Four Years of Continuous Surface Aerosol Measurements from the Department of Energy's Atmospheric Radiation Measurement Program Southern Great Plains Cloud and Radiation Testbed Site

explained by the indirect aerosol cloud effect. The use of a parcel model to determine the cloud droplet number concentration enables us to separate the effects of the cloud LWP and cloud droplet number concentration on the cloud optical depth. An examination of the TOA shortwave flux from the radiative transfer model applied to the two sites does not directly confirm the indirect effect, because the observed surface albedos at the NSA site for our cases (0.6 ^ 0.28) are significantly larger than those from the SGP site (0.2 ^ 0.02). However, the model can be used to estimate the outgoing flux difference if the clouds from the NSA site had the same average surface albedo and average zenith angle as those from the SGP site (see Fig. 3). This analysis indicates that these sites provide important evidence corroborating the effect of aerosols on cloud optical properties and on shortwave fluxes at both the surface and the TOA. Moreover, the analysis indicates that a parameteriza-tion of the effects of aerosols on clouds on the basis of an adiabatic parcel model and average aerosol size distributions such as those used in current general circulation models 18,22,23 provides a good estimate of cloud optical properties determined over a broad range of aerosol concentrations. A microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climate. properties of stratiform clouds deduced from ground-based measurements. of microphysical and shortwave radiative properties of boundary layer stratus from ground-based measurements. Arctic stratus cloud properties and their effect on the surface radiation budget: selected cases from FIRE ACE. A new retrieval for liquid water path using a ground based microwave radiometer and measurements of cloud temperature. Arctic stratus cloud properties and radiative forcing derived from ground-based data collected at Barrow Alaska. study of cloud droplet nucleation and in-cloud sulfate production during the Sanitation of the Atmosphere (SANA) 2 campaign. A three-year record of simultaneously measured aerosol chemical and optical properties at Barrow, Alaska. The regional analysis system for the operational " early " eta model: original 80-km configuration and recent changes. Radiative properties of boundary layer clouds: droplet effective radius versus number concentration. Estimation of water cloud properties from satellite microwave, infrared, and visible measurements in oceanic environments. 1, Microwave brightness temperature simulations. Evaluation of aerosol indirect radiative forcing in MIRAGE. Acknowledgements We thank P. Quinn for providing the composition data …

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