds, and hence impacting the albedo and the greenhouse effect of the planet (Saha, Price, & Guha, 2023). Moreover, water vapor is also essential in atmospheric chemistry (Kley, 1997; Wu et al., 2018), assisting in numerous reactions to cleanse the atmosphere from pollutants.…”