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New study sheds light on chemical involved in ozone destruction

LOS ANGELES, April 28 — US scientists have found new evidence that nighttime temperatures can affect chlorine monoxide, a key chemical that plays a role in ozone destruction, it was announced on Wednesday.

The new evidence leads to better understanding of how polar chlorine monoxide behaves at night at the lowest temperatures of the stratosphere, Earth's second lowest atmospheric layer, NASA's Jet Propulsion Laboratory (JPL) said in a press release.

Until now, scientists have not been able to conduct appropriate laboratory experiments relevant to the matter, according to the release.

Combining NASA satellite measurements with a state-of-the-art chemical model, a team of JPL scientists found this relationship to be more consistent with recent laboratory work than with some older laboratory and field observational data, the release said.

The data came from the Microwave Limb Sounder instrument on NASA's Aura satellite.

"Our comprehensive study uses multiple years of Arctic and Antarctic satellite observations to quantify the nighttime balance of ozone-destroying chlorine chemical compounds," said lead researcher Michelle Santee.

"By gaining a better knowledge of this balance, scientists will be able to make more accurate predictions of polar ozone loss, especially in twilight and in the Arctic, where conditions are often only marginally favorable for ozone destruction."

At night, chlorine monoxide molecules combine to form chlorine peroxide, and the balance between these two chemicals is highly temperature-sensitive. Studying this balance quantitatively is challenging. Previous studies in the laboratory and using aircraft and satellites had found significantly different degrees of balance.

The Microwave Limb Sounder's very large number of measurements has quantified this balance far better than before, according to the JPL, which is headquartered in Pasadena, Los Angeles.

Since its launch in 2004, the Microwave Limb Sounder has monitored most of the polar regions of both hemispheres daily, compiling tens of thousands of measurements of nighttime chlorine monoxide levels, along with various other chemicals, including ozone.

These data allow scientists to test their understanding of chlorine-related chemistry on an unprecedented scale, the JPL said. (PNA/Xinhua) vcs/utb

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