Wednesday, 25 January 2012: 11:30 AM
Quantifying the Aerosol-Cloud Interaction From Ground Based Observations
Room 244 (New Orleans Convention Center )
Aerosol interaction and modification of cloud properties is poorly understood quantitatively resulting in the largest uncertainty in Earth's radiation budget for climate studies. In this presentation, we investigate direct ground based methods to assess this interaction which are crucual for simultaneous aerosol and cloud property measurments. This is in contrast to space-borne retrievals which are constrained to either aerosol or cloud measurements relying completely on indirect correlations between aerosols and clouds. In this direction, we will discuss the development of a combined Multi-Filter Rotating Shadowband Radiometer (MFRSR) and Microwave Radiometer (MWR) system for real-time monitoring of the atmospheric aerosols and clouds. For quantifying the aerosol-cloud interaction mechanism, simultaneous observations of cloud water droplet properties as well as aerosol properties below the clouds are essential. The associated uncertainty in cloud retrievals from the combined MFRSR-MWR system due to the sensitivity of various parameters and the need to assess the band correction in the solar aureole region using radiative transfer accounting for the blocked band geometry will be discussed. An iterative approach combining the simultaneous observations from MFRSR-MWR system to retrieve the Cloud Optical Depth (COD) and Cloud Droplet Effective Radius for thick cloud cases will be validated with the satellite observations. Our approach will be thoroughly validated with the available cloud products from the ARM Southern Great Plains (SGP) site both with ground and operational satellite (MODIS and GOES) retrievals before adopting for observations over New York City area. Finally, we explore cloud droplet size spectra and the effect of aerosols on cloud properties from the direct estimates of COD when combined with MWR measurements.