Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?

Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur GraphSearch.

Découvrez-en plus sur les applications Graph.

Graph
Search

fr|en

Se Connecter

Concept

Noyau de condensation

Résumé

thumb|Pollution atmosphérique causée par des aérosols sur le nord du sous-continent indien. Un noyau de condensation est une particule hygroscopique flottant dans la troposphère et sur laquelle la vapeur d'eau contenue dans l'air se déposera pour former une gouttelette. En effet, dans de l'air pur, où il n'y aurait aucune poussière ou ion, il faudrait atteindre une sursaturation de 500 % avant que la vapeur d'eau ne forme des gouttes à cause de la tension superficielle de l'eau à . Ces aérosols, typiquement de l'ordre de à quelques micromètres, favorisent donc la formation des nuages et des précipitations, d'où l'acronyme parfois employé NCN pour noyau de condensation de nuage. Granulométrie et composition vignette|Fonctions et devenirs des composés organiques volatils (COV) à trois niveaux : communauté, écosystème/biome et atmosphère-biosphère. Il existe trois classes de noyaux de condensation : les noyaux de Aitken (0,005 à ), les gros noyaux (0,1 à ) et les noyaux géants

Source officielle

https://fr.wikipedia.org/wiki/Noyau_de_condensation

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (100)

Chargement

Afficher plus

Publications associées

Chargement

Personnes associées (7)

Personnes associées

Chargement

Unités associées (4)

Unités associées

Chargement

Concepts associés (32)

Un nuage est en météorologie une masse visible constituée initialement d'une grande quantité de gouttelettes d’eau (parfois de cristaux de glace associés à des aérosols chimiques ou des minéraux) en

vignette|redresse=1.35|Températures moyennes de l'air en surface de 2011 à 2020 par rapport à une moyenne de référence de 1951 à 1980. vignette|redresse=1.35|Température observée par la NASA par rappo

Les particules en suspension sont toutes les particules (solides ou en aérosols) portées par l'eau ou par l'air, quantifiables par filtration ou par d'autres procédés physiques. Les matières partic

Afficher plus

Concepts associés

Chargement

Cours associés (5)

Cours associés

Chargement

Séances de cours associées (7)

Séances de cours associées

Chargement

Publications associées (100)

On the drivers of droplet variability in Alpine mixed-phase clouds

Alexis Berne, Paraskevi Georgakaki, Maxime Hervo, Athanasios Nenes, Jörg Wieder

Droplet formation provides a direct microphysical link between aerosols and clouds (liquid or mixed-phase), and its adequate description poses a major challenge for any atmospheric model. Observations are critical for evaluating and constraining the process. To this end, aerosol size distributions, cloud condensation nuclei (CCN), hygroscopicity, and lidar-derived vertical velocities were observed in alpine mixed-phase clouds during the Role of Aerosols and Clouds Enhanced by Topography on Snow (RACLETS) field campaign in the Davos, Switzerland, region during February and March 2019. Data from the mountain-top site of Weissfluhjoch (WFJ) and the valley site of Davos Wolfgang are studied. These observations are coupled with a state-of-the-art droplet activation parameterization to investigate the aerosol–cloud droplet link in mixed-phase clouds. The mean CCN-derived hygroscopicity parameter, κ, at WFJ ranges between 0.2–0.3, consistent with expectations for continental aerosols. κ tends to decrease with size, possibly from an enrichment in organic material associated with the vertical transport of fresh ultrafine particle emissions (likely from biomass burning) from the valley floor in Davos. The parameterization provides a droplet number that agrees with observations to within ∼ 25 %. We also find that the susceptibility of droplet formation to aerosol concentration and vertical velocity variations can be appropriately described as a function of the standard deviation of the distribution of updraft velocities, σw, as the droplet number never exceeds a characteristic limit, termed the “limiting droplet number”, of ∼ 150–550 cm−3, which depends solely on σw. We also show that high aerosol levels in the valley, most likely from anthropogenic activities, increase the cloud droplet number, reduce cloud supersaturation (

2021

Chargement

In-Situ Observations Of Aerosol Hygroscopicity And Cloud Droplet Formation In Ny-Ålesund, Svalbard, During Fall 2019 And Spring 2020

Paraskevi Georgakaki, Ghislain Gilles Jean-Michel Motos, Athanasios Nenes, Jörg Wieder

The Arctic region suffers an extreme vulnerability to climate change, with an increase in surface air temperatures that have reached twice the global rate during several decades (McBean et al., 2005). The role of clouds, and in particular low-levels clouds and fog, in this arctic amplification by regulating the energy transport from and to space has recently gained interest among the scientific community. The NASCENT 2019-2020 campaign (Ny-Ålesund AeroSol Cloud ExperimeNT) based in Ny-Ålesund, Svalbard (79º North) aimed at studying the microphysical and chemical properties of low-level clouds using measurements both at the sea level and at the Zeppelin station (475 m a.s.l.). First results using a scanning mobility particle sizer (SMPS) and a cloud condensation nuclei counter (CCNC) confirmed that aerosol concentrations in the range 10 < Dpart [nm] < 500 were approximatively 4-5 times higher during the months of Spring 2021 compared to those of Fall 2020. In addition, we found filterpack-derived values of the aerosol hygroscopic parameter κ around 0.7. Combined with temperature and pressure data, these results were used as input parameters for the Morales Betancourt and Nenes (2014) parameterization in order to investigate the susceptibility of droplet formation, which has recently been shown to be highly dependent on aerosol levels in European alpine valleys (Georgakaki et al., 2021). We found strong variations between the Fall to Winter months, known for pristine-like conditions, and the higher particle concentrations generally found in Spring, known as the arctic haze. Specifically, droplet formation was always limited by the low aerosol concentrations in Fall/Winter, whereas updraft-limited cloud formation occurred in Spring. Reviewing relevant literature tells that the relationship between the limiting droplet number concentration and the updraft velocity during NASCENT agrees with that of various locations worldwide, which tends to confirm the universality of this relationship. Georgakaki, P., Bougiatioti, A., Wieder, J., Mignani, C., Ramelli, F., Kanji, Z. A., Henneberger, J., Hervo, M., Berne, A., Lohmann, U., and Nenes, A.: On the drivers of droplet variability in alpine mixed-phase clouds, 21, 10993–11012, https://doi.org/10.5194/acp-21-10993-2021, 2021. McBean, G., Alekseev, G., Chen, D., Førland, E., Fyfe, Groisman, J., P. Y., King, R., Melling, H., Voseand, R., Whitfield, P. H.: Arctic climate: past and present. Arctic Climate Impacts Assessment (ACIA), C. Symon, L. Arris and B. Heal, Eds., Cambridge University Press, Cambridge, 21-60, 2005. Morales Betancourt, R. and Nenes, A.: Droplet activation parameterization: the population-splitting concept revisited, 7, 2345–2357, https://doi.org/10.5194/gmd-7-2345-2014, 2014.

2021

Chargement

, , ,

The Arctic region suffers an extreme vulnerability to climate change, with an increase in surface air temperatures that have reached twice the global rate during several decades (McBean et al., 2005). The role of clouds, and in particular low-levels clouds and fog, in this arctic amplification by regulating the energy transport from and to space has recently gained interest among the scientific community. The NASCENT 2019-2020 campaign (Ny-Ålesund AeroSol Cloud ExperimeNT) based in Ny-Ålesund, Svalbard (79º North) aimed at studying the microphysical and chemical properties of low-level clouds using measurements both at the sea level and at the Zeppelin station (475 m a.s.l.). Specifically, the susceptibility of droplet formation, which has recently been shown to be highly dependent on aerosol levels in European alpine valleys (Georgakaki et al., under review), could strongly vary between the fall to winter months, with pristine-like conditions, and the higher particle concentrations generally found in spring, known as the arctic haze. First results using a scanning mobility particle sizer (SMPS) and a cloud condensation nuclei counter (CCNC) confirmed that aerosol concentrations in the range 10 < Dpart [nm] < 500 were approximatively 4-5 times higher during the months of spring 2021 compared to those of fall 2020. In addition, we found relatively low values of the aerosol hygroscopic parameter κ, generally below 0.3, consistently with previous studies in the arctic region (Moore et al., 2011). Georgakaki, P., Bougiatioti, A., Wieder, J., Mignani, C., Kanji, Z. A., Henneberger, J., Hervo, M., Berne, A. and Nenes, A.: On the drivers of droplet variability in Alpine mixed-phase clouds, , 34, under review. McBean, G., Alekseev, G., Chen, D., Førland, E., Fyfe, Groisman, J., P. Y., King, R., Melling, H., Voseand, R., Whitfield, P. H.: Arctic climate: past and present. Arctic Climate Impacts Assessment (ACIA), C. Symon, L. Arris and B. Heal, Eds., Cambridge University Press, Cambridge, 21-60, 2005. Moore, R. H., Bahreini, R., Brock, C. A., Froyd, K. D., Cozic, J., Holloway, J. S., Middlebrook, A. M., Murphy, D. M. and Nenes, A.: Hygroscopicity and composition of Alaskan Arctic CCN during April 2008, Atmospheric Chemistry and Physics, 11(22), 11807–11825, https://doi.org/10.5194/acp-11-11807-2011, 2011.

2021

Chargement

Afficher plus

On the drivers of droplet variability in Alpine mixed-phase clouds

Alexis Berne, Paraskevi Georgakaki, Maxime Hervo, Athanasios Nenes, Jörg Wieder

2021

In-Situ Observations Of Aerosol Hygroscopicity And Cloud Droplet Formation In Ny-Ålesund, Svalbard, During Fall 2019 And Spring 2020

Paraskevi Georgakaki, Ghislain Gilles Jean-Michel Motos, Athanasios Nenes, Jörg Wieder

2021

, , ,

The Arctic region suffers an extreme vulnerability to climate change, with an increase in surface air temperatures that have reached twice the global rate during several decades (McBean et al., 2005). The role of clouds, and in particular low-levels clouds and fog, in this arctic amplification by regulating the energy transport from and to space has recently gained interest among the scientific community. The NASCENT 2019-2020 campaign (Ny-Ålesund AeroSol Cloud ExperimeNT) based in Ny-Ålesund, Svalbard (79º North) aimed at studying the microphysical and chemical properties of low-level clouds using measurements both at the sea level and at the Zeppelin station (475 m a.s.l.). Specifically, the susceptibility of droplet formation, which has recently been shown to be highly dependent on aerosol levels in European alpine valleys (Georgakaki et al., under review), could strongly vary between the fall to winter months, with pristine-like conditions, and the higher particle concentrations generally found in spring, known as the arctic haze. First results using a scanning mobility particle sizer (SMPS) and a cloud condensation nuclei counter (CCNC) confirmed that aerosol concentrations in the range 10 < Dpart [nm] < 500 were approximatively 4-5 times higher during the months of spring 2021 compared to those of fall 2020. In addition, we found relatively low values of the aerosol hygroscopic parameter κ, generally below 0.3, consistently with previous studies in the arctic region (Moore et al., 2011). Georgakaki, P., Bougiatioti, A., Wieder, J., Mignani, C., Kanji, Z. A., Henneberger, J., Hervo, M., Berne, A. and Nenes, A.: On the drivers of droplet variability in Alpine mixed-phase clouds, , 34, under review. McBean, G., Alekseev, G., Chen, D., Førland, E., Fyfe, Groisman, J., P. Y., King, R., Melling, H., Voseand, R., Whitfield, P. H.: Arctic climate: past and present. Arctic Climate Impacts Assessment (ACIA), C. Symon, L. Arris and B. Heal, Eds., Cambridge University Press, Cambridge, 21-60, 2005. Moore, R. H., Bahreini, R., Brock, C. A., Froyd, K. D., Cozic, J., Holloway, J. S., Middlebrook, A. M., Murphy, D. M. and Nenes, A.: Hygroscopicity and composition of Alaskan Arctic CCN during April 2008, Atmospheric Chemistry and Physics, 11(22), 11807–11825, https://doi.org/10.5194/acp-11-11807-2011, 2011.

2021