The phrase "polar stratosphere" refers to the layer of Earth's atmosphere that is found high above the poles. It is where the ozone layer is located, which shields us from harmful ultraviolet rays from the sun. Full definition
«It is worth investigating if the mechanisms identified in the laboratory carry over to the polar stratosphere,» he says. (newscientist.com)
Such sulfuric acid aerosols are already responsible for the bulk of nacreous clouds that form in the polar stratosphere; added particles would just amp up the natural process (although it might also amp up damage the ozone layer). (scientificamerican.com)
Investigating the polar stratosphere under the impact of climate change is the goal of the measurement campaign «The Polar Stratosphere in a Changing Climate» (POLSTRACC), carried out with the German research aircraft HALO. (sciencedaily.com)