1,720,964 research outputs found
AERONET versus MODIS aerosol parameters at different spatial resolutions over South-East Italy
No full textAerosol parameters retrieved by Aerosol Robotic Network (AERONET) Sun photometer measurements at the Physics Department of Lecce's University (40°20′N, 18°6′E) are compared to similar Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved at different spatial resolutions colocated in space and time to contribute to the validation of MODIS aerosol products over southeast Italy and to investigate the correlation dependence on spatial resolution and identify regional biases of Lecce's AERONET data. In particular, MODIS aerosol optical depths retrieved at 550 nm over ocean and over land-ocean for window sizes of 50 × 50, 100 × 100, and 300 × 300 km2 centered on the AERONET monitoring site are correlated to AERONET aerosol optical depths colocated in time. It is shown that correlation factors of linear regressions span the 0.88–0.83 range and weakly tend to reduce with window size. In addition, MODIS aerosol optical depths meet expected uncertainties, and the percentage of data points within expected uncertainties is not affected by the window size. Slope and intercept values of linear regressions fitting over ocean aerosol optical depths are instead different than those fitting over land-ocean aerosol optical depths and are dependent on window size. The observed dependence is analyzed and discussed in the paper. Finally, it is shown that the paper's results can allow inferring that the tested AERONET aerosol parameters can be considered representative, at least, of a ∼300 × 300 km2 southeast Italy area centered on the Lecce's AERONET site
Moderate Resolution Imaging Spectroradiometer (MODIS) and Aerosol Robotic Network (AERONET) retrievals during dust outbreaks over the Mediterranean
No full textModerate Resolution Imaging Spectroradiometer (MODIS)–ocean aerosol products and corresponding Aerosol Robotic Network (AERONET) data retrieved during Sahara dust outbreaks that occurred over the central Mediterranean basin have been analyzed, to contribute to the validation of MODIS retrievals during dust-loading conditions. It is shown that MODIS aerosol optical depths (AODM) retrieved at 550 nm for window sizes of 50 × 50 km2 centered at different Mediterranean AERONET sites are in satisfactory accordance to corresponding AERONET optical depths (AODA) colocated in space and time: Correlation factor and slope of the linear regression are 0.86 and 1.04, respectively, and 42% of data points are within the prespecified accuracy range. However, the plot of the differences (AODM – AOD A ) versus AOD A has revealed that the differences (AODM – AOD A ) are almost positive and increase with AOD A , and has led assuming that MODIS overestimates AODs mainly during high dust load conditions. The comparison of MODIS-ocean and corresponding AERONET fine-mode fractions (η M and η A, respectively) colocated in space has revealed that the MODIS-ocean inversion algorithm overestimates the contribution of fine-mode particles for dust-dominated aerosols: (η M − η A) difference values vary within the 0.11–0.24 range. In addition, the comparison of MODIS-ocean and corresponding AERONET volume size distributions has revealed that the latter results are mainly due to the poor sensitivity of the MODIS-ocean inversion algorithm to the concentration of coarse-mode particles during dust outbreaks. The frequency distributions of MODIS fine and coarse volume modal radii are found to be rather close to corresponding AERONET frequency distributions.
Received 31 January 2007; accepted 30 May 2007
AEROSOL LOAD CHARACTERIZATION OVER SOUTH-EAST ITALY BY ONE YEAR OF AERONET SUN-PHOTOMETER MEASUREMENTS
No full textDaily averaged retrievals of AERONET sun photometer measurements from March 2003 to March 2004 are used to provide preliminary results on the characterization of aerosol properties and changes over south–east Italy (40°20′N, 18°6′E). It is shown that aerosol optical and microphysical properties and the dominating aerosol types depend on seasons. Aerosol-parameter frequency distributions reveal the presence of individual modes that lead to the assumption that moderately absorbing urban–industrial and marine-polluted aerosols dominate in spring–summer and autumn–winter, respectively. It is shown that aerosol optical depths (AODs), single scattering albedos (SSAs), and Angstrom coefficients (Å) of urban–industrial (spring–summer) aerosols are characterized by lognormal distributions with peak values of 0.20±0.03, 0.94±0.01, and 1.58±0.03, respectively. On the contrary AOD, SSA and Å values of maritime-polluted (autumn–winter) aerosols are characterized by lognormal distributions with peak values of 0.049±0.008, 0.974±0.003, and 0.7±0.1, respectively. It is also shown that the frequency distribution of real n and imaginary k refractive indices permits inference of the dominant aerosol constituents: sea-salt, water soluble, soot, and mineral particles.
Finally, it is shown that dust outbreaks do not significantly affect the seasonal evolution of aerosol parameters, and that sunphotometry retrievals along dust events are in satisfactory accord with experimental findings indicating that moderately-absorbing (0.005≤k≤0.05) dust particles with a high content of illite are mainly advected over the Mediterranean basin during Sahara dust storms
Atmospheric aerosols characterization over south-east italy from sunphotometer measurements
No full textAerosol Characterization by AERONET Sunphotometry
No full textAERONET sunphotometer measurements performed at the Physics Department of
Lecce’s University (Italy) (40° 20’ N, 18° 06’ E) are used to characterize aerosol
properties by aerosol optical depths (AOD), single scattering albedos (SSA),
Angstrom coefficients (Å), and fine (Nf) and coarse (Nc) number of particles per
cross section of the atmospheric column. AOD, SSA, Å, and Nf/Nc temporal plots
reveal that aerosol load, particle size distribution and chemical composition depend
on seasons and lead to assume that higher aerosol loads with a predominant
contribution of small, absorbing particles dominate over south-east Italy in springsummer
Modeling of Sahara dust outbreaks over the Mediterranean by RegCM3: case studies
No full textThe regional climate model RegCM3 coupled with a radiatively active aerosol model with online feedback is used to investigate direct and semi-direct radiative aerosol effects over Sahara and Europe in a test case of July 2003
In Situ Samplings and Remote Sensing Measurements to Characterize Aerosol Properties over Southeast Italy
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