Turbulence creates ice in clouds

November 08, 2019

Leipzig. Vertical air motions increase ice formation in mixed-phase clouds. This correlation was predicted theoretically for a long time, but could now be observed for the first time in nature. This result was published by a team from Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig in npj Climate and Atmospheric Science, an Open Access journal published by Nature Research. Using laser and radar equipment, the team measured the vertical air velocity and ice formation in thin mixed-phase clouds. Such clouds contain ice particles, water vapour as well as supercooled liquid droplets. The results from Leipzig could help to map an important part of the water cycle better in the weather and climate models in the future by ice formation in clouds.

The formation of ice in clouds is a core element of the water cycle on Earth. It is usually difficult to isolate the ice formation process in order to study it individually because the interaction of aerosol particles, air motion and microphysical processes in clouds is too complex. Nevertheless, it is necessary to understand these processes in detail in order to better map this mechanism in weather and climate models.

The cloud researchers concentrated on a less spectacular and therefore less considered form of clouds in order to exclude other processes than primary ice formation. They investigated large cloud fields at an altitude of about 2 to 8 kilometres with a vertical extent of only 100 to 200 metres and contained extremely little ice in the range of micrograms per cubic meter. Such thin cloudsallow both ice to be detected with a cloud radar and the vertical air movement with a Doppler lidar, as the laser beam can still penetrate the clouds. Both lidar and radar instruments were therefore necessary to investigate the turbulence and ice formation in these clouds above Leipzig from the ground. "The effect only became visible when we observed the ice directly below the clouds' top layer. Our findings enable for the first time quantitative and well constraint insights into the relationship between turbulence and ice formation in the atmosphere. The stronger a cloud is 'shaken' by vertical air motions, the more ice falls out of it," reports Dr Johannes Bühl of TROPOS. This correlation was measured for clouds colder than -12 °C. Next, the remote sensing scientists want to explore the influence of aerosols by taking a closer look at the beginning (ice nucleation) and end (precipitation of ice particles) of the ice formation process.

Ice formation in clouds is an important process in the atmosphere, because without this ice practically no precipitation would fall from clouds in the middle latitudes of the Earth. As far-reaching as these processes may be, many details have not yet been sufficiently understood and are therefore not taken into account in the weather and climate models. Tilo Arnhold
-end-
Publication:

Bühl, Johannes; Seifert, Patric; Engelmann, Ronny and Ansmann, Albert (2019): Impact of vertical air motions on ice formation rate in mixed-phase cloud layers. npj Climate and Atmospheric Science volume 2, Article number: 36 (2019). DOI: 10.1038/s41612-019-0092-6.

https://doi.org/10.1038/s41612-019-0092-6

The study was funded by the European Union under the Seventh Framework Programme (ACTRIS / 262254 and BACCHUS / 603445) and the German Research Foundation (DFG; UNDINE / 162311106).

Links:

The Leipzig Aerosol and Cloud Remote Observations System LACROS

https://www.tropos.de/en/research/projects-infrastructures-technology/coordinated-observations-and-networks/lacros

Current data from LACROS:

http://lacros.rsd.tropos.de/

CLOUDNET:

https://www.tropos.de/en/research/projects-infrastructures-technology/coordinated-observations-and-networks/cloudnet

Contacts:

Dr Johannes Bühl, Dr Patric Seifert, Dr Ronny Engelmann
Scientific staff, Department „Remote Sensing of Atmospheric Processes" at the Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
Phone +49-341-2717-7312, -7080, -7315

https://www.tropos.de/en/institute/about-us/employees/johannes-buehl
https://www.tropos.de/en/institute/about-us/employees/patric-seifert
https://www.tropos.de/en/institute/about-us/employees/ronny-engelmann

and

Dr Albert Ansmann
Leader of the Working Group Ground Based Remote Sensing, Department „Remote Sensing of Atmospheric Processes" at the Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
Phone: +49-341-2717-7064
https://www.tropos.de/en/institute/about-us/employees/albert-ansmann

or

Tilo Arnhold
Public Relations at the Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
Phone: +49-341-2717-7189
https://www.tropos.de/en/current-issues/press-releases

Leibniz Institute for Tropospheric Research (TROPOS)

Related Climate Models Articles from Brightsurf:

Polar ice, atmospheric water vapor biggest drivers of variation among climate models
A Florida State University researcher is part of a team that has found varying projections on global warming trends put forth by climate change scientists can be explained by differing models' predictions regarding ice loss and atmospheric water vapor.

Revising climate models with new aerosol field data
Advanced field measurements of how quickly aerosol particles are pulled out of the air can help improve climate predictions - and air quality forecasts.

Simpler models may be better for determining some climate risk
Typically, computer models of climate become more and more complex as researchers strive to capture more details of our Earth's system, but according to a team of Penn State researchers, to assess risks, less complex models, with their ability to better sample uncertainties, may be a better choice.

Atmospheric scientists study fires to resolve ice question in climate models
Black carbon from fires is an important short-term climate driver because it can affect the formation and composition of clouds.

New soil models may ease atmospheric CO2, climate change
To remove carbon dioxide from the Earth's atmosphere in an effort to slow climate change, scientists must get their hands dirty and peek underground.

Patterns in permafrost soils could help climate change models
A team of scientists spent the past four summers measuring permafrost soils across a 5,000 square-mile swath of Alaska's North Slope.

Latest climate models show more intense droughts to come
An analysis of new climate model projections by Australian researchers from the ARC Centre of Excellence for Climate Extremes shows southwestern Australia and parts of southern Australia will see longer and more intense droughts due to a lack of rainfall caused by climate change.

Some of the latest climate models provide unrealistically high projections of future warming
A new study from University of Michigan climate researchers concludes that some of the latest-generation climate models may be overly sensitive to carbon dioxide increases and therefore project future warming that is unrealistically high.

A Europe covered in grasslands or forests: innovation and research on climate models
An experiment to better understand how atmospheric variables respond to land use changes.

How tiny water droplets form can have a big impact on climate models
Droplets and bubbles are formed nearly everywhere, from boiling our morning coffee, to complex industrial processes and even volcanic eruptions.

Read More: Climate Models News and Climate Models 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.