Sunlight unlocks secrets to how Earth works

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When our planet and the incoming sunlight align just right, stunning phenomena such as rainbows and halos can occur. More often, sunlight - or shortwave radiation - interacts with Earth in subtle but curious ways.

A Sun halo —one of countless ways sunlight interacts with our planet. Credit Si Gao

A new perspective study, published in Advances in Atmospheric Sciences, lays out how shortwave radiation research has led to improved fundamental understanding of Earth. The study also shares exciting prospects for how such advances can continue into the future.

Scientific insights derived from shortwave radiation have an extensive history. “There has traditionally been a lot of interest in understanding shortwave radiation variability” said author Jake Gristey with the University of Colorado’s CIRES, also affiliated with LASP and NOAA’s Chemical Sciences Laboratory. “Real world applications that directly benefit society are numerous, from agriculture to renewable energy to air quality”.

In the new study, Gristey highlights three examples of shortwave radiation research that have received notable recent attention.

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First, a key challenge for current computer models of the atmosphere is pointed out: shortwave radiation is almost always represented in a series of separate columns. “Shortwave radiation transport in the horizontal direction - or between columns - is therefore unaccounted for” said Gristey. It is shown that horizontal shortwave radiation transport will be increasingly important for accurate simulations as atmospheric models continue to move toward finer spatial grids, demanding new research.

Second, satellite measurement gaps at different times of the day are discussed. “Shortwave radiation reflected by Earth can change drastically throughout the day, but many satellites only measure limited parts of the day” Gristey added. He argues that recent developments in small satellite technology and sensor miniaturization could be used to address this important measurement gap with a cost-effective constellation of small satellites in the near future.

Third, the spectral structure of shortwave radiation is addressed. “Shortwave radiation is actually composed of a spectrum of different colors – or wavelengths – that hold vast information” claimed Gristey. It is demonstrated that changes in the Earth’s surface and atmosphere could be inferred from satellite measurements of spectral reflected shortwave radiation. Gristey expects an upcoming fleet of satellites to fuel further advances in utilizing spectral shortwave radiation to understand Earth.

The new study is part of a special issue for the International Radiation Symposium 2024, where Gristey delivered a lecture on these perspectives as recipient of the 2024 International Radiation Commission Young Scientist Award.