Scientists accurately model the action of aerosols on clouds


Global climate is a tremendously complex phenomenon, and 
researchers are making painstaking progress, year by year, to 
try to develop ever more accurate models. Now, an international 
group including researchers from the Advanced Institute for 
Computational Science (AICS) in Japan, using the powerful K 
computer, have for the first time accurately calculated the 
effects of aerosols on clouds in a climate model.

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Aerosols play a key role in cloud formation, as they provide the 
"seeds" -called cloud condensation nuclei- that allow clouds to form 
and affect their life cycle. The water in the air condenses onto the 
tiny particles, and gradually grow into droplets and finally into 
raindrops that precipitate. The action of aerosols is an important 
element of research on climate change, as they partially counteract 
the heating action of greenhouse gases.
It was previously believed that increasing aerosol density would 
always lead to more clouds, but recent satellite observations showed 
that this is not necessarily true. It is now understood that, due to 
temperature differences between the top and bottom layers of clouds, 
there is a delicate balance of evaporation and condensation, with 
aerosols in the lower parts of the clouds promoting cloud formation, 
but those in the upper parts allowing the water to evaporate.
Previously, climate models were unable to model the response of these 
micro-processes within the clouds to aerosol variation, but using 
the  computer, the RIKEN-led group combined a model that simulates the 
entire global weather over a year, at a horizontal resolution of just 
14 kilometers, with a simulation of how the aerosols behave within 
clouds. Unlike conventional models, which show a uniform increase in 
clouds over the earth when there is an increase in aerosols, the 
high-resolution model, which takes into account the vertical processes 
inside clouds, accurately depicted how large areas experience a drop 
in cloud cover.
According to Yosuke Sato from the Computational Climate Science 
Research Team at RIKEN AICS and Nagoya University, "It was very 
gratifying to see that we could use a powerful supercomputer to 
accurately model the microphysics of clouds, giving a more accurate 
picture of how clouds and aerosol behave in the real world. In the 
future, we hope to use even more powerful computers to allow climate 
models to have more certainty in climate prediction."
The work, which was published in Nature Communications, was done by 
scientists from AICS in collaboration with researchers from Nagoya 
University, National Institute for Environmental Studies, Kyushu 
University, the University of Tokyo, and the Japan Aerospace 
Exploration Agency.


URL:
http://global.jaxa.jp/press/2018/03/20180313_aerosol.html

RIKEN
Nagoya University
Atmosphere and Ocean Research Institute The University of Tokyo
kyushu University
National Institute for Environmental Studies, Japan
National Research and Development Agency Japan Aerospace 
Exploration Agency (JAXA)