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Impact Des Aerosols Sur Le Cycle De Vie Du Brouillard De Vie Du Brouillard
| Content Provider | Semantic Scholar |
|---|---|
| Author | Rangognio, Jérôme Bergot, Thierry Tulet, Pierre |
| Copyright Year | 2014 |
| Abstract | The role of the atmospheric particles in cloud droplets formation was the object of numerous works, the point of view experimental as numerical. This work is interested in the radiation fog. One of the particularities of radiation fog is its development within the surface boundary layer, directly in contact with the ground, where aerosols concentrations are the highest. To understand the influence of these particles on the fog life cycle, two fields experiments ParisFOG and ToulouseFOG were realized. After a state of general art on the characteristics of the atmospheric particles, several cases of radiation fogs are presented, by insisting more particularly on the properties of aerosols and cloud droplets measured during these two fields experiments. It seems generally very difficult to feature the physical explications based only on the observations. To achieve this objectif, a series of 1D simulations were preformed with the Meso-NH numerical mesoscale model, in which the ORILAM aerosol scheme was coupled with the two-moment microphysical scheme. The activation scheme used was taken from the work of Abdul-Razzak et Ghan (2004). This parameterization allows to take into account the observed aerosol chemical composition and size distribution. In this approach, the necessity of a joint initiative between the observation and the modelling is clearly appeared. "Off-line" sensitivity analysis of CCN (Cloud Condensation Nuclei) were performed on number, median diameter and chemical compounds of aerosols using only the activation scheme of Abdul-Razzak et Ghan (2004). During this "off-line" study, the interactions with the other physical processes were not taken into account. Different regimes of CCN activation and a critical value of aerosol number concentration were found. This critical aerosol number corresponds to the maximum of activated cloud droplets for a given cooling rate and given aerosol chemical properties. 1D simulations successfully reproduced the observed temporal evolution of the fog layer during an intensive observation period of the field experiment ParisFOG. These simulations confirmed that the aerosol particle number concentration is a key parameter for the accurate prediction of the microphysical properties of a fog layer and also influences the vertical development of fog. The important of the interaction between microphysical and radiative processes is illustrated, showing how the life cycle of fog is determined by the CCN number concentration and chemical properties. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://thesesups.ups-tlse.fr/773/1/Rangognio_Jerome.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
