First measurement of the long searched for nitric acid crystals in polar stratospheric clouds

November 30, 2000

During the winter months in altitudes between 15 and 25 km polar stratospheric clouds (PSCs) are always observed above Antarctica and often over the northern polar region. PSCs form at low temperatures through condensation of water and nitric acid on sulfuric acid aerosols that are present in the stratosphere. Relatively inactive chlorine?containing molecules are chemically changed on surfaces of PSC particles. After the return of sun in the Spring activated chlorine will produce large ozone losses leading to the formation of an ozone hole. Despite the importance of PSCs for the ozone chemistry in the polar stratosphere, hardly any chemical analysis is available although composition and phase (liquid or solid) are important for the chlorine activation process. The fragile particles are very sensitive to changes in temperatures and thus a transfer into an instrument is difficult.

On 25 January 2000, instruments of European and American scientists were launched onboard a balloon gondola from Kiruna/Sweden to perform a comprehensive investigation of PSCs. In 20?23 km altitude clouds were repeatedly encountered. The main instrument on the gondola was a particle composition analyzer developed at the Max-Planck-Institute for Nuclear Physics, Heidelberg, that transfers the particles without alterations to a mass spectrometer for molecular analysis. Days before the balloon flight a cold region had developed above northern Scandinavia in which PSCs were formed.

During the 3-hour flight, nitric acid trihydrate crystals (NAT crystals) were identified for the first time. These particles contain three molecules of water and one molecule of nitric acid and can exist in the atmosphere up to 7° above the ice point. Besides NAT particles, liquid aerosols were also identified and analyzed. Surprisingly, those were found at the lowest atmospheric temperatures encountered during the flight. Together with the other particle experiments from the USA, Italy, France, and Denmark details of physical and chemical particle parameters were measured never obtained before. It was found that the complexity of PSC particle formation has actually increased. It is presently not clear which processes will change liquid into solid (crystalline) particles and many small into a few large ones.

At the present time, two gondolas are again waiting in Kiruna for polar stratospheric clouds. Instruments on the gondola have been further improved and are extensively calibrated. The research conducted in past and present experiments was supported by the European Union and for our American partners by the National Science Foundation.
-end-
Figure: Balloon gondola before the flight in Kiruna, Sweden, on 25. Jan. 2 000 with instruments from 5 countries participating in a comprehensive investigation of polar stratospheric clouds (PSCs). The central instrument is a particle analyzer developed at the Max-Planck-Institute for Nuclear Physics, Heidelberg.

Max-Planck-Gesellschaft

Related Stratosphere Articles from Brightsurf:

International team tracks record-setting smoke cloud from Australian wildfires
Researchers with the University of Saskatchewan's Institute of Space and Atmospheric Studies are part of a global team that has found that the smoke cloud pushed into the stratosphere by last winter's Australian wildfires was three times larger than anything previously recorded.

Iodine may slow ozone layer recovery
Air pollution and iodine from the ocean contribute to damage of Earth's ozone layer.

Snowmageddon warnings in North America come from tropics more than Arctic stratosphere
Scientists conducted the first ever study to identify how the four main winter weather patterns in the US and Canada behave depending on the strength of the stratospheric polar vortex.

Reevaluating the impacts of smoke plumes aloft, based on the 2017 Pacific Northwest wildfires
Extensive wildfires in the Pacific Northwest in the summer of 2017 unleashed a vast plume of smoke that ascended high into the stratosphere, persisted for more than eight months and provided researchers a rare opportunity to evaluate current models of smoke ascent.

Persistent plume
Thunderstorms generated by a group of giant wildfires in 2017 injected a small volcano's worth of aerosol into the stratosphere, creating a smoke plume that lasted for almost nine months.

Super volcanic eruptions interrupt ozone recovery
Strong volcanic eruptions, especially when a super volcano erupts, will have a strong impact on ozone, and might interrupt the ozone recovery processes.

2018's biggest volcanic eruption of sulfur dioxide
The Manaro Voui volcano on the island of Ambae in the nation of Vanuatu in the South Pacific Ocean made the 2018 record books.

Extratropical volcanoes influence climate more than assumed
The eruption of Mount Pinatubo in 1991 had a significant impact on climate, decreasing global mean temperature by about 0.5°C.

The ozone layer continues to thin
The vital ozone layer has continued to deplete in recent years over the densely populated mid-latitudes and tropics, while it is recovering at the poles.

Ozone at lower latitudes is not recovering, despite Antarctic ozone hole healing
The ozone layer -- which protects us from harmful ultraviolet radiation -- is recovering at the poles, but unexpected decreases in part of the atmosphere may be preventing recovery at lower latitudes.

Read More: Stratosphere News and Stratosphere Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.