The oceanic fingerprints on changing monsoons over South and Southeast Asia


Increasing severity of floods and droughts under climate change are a major societal challenge. As moisture fluxes increase in a warming climate, the contrast between wet and dry meteorological regimes, seasons and extreme events amplifies [1]. This research will focus on changes in the hydrological cycle of the Indian Peninsula and Maritime Southeast Asia, where monsoon rainfall is largely fed by moisture from the ocean [2]. Understanding and quantifying changes in the monsoons and tropical rain bands driven by oceanic warming are of paramount importance as new extremes, such as the recent devastating flooding events in Pakistan, impact hundreds of millions of people. Whilst thermodynamic responses of the hydrological cycle under global warming are relatively well known, the atmospheric moisture transport response to ocean warming is complex and much less understood due to numerous atmospheric and oceanic feedbacks that are involved. Using a variety of models and observations, the student will use and develop novel methods to explore how ocean warming is changing the regional hydrological cycle through shifts in evaporation and atmospheric moisture transport over the tropical Indian and Western Pacific oceans – the oceanic ‘fingerprints’ on changing monsoons.



The research will use three state-of-the-art methodologies/techniques recently applied to assess changes in the global and regional hydrological cycles: a) the water mass transformation method [1], applied here to reveal large-scale water cycle changes inferred from changes in the hydrological properties of the tropical Indian and Western Pacific oceans; b) moisture budget analysis [2] and c) Lagrangian trajectories of water masses (TRACMASS) [3], applied here to assess how ocean warming drives evaporation increases and controls moisture transport from ocean to land. The research will focus on the driving mechanisms of long-term changes in the oceanic and atmospheric parts of the regional hydrological cycle which control the monsoon regime and the location/intensity of the tropical rain band. The student will quantify changes in the regional hydrological cycle in the recent past and future, using various observational (in-situ/satellite-derived) datasets, ocean/atmospheric re-analysis products, and climate model projections. In particular, use of the new Ocean Mixed Layer coupled Met Office Unified Model well-resolving air-sea interactions, and the NOC/Met Office high resolution coupled climate model capturing changes in hydrological cycling at synoptic scale, will enable us to follow the fine-structure pathways of moisture from specific oceanic moisture source regions to South and Southeast Asia.



The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the University of Southampton. Specific training will include: training in the use of parallel computing, programming languages (Python, Matlab, Ferret, …); how to access and analyse state-of-the-art climate model data via national resources; use of statistical methods to detect and attribute climatic trends and innovative diagnostics to interpret changes in the hydrological cycle that are projected in climate models; collaboration with Indian and Vietnamese colleagues and stakeholders, expanding related current collaborations of the supervisors in the framework of two recently funded research programmes. The student will be actively encouraged to attend and present their work at national and international conferences.


Eligibility & Funding Details: 

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Background Reading: 

[1] Skliris, N., Zika, J. D., Nurser, G., Josey, S. A., and Marsh, R. (2016). Global water cycle amplifying at less than the Clausius-Clapeyron rate. Scientific Reports, 6, 38752. DOI: 10.1038/srep38752

[2] Skliris N., et al. (2022). Drivers of rainfall trends in and around Mainland Southeast Asia. Frontiers in Climate (in press). DOI: 10.3389/fclim.2022.926568

[3] Dey, D., Döös, K. (2021). Tracing the origin of the South Asian Summer Monsoon precipitation and its variability using a novel Lagrangian framework. Journal of Climate, 34(21): 1-40. DOI:  0.1175/JCLI-D-20-0967.1