Absorbing aerosols and their effect on cloud absorption and forcing is among the most difficult to measure at the global scale. MFRSR and CIMEL atmospheric monitoring instruments are already being deployed for real time AOD (aerosol optical depth) measurements and the corresponding retrieval of fine and coarse mode distributions along with ozone and water vapor concentrations. To complement the instruments, modeling methods have been employed to fill the gaps where measurements are not available and provide air quality predictions that can be used for forecasts as well as a better understanding of the interplay of meteorology, atmospheric emissions and chemistry. In particular, for the New York State area, the New York State Department of Environmental Conservation (NYSDEC) uses Community Multi-scale Air Quality (CMAQ) model to couple meteorology to local emissions and there is intense interest in trying to assess the model performance beyond current surface network measurements. Preliminary results of CMAQ model intercomparison with sunphotmeters indicate that the column AOD in the model is underestimated illustrating that there is a general underestimation of ultrafine (aitken) particulates which can dramatically affect health and therefore needs to be investigated and better assessed in the model. This paper presents comparisons between the fine mode and coarse mode aerosols measured by MFRSR, CIMEL and CMAQ model during the Intensive Observational Period at BNL during the summer of 2011. During this campaign simultaneous measurements of chemical, physical and optical properties of aerosols were measured for 10 weeks with a suite of more than 20 environmental monitoring instruments. The transportation of aerosols was evaluated using the Hysplit model. In addition to improving the understanding of aerosol modeling the authors intend to expand the applications of the existing sunphotometers to retrievals of single scattering albedo. The addition of this new retrieved parameter will result in a better understanding of the contribution of absorbing aerosols on radiative forcing.