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Thursday 27 May 20211st year Phd talks

Thomas Hutton and Daniel Williams -

online 13:30-14:30

Speaker: Thomas Hutton

Title: A Lagrangian view of the evolution of convective updrafts

Abstract: The representation of cumulus convection is one of the largest sources of uncertainty in current weather and climate models. Where resolutions are too coarse to accurately model convection, parameterizations of the small-scale convective processes are required. High resolution large eddy simulations (LES) can be used to diagnose air parcel trajectories, their momentum and heat budgets, as well as representing entrainment. However, this is a computationally expensive process. This project aims to bridge the gap between current models and LES by developing a stochastic Lagrangian model to represent an ensemble of air parcels. The motions of each parcel would be explicitly modelled, with 3-D turbulence being represented by stochastic terms. A key question of this project is to compare the model results against the statistics of LES results as a measure of the model’s success, allowing for a deeper understanding on how to accurately model convective processes. The model results may then be simplified or adapted to resemble parameterization systems within current models, allowing for guidance on how current parameterizations may be improved upon. This talk will cover some preliminary work in adapting a single-column Lagrangian dispersion model within a convective boundary layer.

Speaker Daniel Williams

Title: Developing an Idealised Climate Model of Titan

Abstract: Our understanding of Saturn's moon Titan has substantially increased over the past 15 years with the successful Cassini-Huygens missions, however a number of unknowns still exist with respect to understanding the moon's atmospheric dynamics and climate. Titan is the only terrestrial Solar System body aside Earth to possess a dense atmosphere and evidence of an active hydrological cycle, but direct observations of the atmosphere and surface are substantially hindered by the moon's thick haze layer. This presents an ideal opportunity to use climate models to develop a more complete understanding of the dynamics of the atmosphere, constrained by existing observational data; thereby providing a more complete picture in time for the arrival of the upcoming NASA Dragonfly mission in 2036. Using and adapting the existing Isca climate model developed here in Exeter, we aim to build an idealised representation of Titan that can capture most of its observed features including seasonal variation, with the intention of testing various properties such as its stability against a runaway greenhouse scenario.

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