Airborne HSRL Aerosol, Ice, and Cloud Observations During ARCTAS/ISDAC

Richard Ferrare NASA LaRC
Chris Hostetler NASA - Langley Research Center
John Hair NASA - Langley Research Center
Anthony (Tony) Cook NASA - Langley Research Center
David Harper NASA - Langley Research Center
Sharon Burton NASA - Langley Research Center
Michael Obland NASA - Langley Research Center
Raymond Rogers NASA - Langley Research Center
Amy Scarino Science Systems and Applications, Inc.
David Turner National Oceanic and Atmospheric Administration
Norm ONeill Université de Sherbrooke
Peter Colarco NASA

Category: Aerosol Properties

Working Group: Aerosol Life Cycle

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Measurements acquired in the vicinity of the ARM NSA site on April 9, 2008 during the ARCTAS/ISDAC campaigns. (Left) Airborne HSRL measurements (532 nm) of particulate backscatter (a), particulate depolarization (b), lidar ratio (c). (Right) ARM NSA MMCR measurements of radar reflectivity (d), particulate optical depth measurements from various sensors (e), and TSI image (f). The white vertical dashed line represents when the HSRL measurements were acquired directly over the NSA site (21:52 UT). The NASA B200 King Air flew from east (right) to west (left). The HSRL measurements of high particle depolarization (>0.3) and low lidar ratio (~20 sr) indicate the presence of ice. The MMCR measurements indicate cloud layers between ~1.5–5.5 km that are not obvious in the optical depth measurements or TSI image.

During the joint 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS)/Indirect and Semi-Direct Aerosol Campaign (ISDAC) field campaign, the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL) on the NASA B200 aircraft measured profiles of particulate extinction (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm). Particulate intensive parameters derived from HSRL data are used to infer specific particulate types and mixtures of those types. Combining the HSRL observations of the spectral ratio of depolarization and the particulate extinction/backscatter ratio (“lidar ratio”) are shown to help discriminate ice and dust. The HSRL measurements are used in conjunction with surface-based remote sensing measurements from the ARM Climate Research Facility’s NSA site to investigate particles over Barrow. The HSRL measurements show that extensive layers of ice crystals can contribute significantly to particulate optical depth derived from surface-based passive measurements. During some instances, coincident MMCR radar observations indicated extensive cloud layers while Sun photometer, NIMFR radiometer, and TSI images showed little or no indication of clouds. The suite of active and passive remote sensing observations suggest that (1) ice crystals of various sizes were present, (2) coincident measurements from active sensors such as HSRL greatly aid in the interpretation of particulate optical depth measurements from passive instruments, and (3) coarse-mode aerosol optical depth derived from the Sun photometer data may provide an indication of the optical depth due to ice particles. In addition, the HSRL measurements are also used to evaluate the simulations of aerosol/cloud distributions from the NASA GEOS-5 general circulation model and assimilation system. The GEOS-5 median particulate extinction profiles are shown to be in good agreement with the corresponding median HSRL extinction profiles. The HSRL measurements indicated that particulate optical depth of elevated layers composed a much higher fraction (>40–50%) of total optical depth than observed in HSRL measurements acquired at lower latitudes on previous campaigns. Biomass burning smoke was found to provide the largest contribution to particulate optical thickness.

http://science.larc.nasa.gov/hsrl/index.html

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