Development of a Noval High Spectral Resolution Lidar for Studies of the Effects of Aerosols on the Earth's Climate

PI: Kevin S. Repasky, Montana State University

Aerosols play an important role in the Earth�s complex climate system. The increased aerosol loading of the atmosphere due to anthropogenic sources produces a negative radiative forcing similar in magnitude to the positive radiative forcing associated with the increase in anthropogenic greenhouse gases. According to the Fourth Assessment Report (FAR) of the Intergovernmental Panel on Climate Change (IPCC), the radiative forcing due to aerosols currently has a �low level of scientific understanding�, resulting in the largest uncertainties in our understanding and modeling of the Earth�s climate system. The radiative forcing of aerosols depends on three coupled components of the climate system, including atmospheric aerosols, water vapor, and clouds. To better understand and model the role these atmospheric constituents play in the climate system, new observational instruments and techniques are needed to reduce these uncertainties. The NASA EPSCoR project is focused on the development of remote sensing tools to better understand the role played by the interaction of the aerosols, water vapor and clouds in the lower troposphere. A high spectral resolution lidar (HSRL) is under development based on novel optical filters and frequency locking techniques developed at Montana State University. The HSRL provides range resolved aerosol profiles. A water vapor differential absorption lidar (DIAL) has been developed at Montana State University and will be deployed along with the HSRL. The water vapor DIAL provides range resolved number density profiles of the water vapor. Finally, a sun/sky scanning solar radiometer as part of the NASA AERONET network and a two color aerosol lidar will also be deployed. These two instruments provide further information regarding the atmospheric distribution and type of aerosols and other important column integrated information including size distribution and optical depth. The data collected using this suite of instruments will be used to study the interaction of the aerosols, water vapor, and clouds. In particular, the hygroscopic growth of the aerosols near clouds will be studied in an effort to better understand the aerosol direct and indirect effects.