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Accueil du site → Doctorat → États-Unis → 2005 → Sensitivity of diurnal change and synoptic features to dust aerosols over the region of Saudi Arabia

FLORIDA STATE UNIVERSITY (2005)

Sensitivity of diurnal change and synoptic features to dust aerosols over the region of Saudi Arabia

MOHALFI, SAAD MOHAMED SAID

Titre : Sensitivity of diurnal change and synoptic features to dust aerosols over the region of Saudi Arabia

Auteur : MOHALFI, SAAD MOHAMED SAID

Université de soutenance : FLORIDA STATE UNIVERSITY

Grade : Doctor of Philosophy (PhD) 2005

Résumé
A two-stream multiple-scattering model based on the Delta-Eddington approximation, has been incorporated into the FSU limited area model for computing the shortwave radiative fluxes for dust aerosols over the region of Saudi Arabia. The period of 26 June to 1 July, 1979, has been selected as the period of concentration for this study. This was during the late June, 1979 extensive dust storm outbreak. In this study, the radiative dust properties are determined based upon the findings of field experiments corresponding to different categories of dustiness and horizontal visibility. Satellite data and visibility were used to determine the intensity of dust. The dust layer (DL) structure and behavior have been analyzed and have been used to locate the dust boundaries and thicknesses. A two parallel forecast of the FSU regional model has been performed. One of these includes the radiative transfer of dust aerosols in its radiation scheme. Both models are initiated with the FGGE IIIb data set, which has been analyzed at the ECMWF. A comparison between the two experiments shows that the absence of dust aerosol radiative heat will weaken the heat low over the region of Saudi Arabia. Furthermore, the radiative heat of the heavy dust, concentrated at the low level during the dust outbreak episode, protects the heat low from any further destruction due to cold advection and strong wind. A significant improvement in the diurnal cycle of temperature at the middle level occurred when the dust aerosols were introduced into the level. The presence of dust aerosols over the sea surface has been found to weaken the sea breeze circulation, but when the DL base is lifted to 850 mb or above, the model simulated a diurnal cycle of the sea breeze. The extension of the DL over the Arabian Sea was found to warm the middle level in the vicinity of the DL and cool the layer below the DL. It also intensifies the inversion above the monsoon flow.

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