The phrase "under a clear sky" is grammatically correct and can be used in written English.
It is typically used to describe the weather or the setting of a particular scene. Example: We decided to have a picnic under a clear sky, enjoying the warm sun and fresh air.
Under a clear sky, the campus was quiet.
At midnight I woke under a clear sky and gibbous moon and walked along the brook.
It was weird to run under a clear sky while dark, brooding thunderheads flanked us on both sides.
Under a clear sky the predicted temperature gain by using a high reflectance material compared to a regular one on an unheated greenhouse was approximately 4 °C.
But Marion Rolland of France raced to victory under a clear sky on the 1.9-mile Streicher course, in 1 minute 50 seconds.
"I do photography at night under a clear sky, and a big full moon bright enough to read a paper by," Mr. Bloom said.
But the crowd, sitting under a glaring sun and a clear sky, loved it when he stated the obvious: that Mr. Bush's term is almost done.
The test was performed on the 23rd of August in Osaka, Japan, under a clear-sky weather condition (Fig. 7).
Thousands of workers, released from their offices in Lower Manhattan but with no way to get home except by foot, set off in vast streams, down the avenues and across the bridges under a beautiful, clear sky, accompanied by the unceasing serenade of sirens.
Search and recovery crews in Kazakhstan retrieved the American space tourist Richard Garriott, 47, and the Russian cosmonauts Sergei Volkov and Oleg Kononenko from the Soyuz module, which landed on its side on the brushy steppe of north-central Kazakhstan under a cold, clear sky.
We use our 1-D model to generate a spectrum of a planet dominated by each of the surfaces listed above under an Earth-like atmosphere in a clear-sky (no cloud) scenario.
