Skip to Main content Skip to Navigation
Theses

Composition chimique détaillée d'un nuage mixte. Etude in situ des mécanismes d'incorporation d'acides forts et faibles dans la précipitation solide.

Abstract : Ice is common in clouds, even at low altitude. Nevertheless, the impact of the ice phase on tropospheric chemistry is poorly known and cannot be studied without precise understanding of the phase partitionning of gases in mixed clouds. In order to study this partition, supercooled water, precipitating ice, interstitial gases and aerosol have been collected at the Puy de Dôme' s observatory in mixed clouds whose liquid water and ice water content was measured at the same time. Henry's law fails to describe the uptake of gases by supercooled droplets. Deviations from the equilibrium were higher for the most soluble species (HCI et HN03) at higher pH. Those deviations correlate with the solution' s pH and are not affected by the presence of ice. They also are too important to be attributed solely to mass transfert limitations. Shock-freezing of supercooled droplets at their impaction on ice crystals induces losses of a large fraction of soluble gases (S02, and to a lesser extent, acetic acid). Microphysical characterisation of the cloud enabled theoretical evaluation of the incloud scavenging of interstitial aerosol by snow, as weIl as of its rimed mass fraction. The rime fraction in snow was also estimated by comparing the concentrations in snow and water for species characterizing cloud condensation nuclei. Both estimations agree and, since in-cloud scavenging of aerosol prooved to be negligible, we could distinguish between riming and solubilisation of gases in the observed concentrations in snow. Strong acids appear to be mainly incorporated in ice through riming, whereas direct solubilisation of gases can be important for weak acids. This solubilization is depending on physical characteristics of the cloud.
Document type :
Theses
Complete list of metadata

https://tel.archives-ouvertes.fr/tel-00704919
Contributor : Pascale Talour <>
Submitted on : Wednesday, June 6, 2012 - 3:10:26 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Friday, September 7, 2012 - 2:35:36 AM

Identifiers

  • HAL Id : tel-00704919, version 1

Collections

Citation

Didier Voisin. Composition chimique détaillée d'un nuage mixte. Etude in situ des mécanismes d'incorporation d'acides forts et faibles dans la précipitation solide.. Météorologie. Université Joseph-Fourier - Grenoble I, 1998. Français. ⟨tel-00704919⟩

Share

Metrics

Record views

1640

Files downloads

359