Publication

New Particle Formation Events Can Reduce Cloud Droplets in Boundary Layer Clouds at the Continental Scale

Athanasios Nenes, Spyros Pandis
2024
Journal Articles

Abstract

New particle formation (NPF) substantially contributes to global cloud condensation nuclei (CCN), and their climate impacts. Individual NPF events are also thought to increase local CCN, cloud droplet number (CDN), and cloud albedo. High resolution simulations however go against the latter, showing that radiatively important stratiform clouds can experience a systematic and substantial decrease in CDN during and after NPF events. CDN drops because particles too small to act as CCN uptake condensable material, and stunt the growth of particles that would otherwise form droplets. Convective clouds however experience modest increases in CDN-consistent with established views on the NPF-cloud link. Together, these results reshape our conceptual understanding of NPF impacts on clouds, as the newly discovered duality of responses would drive cloud systems in a fundamentally different manner than thought.|Most studies assume that cloud condensation nuclei (CCN) changes from new particle formation (NPF) events directly reflect cloud droplet number (CDN) responses in clouds and ignore the growth of pre-existing particles and their contribution to CCN. High resolution state-of-the-art simulations over Europe portray that while convective clouds experience modest increases in CDN, the radiatively important stratiform clouds may present a systematic and substantial decrease in droplet number during and after new particle formation (NPF) events. Consequently, it is evident that NPF exhibits a duality in response-which depending on the local conditions may vitally change the manner in which cloud systems may respond.|New particle formation (NPF) events have always been thought to increase the concentration of particles that form cloud droplets thus always lead to climate cooling tau hrough high resolution modeling it is showed that stratiform clouds influenced by NPF events may experience systematic reductions in droplet leading to local warming from reductions in cloud albedo, while droplet number is always enhanced in convective cloudsThese effects combined could bear important impacts on cloud properties and structure following NPF events

Official source

Athanasios Nenes, Spyros Pandis
2024
Journal Articles

Abstract

Official source

Related concepts (20)

Cloud condensation nuclei

Cloud condensation nuclei (CCNs), also known as cloud seeds, are small particles typically 0.2 μm, or one hundredth the size of a cloud droplet. CCNs are a unique subset of aerosols in the atmosphere on which water vapour condenses. This can affect the radiative properties of clouds and the overall atmosphere. Water requires a non-gaseous surface to make the transition from a vapour to a liquid; this process is called condensation. In the atmosphere of Earth, this surface presents itself as tiny solid or liquid particles called CCNs.

Cloud

In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature.

Cloud physics

Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of atmospheric clouds. These aerosols are found in the troposphere, stratosphere, and mesosphere, which collectively make up the greatest part of the homosphere. Clouds consist of microscopic droplets of liquid water (warm clouds), tiny crystals of ice (cold clouds), or both (mixed phase clouds), along with microscopic particles of dust, smoke, or other matter, known as condensation nuclei.

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Copernicus GmbH2024