Open AccessModeling of Saharan dust outbreaks over the Mediterranean by RegCM3: case studies
Author(s) -
M. Santese,
M. R. Perrone,
A. S. Zakey,
F. De Tomasi,
Filippo Giorgi
Publication year - 2010
Publication title -
atmospheric chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.622
H-Index - 206
eISSN - 1680-7324
pISSN - 1680-7316
DOI - 10.5194/acp-10-133-2010
Subject(s) - radiative forcing , aerosol , radiative transfer , atmospheric sciences , environmental science , forcing (mathematics) , radiometer , mineral dust , climatology , aeronet , optical depth , atmospheric radiative transfer codes , climate model , earth's energy budget , meteorology , climate change , physics , radiation , remote sensing , geology , oceanography , quantum mechanics
The regional climate model RegCM3 coupled with a radiatively active aerosolmodel with online feedback is used to investigate direct and semi-directradiative aerosol effects over the Sahara and Europe in a test case of July 2003.The aerosol model includes dust particles in addition to sulfates,hydrophobic and hydrophilic black carbon and organic carbon. The role of theaerosol online feedback on the radiation budget and the direct radiativeforcing (short-wave and long-wave) by dust particles are investigated byintercomparing results from three experiments: REF, including allinteractive aerosol components, Exp1, not accounting for the aerosolradiative feedback, and Exp2 not accounting for desert dust particles. Thecomparison of results in the REF experiment with satellite observations,sun/sky radiometer measurements, and lidar profiles at selected CentralMediterranean sites reveals that the spatio-temporal evolution of theaerosol optical depth is reasonably well reproduced by the model during theentire month of July. Results for the dust outbreaks of 17 and 24 July,averaged over the simulation domain, show that the daily-mean SW directradiative forcing by all particles is −24 Wm−2 and −3.4 Wm−2 on17 July and −25 Wm−2 and −3.5 Wm−2 on 24 July at the surface andtop of the atmosphere, respectively. This is partially offset by the LWdirect radiative forcing, which is 7.6 Wm−2 and 1.9 Wm−2 on 17 July and8.4 Wm−2 and 1.9 Wm−2 on 24 July at the surface and topof the atmosphere, respectively. Hence, the daily-mean SW forcing is offsetby the LW forcing of ~30% at the surface and of ~50% atthe ToA. It is also shown that atmospheric dynamics and hence dustproduction and advection processes are dependent on the simulationassumptions and may significantly change within few tens of kilometers. Thecomparison of REF and Exp1 shows that the aerosol online feedback on theradiation budget decreases the domain-average daily-mean value of the 2 m-temperature,aerosol column burden (CB), and short-wave (SW) atmosphericforcing by −0.52 °C, 14%, and 0.9%, respectively on 17 July and by−0.39 °C, 12% and 12%, respectively on 24 July. The comparison ofREF and Exp2 reveals that on 17 July, radiatively-active dust particlesdecrease the daily-mean 2 m-temperature averaged over the whole simulationdomain by 0.4% even if are responsible for 99.8% and 97% of thedaily-mean aerosol column burden and SW atmospheric forcing, respectively