Indirect radiative forcing due to aerosols over the North Atlantic region.

Informazioni relative al progetto

ACE-2: CLOUDYCOLUMN

ID dell’accordo di sovvenzione: ENV4950117

Progetto chiuso

Data di avvio 1 Gennaio 1996

Data di completamento 31 Dicembre 1998

Finanziato da

• Specific programme of research and technological development in the field of environment and climate, 1994-1998

Costo totale

Nessun dato

Contributo UE

Nessun dato

Coordinato da

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
France

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Risultati finali

Airborne data set on physical properties of aerosols and cloud condensational nuclei, cloud dynamical, microphysical and radiative properties, during the ACE-2 campaign

Summary: The CLOUDY-COLUMN data set comprises precise and complete information about the physical properties of aerosols and cloud condensation nuclei, about dynamical and microphysical properties of stratocumulus clouds, and about their radiative properties measured with multi-directional and multispectral radiometers and a lidar. This data set is open to the international scientific community and can be used for research purposes. Detailed analysis has been already performed and original results have been obtained on closure experiments for the aerosol activation process, the droplet growth in stratocumulus clouds and the microphysics/radiation interaction. The results have been published in journals and they can be used by climate modellers for development and validation of parameterizations of the indirect effect of aerosols on climate. Main preliminary outcomes of the project are: (i) a good agreement between CCN activation spectra measured at cloud base and droplet number concentrations measured in clouds, while there is still discrepancy between the droplet concentration derived from aerosol properties with an activation model and the values measured in cloud; (ii) a statistical analysis of the frequency distributions of droplet number concentration for pure marine and polluted air masses; (iii) a statistically significant description of the vertical profiles of droplet sizes, that validates the adiabatic model of droplet growth; (iv) a comparison between remote sensing measured values of cloud optical thickness and values derived with the adiabatic model, that validates the adiabatic model of radioactive transfer calculations; (v) an observational evidence of the aerosol indirect effect with remote sensing measurements of multispectral cloud reflectances; (vi) the development of a novel parameterization of cloud optical properties, based on droplet number concentration instead of droplet effective radius.

Spatial variability of stratocumulus cloud optical thickness and validity of the Independent Pixel Approximation

Summary: The POLDER measurements of the bi-directional reflectrance distribution function have been analyzed to derive the cloud optical thickness all along the flight patterns. Thanks to POLDER angular sampling capability, the independent pixel approximation (IPA) has been tested and validated for these particular clouds. The droplet effective diameter has been derived from POLDER observations.