Date of Award

2021

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Administrative Home Department

Department of Physics

Advisor 1

Claudio Mazzoleni

Committee Member 1

Jacek Borysow

Committee Member 2

Will Cantrell

Committee Member 3

Simon Carn

Abstract

Aerosol and water are inexorably linked, and both are ubiquitous within our atmosphere and required components for cloud formation. Relative humidity (RH), a temperature dependent quantity, can have a significant influence on the size, shape, and ultimately, the optical properties of the aerosol. RH can vary substantially on small spatial and short temporal scales in turbulent conditions due to rapid fluctuations in temperature and water vapor mixing ratio. Accurate assessment of optical enhancements due to an increase in RH is key for determining the particles’ impact on the climate and visibility.

A humidity-controlled cavity attenuated phase-shift albedometer (H-CAPS-PMSSA) was designed and characterized to measure the humidity response of aerosol extinction and scattering. Size-dependent truncation, a significant source of systematic bias within the H-CAPS-PMSSA, was characterized and a correction scheme developed. The H-CAPS-PMSSA was then used to determine the optical and hygroscopic properties of ammonium sulfate, nigrosin, and two mixtures of ammonium sulfate and nigrosin. It was determined that enhancements in single scattering albedo of these aerosol because of humidification could be approximated using a quadratic function with a single fitting parameter related to the hygroscopicity of the two species in the mixture.

To determine RH in a turbulent environment, non-invasive temperature measurements are necessary. Temperature can be inferred from vibro-rotational Raman (VRR) scattering. Several methods of extracting temperature from the VRR spectra of N2 and O2 were investigated. It has been shown that the non-rigidity of N2 and O2 must be considered for accurate temperature measurement and that methods involving more VRR lines, and therefore greater photon statistics, had the greatest precision and self-consistency. It was also found that separation between the lines was an important consideration for temperature measurement precision.

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