In the current study, the cloud base height obtained from the ceilometer measurements, in Evora (south of Portugal), are
compared with the results obtained from atmospheric modelling. The atmospheric model adopted is the nonhydrostatic
MesoNH model, initiated and forced by ECMWF (European Centre for Medium-Range weather Forecasts) analyses.
Also the simulated cloud depth results are presented. The availability of mesoscale modelling for the region, as well as
the cloud local vertical distributions obtained from the ceilometer, provide a good opportunity to compare cloud base
height and estimate the errors associated. From the obtained results it is possible to observe that the simulated cloud base
height values are in good agreement with the correspondent values obtained from the ceilometer measurements.
The aim of this work is the study of the Saharan desert dust storms effects on clouds properties and respective radiative
forcing during a strong desert dust transport that occurred in 27, 28 and 29 May 2006. This is done by examining the
results obtained from a mesoscale atmospheric model (MesoNH), over Portugal area and nearby Atlantic Ocean.
The assessment of the aerosol properties provides information on the altitude of the aerosol layers and the determination
of the cloud properties, influenced by the presence of desert dust aerosol, gives the information about the possible
modifications that the cloud may suffer when they develop in an atmosphere where desert dust aerosols are present. The
cloud radiative forcing (CRF) at the top of the atmosphere (TOA) is also estimated. The CRF at the TOA, in a dust free
atmosphere, present lower values when compared with the TOA CRF over the regions where dust aerosols are present.
The present work aims to investigate the effects of Saharan desert dust storms on cloud properties and respective
radiative forcing over the South of Portugal and nearby Atlantic Ocean, for a case study that occurred between 26 and 29
May 2006, using the MODerate Resolution Imaging Spectroradiometer (MODIS) satellite data.
The determination of cloud properties in different regions subject to the presence of dust aerosols provides information
on the possible alterations that these clouds may suffer due to the presence of an aerosol layer. Cloud effective radius,
optical depth and water path retrieved values are considerably smaller for clouds developing in a dusty atmosphere than
for clouds in a dust-free atmosphere. Due to these changes it was also possible to observe that the instantaneous cloud
radiative forcing (ICRF) values at the top of the atmosphere (TOA) and at the surface are lower when dust aerosols are
not present.
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