9414808 Maring The overall objectives of AEROCE Theme 2 are: a) to characterize the physical and chemical properties of aerosols that are important to the radiative properties of the atmosphere and to climate; b) to investigate the processes that affect these properties; and c) to assess the relative importance of natural and human sources. To this end an intensive aerosol measurement program that focuses on the chemical, physical, and radiative properties of aerosols will be carried out over the NAO and their impact on the radiative balance in the marine atmosphere. The component of the program covered by this project will focus on measurements of: 1) aerosol concentrations and size distribution from 3nm to 15um; 2) aerosol light scattering, both total and backscatter at three wavelengths using an integration nephelometer; 3)aerosol optical absorption using an aethalometer (measured as part of a separate AEROCE Theme 2 Proposal, Savoie et al.) Both the aerosol size and optical scattering measurements will be made at various relative humidities to investigate the importance of atmospheric water vapor on the physical and optical properties of aerosols. The program will be carried out in a series of intensive field experiments at Barbados, Bermuda and in the Canary Islands. Measurements of the physical and optical properties of aerosols will be used to develop a climatology of these properties. In addition, we will use our measurements of these properties in conjunction with chemical and meteorological data produced by other AEROCE investigators to identify and quantify the contributions of various source regions and types. Our data, coupled with concurrent measurements of column radiation parameters will allow closure for the direct forcing terms in the radiative energy balance equations. The ultimate objective is to calculate the radiative forcing caused by the major aerosol components over the mid- and lo w- latitude North Atlantic and assess the relevance to climate. These measurements, when coupled to radiation models, will allow estimates of the climatic consequences of future emissions scenarios for major pollutant species.
