Assessing and Improving Active and Passive Ground Based Remote Sensor Techniques to Explore Aerosol-Cloud Interaction in Urban Environments

In this paper, we explore using ground based passive and active remote sensing, the Twomey Indirect Effect which states that the droplet size of water phase clouds will decrease with increasing aerosols for a certain liquid water path. Here, cloud droplet size is obtained from a combination of COD from the diffuse transmittance of a Multi Filter Rotating Shadow band Radiometer (MFRSR) and the cloud LWP from a Microwave Radiometer (MWR) while the aerosol properties are obtained near cloud base from a Light Detection and Ranging (LIDAR) system. Our preliminary results show that urban aerosol loading can modify the cloud effective radius within theoretical limits. In addition, we show that a simplified dual channel approach in analyzing the MWR LWP can be used instead of the NN approach. Furthermore, we show the importance that the aerosol optical properties need to be measured near cloud base. Finally, we explore the potential of modifying our approach to remove the noisy and difficult measurement of Raman LIDAR derived extinction with calibrated LIDAR backscatter. The result seem to show a general improvement in correlation and offer the possibility of increasing the number of cases observed.

Keywords: aerosol; cloud optical depth; cloud droplet effective radius; integrated liquid water path; transmittance; Aerosol-Cloud Index; Backscatter.

Address all correspondence to: Zaw Han, City University of City College of New York, Electrical Engineering Department, 140th Street & Convent Avenue, New York, NY 10031 USA; Phone: 212-650-7000 Fax: 212-650-8249; Email;zhan@ccny.cuny.edu

Barry Gross, City University of City College of New York, Electrical Engineering Department, 140th Street & Convent Avenue, New York, NY 10031 USA; Phone: 212-650-5325; Fax: 212-650-8249; Email: eebmg@yahoo.com