Jingyi Chen

Type

Text

Type

Dissertation

Advisor

Zhang, Minghua | Colle, Brian | Liu, Yangang | Khairoutdinov, Marat | Riemer, Nicole | McGraw, Robert

Date

2018-01-01

Keywords

Atmospheric physics | Aerosol-Cloud Interactions | Atmospheric chemistry | Cloud Microphysics | Cloud Modeling | Turbulent Entrainment-Mixing

Department

Department of Marine and Atmospheric Science

Language

en_US

Source

This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.

Identifier

http://hdl.handle.net/11401/78269

Publisher

The Graduate School, Stony Brook University: Stony Brook, NY.

Format

application/pdf

Abstract

Aerosol-cloud interactions are critical to understand the impacts of anthropogenic activities on weather and climate by altering cloud microphysical, precipitation, and radiative properties. However, the quantitative estimates of aerosol indirect effects still suffer from large uncertainties in climate models, and there remains a large discrepancy in estimates between climate models and observations. Two main reasons are 1) the lack of knowledge of the related processes and nonlinear relationships, and 2) the highly simplified but deficient parameterizations used in weather and climate models. Therefore, detailed quantitative studies with explicit microphysical processes are in need. For this purpose, a new cloud parcel model has been developed and used to investigate aerosol-cloud interactions, with emphasis on three related sub-topics: 1) regime dependence of aerosol-cloud interactions; 2) effect of cloud droplet spectral shape (dispersion effect); 3) turbulent entrainment-mixing processes. It is shown that combined consideration of droplet number concentration (Nc) and relative dispersion (ϵ) characterizes the regime dependence of aerosol-cloud interactions better than considering Nc alone. The new relationship between aerosols and ϵ further reconciles contrasting observations in literature and reinforces the compensating role of dispersion effect. This study also reveals two new phenomena in updraft-limited regime: 1) The “condensational broadening” of cloud droplet size distribution in contrast to the well-known “condensational narrowing” in the aerosol-limited regime; 2) Above the level of maximum supersaturation, some cloud droplets are deactivated in the updraft-limited regime but remain activated in the aerosol-limited regime. The work on turbulent entrainment-mixing processes includes two steps: firstly, a new entraining parcel model is built on the adiabatic model, and then various effects of turbulent entrainment-mixing processes on microphysics are explored. In particular, entrained aerosols from the environmental air are treated with a new approach that does not increase computational expense too much and has the potential of being used as a parameterization in weather and climate models. The effects of entrainment rate and entrained aerosols on microphysics and aerosol-cloud interactions have been investigated. It is found that the impact of entrained aerosols on Nc can be as large as those of initial Na and new activation of small particles can significantly impact ϵ. | 174 pages

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