Combining Passive Polarimetric and Lidar Observations from TCAP to Vertically Partition a Multi-Modal Aerosol Model
Abstract
The first airborne deployment associated with the Two-Column Aerosol Project (TCAP) field campaign was carried out on Cape Cod, Massachusetts during July 2012 using the DOE Gulfstream 1 (G-1) and the NASA Langley B200. The first column located on Cape Cod has the surface based ARM Mobile Facility, which measures aerosol properties, radiation, and cloud characteristics, as its anchor point. The second column, 200 km to the East, was chosen to facilitate characterization of the large gradient of AOD near the coast of New England. The G-1 was equipped with a suite of in situ instrumentation to measure the size, composition and optics of aerosols, together with spectral Aerosol Optical Depth (AOD) above the aircraft using the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research. The G1 generally flew at low altitude except when profiling the two columns. The B200, flew at ~ 9 km, above the G1, and operated the world's first airborne three backscatter (355, 532 and 1064 nm) and two extinction (355 and 532 nm) channel high-spectral-resolution lidar, HSRL-2 and the Research Scanning Polarimeter (RSP), which provides multi-angle multi-spectral observations of the intensity and polarization over a spectral range from 410 to 2260 nm. The TCAP measurements are ideal for remote sensing of aerosols since a dark ocean allows the full power of the passive intensity and polarization observations to be explored. RSP observations over the ocean have previously been used to retrieve the AOD, particle size and complex refractive index of aerosols, but it was noted that the vertical distribution of the aerosols could affect the accuracy of the retrieval. In this paper we combine HSRL-2 and RSP data to retrieve and partition a multi-modal aerosol model through the column. The lidar intensive variables (ratios of the lidar observations) that do not depend on aerosol load are used to constrain the microphysics of the aerosol modes. Where the classification technique presented in Burton et al. (2012) identifies layers of distinct aerosol types that information is used in defining the layering of the forward model that is used in the iterative inversion. The HSRL-2 extinction measurements are then used to define the opacity of the vertical layers and an iterative search is executed to find the aerosol types that best match all the RSP observations, while still being compatible with the lidar observations within their associated uncertainties. Other approaches to using such sophisticated lidar measurements are clearly possible and we expect to compare our method with both other analyses of the lidar data and also the in situ and spectral AODs obtained by the G1.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A13K0339C
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0360 ATMOSPHERIC COMPOSITION AND STRUCTURE / Radiation: transmission and scattering;
- 3360 ATMOSPHERIC PROCESSES / Remote sensing