Dynamics of monsoon depressions in a warming climate
Monsoons are large-scale summertime weather systems that provide rainfall to half the global population. Monsoons are vital for agriculture and societies in Asia, Africa, Australia, and the Americas, and are expected to change dramatically in future decades due to global warming. To enable vulnerable regions adapt to changes in monsoons, it is essential to understand how monsoon rainfall will respond to climate change. However, predictions from climate models are highly uncertain. For example, there is no agreement between models on whether monsoon rainfall over India will increase or decrease as climate warms.
Monsoon depressions are a key source of this uncertainty. These are low-pressure systems approximately 2000km in size that deliver 40% to 80% of total rainfall to some monsoon regions. There is limited understanding of the dynamics of monsoon depressions in today’s climate and how they will respond to global warming is largely unknown. This PhD project will bring together experts on atmospheric dynamics and climate science in a new collaboration that will transform our understanding of monsoon depressions in a warming climate using novel computational modelling. The first objective is to advance fundamental knowledge of monsoon depressions using simplified dynamical models. The second objective is to use these new insights – together with a suite of state-of-the-art, high-resolution climate simulations – to deliver robust predictions for the behaviour of monsoon depressions in a warming climate and their impact on vulnerable regions.
Part 1: While detailed observations and comprehensive models reveal the richness of structure of atmospheric phenomena, many of the great leaps in our understanding of the fundamental dynamical processes have resulted from the careful use of idealised models of particular flow patterns. In this spirit, Part 1 of the PhD project will use simplified numerical models of monsoon depressions to investigate the dynamical processes that govern their propagation and their response to climate change. Despite the importance of monsoon depressions for global water resources, dynamical understanding of these systems is only starting to develop and there is much to be learned through the use of simplified models of this kind.
Part 2: While monsoon depressions are the primary source of water in many regions, reliable projections of how monsoon depressions will change with climate have been elusive because current climate models lack the resolution to properly simulate these systems. However, rapidly increasing computational power now means that climate models with sufficient resolution to simulate monsoon depressions are becoming feasible. Simulations at a resolution of 50km have recently been shown to capture the essential features of monsoon depressions suggest a poleward shift in the regions where monsoon depressions form as climate warms. However, it is unclear how other features of monsoon depressions – for example frequency of occurrence or strength – will respond to a warming climate. In Part 2 of the project the dynamical understanding of monsoon depressions developed in Part 1 will be combined with analyses of state-of-the-art high-resolution climate simulations to deliver robust projections for monsoon depressions in a warming climate.
Together Parts 1 and 2 of this PhD project comprise a comprehensive investigation of monsoon depressions. Ultimately this project will advance our fundamental understanding of the dynamics of monsoon depressions and deliver robust monsoon projections to help vulnerable regions prepare for and mitigate the impacts of climate change.
More project detail can be found here: https://synergy.st-andrews.ac.uk/earthsci/files/2019/03/St-Lenoards-Funded-Project-Mike-Byrne-.pdf
Training and skills This St Leonard’s College Interdisciplinary Studentship will provide training in monsoon dynamics, climate science, computational modelling, numerical methods, coding and Big-Data analysis. The student will be a member of both the Climate and Global Change research group in the School of Earth & Environmental Sciences and the Vortex Dynamics research group in the School of Mathematics & Statistics. In addition to the specific training received through the PhD, the student will have the opportunity to improve general transferrable skills through University courses run by CAPOD, external research workshops, and presentations at group meetings. The student will also have the opportunity to attend and present their research at national conferences, and at least one international conference.
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