The effects of model resolution on the South Asian and West African monsoons in the Pliocene

Williamson, Andrea (2022) The effects of model resolution on the South Asian and West African monsoons in the Pliocene. Doctoral thesis, University of East Anglia.

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Abstract

The Pliocene Epoch (5.33 – 2.58 Million years ago) is currently being used as a future climate change analogue due to CO2 levels during this time which are close to those of the present day, similar continental configuration between the two and a wealth of paleoenvironmental proxy data available. However, most model simulations involving the Pliocene are run at coarse resolution and include many boundary condition changes from the present day.

This thesis examines the effects of increased model resolution on the Pliocene climate using an atmosphere-only, spectral global climate model (the IGCM4) with the sea surface temperature field as the only boundary condition change between Pliocene and present day. Using the present day as a control experiment, basic state differences between the Pliocene and present day are explored. Then, a step-change approach is utilised: first, the dynamical resolution of the model is increased while the topography field remains constant (at low resolution). A further step follows to additionally increase the resolution of topography (to high resolution), in order to separate these two effects of increased resolution.

Two monsoon systems are examined - the South Asian monsoon (SAM) and the West African monsoon (WAM). Dynamical differences are found between Pliocene and present day for the SAM region, affecting monsoonal circulation. A northward shift in climatic features is observed with increased dynamical resolution, while the effects of topographic resolution are confined to the immediate area surrounding certain topographic features. Resolution effects are found to have varying effects regionally, with dynamical resolution generally being more important than topography.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Chris White
Date Deposited: 15 Jun 2022 09:35
Last Modified: 15 Jun 2022 09:35
URI: https://ueaeprints.uea.ac.uk/id/eprint/85627
DOI:

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