Evaluation of LIDAR/Polarimeter Aerosol Measurements by In Situ Instrumentation during DEVOTE

Combined measurements from LIDAR (LIght Detection And Ranging) and polarimeter instruments provide the opportunity for enhanced satellite observations of aerosol properties including retrievals of aerosol optical depth, single scattering albedo, effective radius, and refractive index. However, these retrievals (specifically for refractive index) have not been fully vetted and require additional intercomparisons with in situ measurements to improve accuracy. Proper validation of these combined LIDAR/polarimeter retrievals requires evaluation in varying atmospheric conditions and of varying aerosol composition. As part of this effort, two NASA Langley King Air aircraft have been outfitted to provide coordinated measurements of aerosol properties. One will be used as a remote sensing platform with the NASA Langley high-spectral resolution LIDAR (HSRL) and NASA GISS research scanning polarimeter (RSP). The second aircraft has been modified for use as an in situ platform and will house a suite of aerosol microphysical instrumentation, a pair of diode laser hygrometers (DLHs) for water vapor and cloud extinction measurements, and a polarized imaging nephelometer (PI-Neph). The remote sensing package has flown in a variety of campaigns, however only rarely has been able to coordinate with in situ measurements. The use of two collocated aircraft will allow for future coordinated flights to provide a more complete dataset for evaluation of aerosol retrievals and allow for fast-response capability. Results from the first coordinated King Air flights as part of DEVOTE (Development and Evaulation of satellite ValidatiOn Tools by Experimenters) will be presented. Flights are planned out of Hampton, VA during September and October 2011 including underflights of the CALIPSO satellite and overflights of ground-based AERONET (AErosol RObotic NETwork) sites. These will provide a comparison of aerosol properties between in situ and remote instruments (ground, aircraft, and satellite-based). In situ measurements include aerosol number density, size, scattering, absorption and hygroscopicity (aerosol scattering as a function of relative humidity). The PI-Neph will provide the first airborne in situ measurements of aerosol polarized phase function for comparison to the RSP retrievals. As this is the first airborne use of the PI-Neph, aerosol scattering measurements from the PI-Neph will be compared to an integrating nephelometer to provide a primary indication of instrument functionality. Specific flights will be performed to study a range of aerosol classifications including fresh anthropogenic pollution (flights over populated regions), aged pollution (tracking pollution as it moves off shore), sea salt (low altitude ocean flights by the in situ aircraft) and biogenic (flights over forest canopies). In addition, the DLH and a wing-mounted cloud aerosol precipitation spectrometer will provide insight into aerosol retrievals above and near clouds.