Date: Thursday, April 19, 2012
Time: 8:00 am
Location: PHYS 401
TITLE:
Retrieval of microphysical properties of aerosols from a hybrid multiwavelength lidar dataset
ABSTRACT:
Aerosols continue to pose one of the largest uncertainties in the global models utilized to assess different climate change scenarios. In particular, models still fail to represent the vertical distribution of aerosols in the atmosphere with reasonable accuracy.
Currently, most aerosol measurements and retrievals from either spaceborne or ground-based instruments reflect the contribution of the total atmospheric column and therefore do not provide information on the aerosol vertical distribution. Lidar (light detection and ranging) systems are of particular interest in that respect, as they are able to provide profiles of optical properties of aerosols, such as backscatter and extinction coefficients, with high spatial and temporal resolution. Furthermore, it has been demonstrated that from backscatter and extinction coefficient profiles at multiple wavelengths it is possible to retrieve physical properties of aerosols such as effective radius, surface-area, number and volume distributions, complex index of refraction and single scattering albedo.
Most studies to test and validate the inversion algorithm scheme for multiwavelength lidar data have been restricted to the combination of the elastic and Raman scattering measurements from ground-based systems that were carefully designed to emit and receive signals in the same optical path. For this work I propose a new combination of lidar measurements, comprising airborne HSRL (High Spectral Resolution Lidar at 532 nm + 1064 nm elastic channel - nadir viewing) and ground-based elastic and Raman measurements (at 355 nm - zenith viewing). In this new geometry, HSRL measurements within 5 km of the ground-based systems are regarded as collocated measurements. By combining different lidar retrieval techniques to obtain the optical dataset at multiple wavelengths necessary to retrieve the aerosol microphysical properties, and by adding a horizontally averaged component from the geometry of the problem, I will be exploring the feasibility of utilizing this new methodology for test and validation of the retrieval algorithms in the framework of future field campaigns employing synergistic airborne and ground-based lidar measurements, and also for a future spaceborne multiwavelength lidar mission.