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Accueil du site → Doctorat → Allemagne → 2011 → Parametrization of relative humidity- and wavelength-dependent optical properties of mixed Saharan dust and marine aerosol

Universität Leipzig (2011)

Parametrization of relative humidity- and wavelength-dependent optical properties of mixed Saharan dust and marine aerosol

Schladitz, Alexander

Titre : Parametrization of relative humidity- and wavelength-dependent optical properties of mixed Saharan dust and marine aerosol

Auteur : Schladitz, Alexander

Université de soutenance : Universität Leipzig

Grade : Doctor rerum naturalium (Dr. rer. nat.) 2011

Résumé
Aerosol particles interact with sunlight through scattering and absorption and have therefore a direct radiative effect. Hygroscopic aerosol particles take up water and are able to grow in size below 100% relative humidity, which involves the change of optical properties and the direct radiative effect. The change of aerosol optical properties for aerosol mixtures under humidification is presently not well understood, especially for the largest particle sources worldwide. The present PhD-thesis quantifies wavelength- and humidity-dependent aerosol optical properties for a mixture of Saharan mineral dust and marine aerosol. For quantification, an aerosol model was developed, which based on in-situ measurements of microphysical and optical properties at Cape Verde. With this model, aerosol optical properties were calculated from the dry state up to 90% relative humidity. To validate the model, a measure of the total extenuated light from particles under ambient conditions was used. Finally, the humidity dependence of aerosol optical properties for marine aerosol, Saharan dust aerosol, and a mixture of both species was described by two empirical equations. With the wavelength of the incident visible solar radiation, relative humidity, and dry dust volume fraction, the humidity dependence of optical properties can be calculated from tabulated values. To calculate radiative effects, aerosol optical properties were used as input parameters for global circulation models including radiative transfer. Due to the complexity of aerosol related processes, they have been treated implicitly, meaning in parameterized form. For modelling purposes, the present PhD-thesis provides a solution to include humidity effects of aerosol optical properties.

Mots clés : Aerosole, optische Eigenschaften, Feuchteabhängigkeit, Staubpartikel, marine Partikel ; aerosols, optical properties, humidity dependence, dust particles, marine particles

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Page publiée le 18 décembre 2011, mise à jour le 16 janvier 2020