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Comparison of atmospheric properties retrieved from MERIS and obtained from modelling studies

Dina Santos(1), Miguel Potes(1), Maria João Costa(2), Rui Salgado(2) and Ana Maria Silva(2)

(1) Évora Geophysics Centre, Rua Romão Ramalho, 59, 7000 Évora, Portugal
(2) Evora Geophysics Centre, Physics Department, Rua Romão Ramalho, 59, 7000 Évora, Portugal


Clouds and aerosols are the major factors regulating the Earth radiation budget. These atmospheric constituents strongly modulate the energy balance of the Earth through absorption and scattering of solar radiation and absorption and emission of terrestrial radiation. Although the importance of clouds and aerosols is extensively recognized, their impact is associated with great uncertainties due to the complexity and space-time variation of the phenomena. Moreover, aerosols may also modify cloud properties by varying the number concentration of cloud droplets, changing both cloud optical depth and cloud life time. However, the knowledge of aerosols effects on clouds is still very limited, therefore special attention has been dedicated to these studies in the last years. The study and evaluation of cloud and aerosol effects may be done through the use of atmospheric models. However, cloud and aerosol properties must be reasonably represented in the models, in order to reproduce in the best possible way the actual atmospheric conditions. This work aims at comparing several modelled cloud and aerosol properties, with the Medium Resolution Imaging Spectrometer (MERIS) Level 2 product that contains quantities such as aerosol optical thickness, cloud fraction, cloud effective radius. The evolution of clouds and aerosols during some recent dust events are simulated using the mesoscale nonhydrostatic atmospheric model (MesoNH), over the Iberian Peninsula and nearby Atlantic Ocean. MesoNH can simulate atmospheric circulations from small to synoptic scales with horizontal resolutions ranging from a few meters to several tens of kilometres; it includes schemes for convection, cloud microphysics (taking into account six water species) and the ECMWF radiation radiative transfer model. Surface dust emissions are computed using the Dust Entrainment and Deposition Model (DEAD) included in the MesoNH.