Publication Date

2012-04-25

Availability

Open access

Embargo Period

2012-04-25

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Physics (Arts and Sciences)

Date of Defense

2012-03-30

First Committee Member

Kenneth J. Voss

Second Committee Member

Howard R.Gordon

Third Committee Member

Olga Korotkova

Fourth Committee Member

Paquita Zuidema

Abstract

Optical and chemical properties of size-resolved aerosols in near-surface air at Tudor Hill, Bermuda were measured between July 2006 and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized with a Micro-pulse lidar (MPL) and a CIMEL automated sun-sky radiometer. The chemical species in size-segregated aerosols in marine air were compared with the surface level aerosol optical properties. The aerosol concentration, along with chemical components, was compared with the surface level wind speed and showed a significant correlation with the sea salt components. The non-sea salt components such as non-sea salt sulfate and ammonium did not show a correlation with the surface level wind speed. A comparison between scattering data at surface level with the extinction coefficient at the lowest altitude bin (75m) from the lidar inversion shows a consistent correlation but is quantitatively different. This quantitative discrepancy was explained based on the hygroscopic growth due to differences in relative humidity in measurement conditions. Aerosol optical properties measured near the surface were often significantly correlated with those averaged over the column. These include scattering by near-surface bulk aerosol at 530 nm versus column aerosol optical depth (AOD), near-surface sub-µm scattering fraction versus column averaged sub-µm scattering fraction, and the average angstrom exponent over column and lidar ratio derived using column integrated size distribution and complex refractive index. We also found that the single scattering albedo (ωo) measured at the surface by combining daily averages of the aerosol absorption and aerosol light scattering were in the same range as the instantaneous ωo retrieved for the column. The relative contribution of submicron aerosol light scattering to total aerosol light scattering is slightly higher in the column relative to the surface. Surface level wind speed was found to have a more important affect on bulk aerosol light scattering at the surface than in column.

Keywords

Aerosol; Absorption Coefficient; Scattering Coefficient; MPLNET; AERONET; Comparison of AOP at Surface and Column

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