PhD Studentship: Quantifying Raindrop-Freezing Fragmentation Using a Cloud Chamber and Numerical Modelling

Department: Earth and Environmental Sciences
Title: Quantifying Raindrop-Freezing Fragmentation Using a Cloud Chamber and Numerical Modelling
Application deadline: All year round
Research theme: Atmospheric Science

How to apply: uom.link/pgr-apply-2425

Number of PhD positions: 1

This 3.5 year PhD is funded by the Department of Earth and Environmental Sciences, available for Home students only. Tuition fees will be paid and you will receive a tax free allowance set at the UKRI rate (£19,237 for 2024/25) with and extra £1000 RTSG per annum. We expect the stipend to increase each year. 

A cloud chamber, an experimental apparatus that replicates atmospheric cloud conditions, provides a controlled environment to study raindrop-freezing fragmentation under varying thermodynamic conditions. Complementing these experiments with numerical modelling can enhance our understanding of the microphysical and thermodynamic parameters governing the fragmentation process and its implications for cloud microphysics and climate modelling.

Objectives

The primary objective of this PhD project is to quantify raindrop-freezing fragmentation using a cloud chamber and support these findings with numerical modelling. Specific aims include:

Experimentally investigate the relationship between raindrop size, freezing rate, and fragmentation outcomes under controlled cloud chamber conditions.

Identify the thermodynamic and microphysical parameters (e.g., temperature, humidity, collision processes) that influence fragmentation.

Develop and validate a numerical model to simulate raindrop-freezing fragmentation and its contribution to secondary ice production.

Integrate experimental and modelling results to improve parameterizations of SIP in atmospheric models.

Methodology

1. Experimental Work in a Cloud Chamber

The experimental component will use a state-of-the-art cloud chamber at the University of Manchester to replicate atmospheric conditions. The methodology includes:

Raindrop Formation and Freezing: Generate raindrops of varying diameters using a droplet generator. Expose them to subzero temperatures to induce freezing.

Fragmentation Observation: Use high-speed cameras and laser imaging systems to record and analyze the freezing process and the resulting fragments.

Parameter Control: Systematically vary temperature, humidity, and pressure to simulate different atmospheric conditions. Introduce wind shear and turbulence to study their effects on fragmentation.

Data Collection: Measure the size, number, and velocity of ice fragments using advanced particle imaging tools

2. Numerical Modelling

A numerical model will be developed to simulate the freezing and fragmentation process. The steps include:

Model Development: Develop a high-resolution numerical model based on the principles of thermodynamics, fluid dynamics, and ice nucleation physics.

Input Parameters: Use experimental data to constrain input parameters such as drop size, freezing rate, and ambient conditions.

Model Validation: Compare model predictions with experimental results to validate accuracy.

Sensitivity Analysis: Conduct sensitivity analyses to identify critical parameters influencing fragmentation.

Applicants should have, or expect to achieve, at least a 2.1 honours degree or a master’s (or international equivalent) in a relevant science or engineering related discipline. This project is open to home students.

Please contact the supervisor, Dr Paul Connolly - paul.connolly@manchester.ac.uk, for this project before you apply. Please include details of your current level of study, academic background and any relevant experience and include a paragraph about your motivation to study this PhD project.

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